Transfer decoder to new reader

Make decoder's `Image` an option

.github/workflows/rust.yml

@@ -11,7 +11,7 @@ jobs:
       matrix:
         rust: ["1.88.0", stable, beta, nightly]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
 
     - uses: dtolnay/rust-toolchain@nightly
       if: ${{ matrix.rust == '1.88.0' }}
@@ -32,13 +32,29 @@ jobs:
       if: ${{ matrix.rust != '1.88.0' }}
       run: cargo test -v && cargo doc -v
 
+  test-platforms:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, ubuntu-24.04-arm, macos-latest, macos-26-intel, windows-latest, windows-11-arm]
+    steps:
+    - uses: actions/checkout@v6
+    - uses: dtolnay/rust-toolchain@stable
+    - name: Cache Cargo Dependencies
+      uses: Swatinem/rust-cache@v2
+      with:
+        cache-on-failure: true
+    - name: test
+      run: cargo test -v
+
   features:
     runs-on: ubuntu-latest
     strategy:
       matrix:
         feature: ["", deflate, jpeg, lzw, zstd, default, "default,zstd"]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@stable
       with:
         components: clippy
@@ -59,25 +75,29 @@ jobs:
       matrix:
         arch: [powerpc-unknown-linux-gnu, i686-unknown-linux-gnu]
     steps:
-      - uses: actions/checkout@v4
-      - name: Install or use cached cross-rs/cross
-        uses: baptiste0928/cargo-install@v2
-        with:
-          crate: cross
+      - uses: actions/checkout@v6
+      - uses: taiki-e/install-action@cross
       - name: Cache Cargo Dependencies
         uses: Swatinem/rust-cache@v2
         with:
           cache-on-failure: true
           key: ${{ matrix.arch }}
-      - name: Start Docker (required for cross-rs)
-        run: sudo systemctl start docker
       - name: Cross-Run Tests using QEMU
         run: cross test --target ${{ matrix.arch }}
 
+  msrv:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v6
+    - uses: dtolnay/rust-toolchain@stable
+    - uses: taiki-e/install-action@cargo-hack
+    - name: Check MSRV
+      run: cargo hack check --rust-version
+
   rustfmt:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@stable
       with:
         components: rustfmt
@@ -87,8 +107,8 @@ jobs:
   clippy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
     - uses: dtolnay/rust-toolchain@stable
       with:
         components: clippy
-    - run: cargo clippy --all-features # TODO: enable "-- -D warnings" once all outstanding clippy lints are fixed
+    - run: cargo clippy --all-features --all-targets -- -D warnings

CHANGES.md

@@ -11,6 +11,12 @@ Changes:
   directory state if they fail. This includes the failure to interpret an IFD
   as a supported image in the case of `*_image` variants.
 
+Compatibility:
+- Changed how tiled TIFF files are detected. The presence of a TileWidth OR
+  TileHeight/TileLength tag now marks an image as tiled. Data is no retrieved
+  from either StripOffsets or TileOffsets with the latter taking precedence.
+  This is closer to the behavior of libtiff.
+
 # Version 0.11.3
 
 Additions:

Cargo.toml

@@ -54,6 +54,7 @@ harness = false
 name = "encode"
 harness = false
 
+
 [[test]]
 name = "decode_libtiffpic"
 path = "tests/decode_libtiffpic.rs"

benches/encode.rs

@@ -4,7 +4,7 @@ extern crate tiff;
 use criterion::{black_box, Criterion, Throughput};
 use std::io::Cursor;
 use tiff::encoder::colortype::RGB32Float;
-use tiff::encoder::{Compression, DeflateLevel, Predictor, TiffEncoder};
+use tiff::encoder::{Compression, Predictor, TiffEncoder};
 
 const WIDTH: u32 = 500;
 const HEIGHT: u32 = 500;
@@ -14,7 +14,7 @@ fn encode_image_f32_float_predictor_deflate(data: &[f32]) {
     TiffEncoder::new(&mut buf)
         .unwrap()
         .with_predictor(Predictor::FloatingPoint)
-        .with_compression(Compression::Deflate(DeflateLevel::Fast))
+        .with_compression(Compression::Deflate(1))
         .write_image::<RGB32Float>(WIDTH, HEIGHT, black_box(data))
         .unwrap();
 }

examples/decode.rs

@@ -1,4 +1,4 @@
-use tiff::decoder::{BufferLayoutPreference, Decoder, DecodingBuffer, DecodingResult};
+use tiff::decoder::{BufferLayoutPreference, Decoder, DecodingSampleBuffer, DecodingSampleSlice};
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let Some(image) = std::env::args_os().nth(1) else {
@@ -10,7 +10,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let io = std::io::BufReader::new(file);
     let mut reader = Decoder::open(io)?;
 
-    let mut data = DecodingResult::I8(vec![]);
+    let mut data = DecodingSampleBuffer::I8(vec![]);
 
     for i in 0u32.. {
         let colortype = reader.colortype()?;
@@ -31,32 +31,32 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
 fn debug_planes(
     index: u32,
-    data: &mut DecodingResult,
+    data: &mut DecodingSampleBuffer,
     layout: &BufferLayoutPreference,
     colortype: &tiff::ColorType,
     (width, height): (u32, u32),
 ) {
     match data {
-        DecodingResult::F16(v) => {
+        DecodingSampleBuffer::F16(v) => {
             let samples = v
                 .iter()
                 .map(|&f| (f64::from(f) * f64::from(u16::MAX)) as u16)
                 .collect::<Vec<_>>();
-            *data = DecodingResult::U16(samples);
+            *data = DecodingSampleBuffer::U16(samples);
         }
-        DecodingResult::F32(v) => {
+        DecodingSampleBuffer::F32(v) => {
             let samples = v
                 .iter()
                 .map(|&f| (f64::from(f) * f64::from(u16::MAX)) as u16)
                 .collect::<Vec<_>>();
-            *data = DecodingResult::U16(samples);
+            *data = DecodingSampleBuffer::U16(samples);
         }
-        DecodingResult::F64(v) => {
+        DecodingSampleBuffer::F64(v) => {
             let samples = v
                 .iter()
                 .map(|&f| (f * f64::from(u16::MAX)) as u16)
                 .collect::<Vec<_>>();
-            *data = DecodingResult::U16(samples);
+            *data = DecodingSampleBuffer::U16(samples);
         }
         _ => {}
     }
@@ -98,24 +98,24 @@ fn debug_planes(
         // them here (e.g. represent 1-bit as `{0, 1}`) but we'd also set `maxval` accordingly and
         // this requires tupltype to be `BLACKANDWHITE` so introducing a bunch of complexity. If
         // you want to do that in your real code, go ahead.
-        DecodingBuffer::U8(buf) => match colortype.bit_depth() {
+        DecodingSampleSlice::U8(buf) => match colortype.bit_depth() {
             8 => u64::from(u8::MAX),
             4 => {
                 fallback_buffer = vec![0; (swidth * sheight) as usize];
                 expand_4bit(buf, swidth, &mut fallback_buffer);
-                *data = DecodingResult::U8(fallback_buffer);
+                *data = DecodingSampleBuffer::U8(fallback_buffer);
                 u64::from(u8::MAX)
             }
             2 => {
                 fallback_buffer = vec![0; (swidth * sheight) as usize];
                 expand_2bit(buf, swidth, &mut fallback_buffer);
-                *data = DecodingResult::U8(fallback_buffer);
+                *data = DecodingSampleBuffer::U8(fallback_buffer);
                 u64::from(u8::MAX)
             }
             1 => {
                 fallback_buffer = vec![0; (swidth * sheight) as usize];
                 expand_1bit(buf, swidth, &mut fallback_buffer);
-                *data = DecodingResult::U8(fallback_buffer);
+                *data = DecodingSampleBuffer::U8(fallback_buffer);
                 u64::from(u8::MAX)
             }
             _ => {
@@ -126,28 +126,30 @@ fn debug_planes(
                 return;
             }
         },
-        DecodingBuffer::U16(_) => u64::from(u16::MAX),
-        DecodingBuffer::U32(_) => u64::from(u32::MAX),
-        DecodingBuffer::U64(_) => u64::MAX,
+        DecodingSampleSlice::U16(_) => u64::from(u16::MAX),
+        DecodingSampleSlice::U32(_) => u64::from(u32::MAX),
+        DecodingSampleSlice::U64(_) => u64::MAX,
         // Eh, this is a good effort I guess.
-        DecodingBuffer::I8(items) => {
+        DecodingSampleSlice::I8(items) => {
             items.iter_mut().for_each(|v| *v = 0.max(*v));
             u64::from(i8::MAX as u8)
         }
-        DecodingBuffer::I16(items) => {
+        DecodingSampleSlice::I16(items) => {
             items.iter_mut().for_each(|v| *v = 0.max(*v));
             u64::from(i16::MAX as u16)
         }
-        DecodingBuffer::I32(items) => {
+        DecodingSampleSlice::I32(items) => {
             items.iter_mut().for_each(|v| *v = 0.max(*v));
             u64::from(i32::MAX as u32)
         }
-        DecodingBuffer::I64(items) => {
+        DecodingSampleSlice::I64(items) => {
             items.iter_mut().for_each(|v| *v = 0.max(*v));
             i64::MAX as u64
         }
         // Not supported by PAM.
-        DecodingBuffer::F16(_) | DecodingBuffer::F32(_) | DecodingBuffer::F64(_) => return,
+        DecodingSampleSlice::F16(_) | DecodingSampleSlice::F32(_) | DecodingSampleSlice::F64(_) => {
+            return
+        }
     };
 
     let byte_len = if layout.planes > 1 {

src/decoder/buffer.rs

@@ -0,0 +1,410 @@
+use half::f16;
+use std::alloc::{Layout, LayoutError};
+
+use crate::{
+    bytecast,
+    decoder::{BufferLayoutPreference, Limits},
+    error::{TiffError, TiffResult, TiffUnsupportedError},
+    tags::{ByteOrder, EndianBytes, SampleFormat},
+};
+
+/// Result of a decoding process
+#[derive(Debug)]
+pub enum DecodingSampleBuffer {
+    /// A vector of unsigned bytes
+    U8(Vec<u8>),
+    /// A vector of unsigned words
+    U16(Vec<u16>),
+    /// A vector of 32 bit unsigned ints
+    U32(Vec<u32>),
+    /// A vector of 64 bit unsigned ints
+    U64(Vec<u64>),
+    /// A vector of 16 bit IEEE floats (held in u16)
+    F16(Vec<f16>),
+    /// A vector of 32 bit IEEE floats
+    F32(Vec<f32>),
+    /// A vector of 64 bit IEEE floats
+    F64(Vec<f64>),
+    /// A vector of 8 bit signed ints
+    I8(Vec<i8>),
+    /// A vector of 16 bit signed ints
+    I16(Vec<i16>),
+    /// A vector of 32 bit signed ints
+    I32(Vec<i32>),
+    /// A vector of 64 bit signed ints
+    I64(Vec<i64>),
+}
+
+impl DecodingSampleBuffer {
+    /// Reallocate the buffer to decode all planes of the indicated layout.
+    pub fn resize_to(
+        &mut self,
+        buffer: &BufferLayoutPreference,
+        limits: &Limits,
+    ) -> Result<(), TiffError> {
+        let sample_type = buffer.sample_type.ok_or(TiffError::UnsupportedError(
+            TiffUnsupportedError::UnknownInterpretation,
+        ))?;
+
+        let extent = sample_type.extent_for_bytes(buffer.complete_len);
+        self.resize_to_extent(extent, limits)
+    }
+
+    pub(crate) fn resize_to_extent(
+        &mut self,
+        extent: DecodingExtent,
+        limits: &Limits,
+    ) -> Result<(), TiffError> {
+        // FIXME: we *can* reuse the allocation sometimes.
+        *self = extent.to_result_buffer(limits)?;
+        Ok(())
+    }
+
+    fn new<T: Default + Copy>(
+        size: usize,
+        limits: &Limits,
+        from_fn: fn(Vec<T>) -> Self,
+    ) -> TiffResult<DecodingSampleBuffer> {
+        if size > limits.decoding_buffer_size / core::mem::size_of::<T>() {
+            Err(TiffError::LimitsExceeded)
+        } else {
+            Ok(from_fn(vec![T::default(); size]))
+        }
+    }
+
+    fn new_u8(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::U8)
+    }
+
+    fn new_u16(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::U16)
+    }
+
+    fn new_u32(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::U32)
+    }
+
+    fn new_u64(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::U64)
+    }
+
+    fn new_f32(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::F32)
+    }
+
+    fn new_f64(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::F64)
+    }
+
+    fn new_f16(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::F16)
+    }
+
+    fn new_i8(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::I8)
+    }
+
+    fn new_i16(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::I16)
+    }
+
+    fn new_i32(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::I32)
+    }
+
+    fn new_i64(size: usize, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        Self::new(size, limits, DecodingSampleBuffer::I64)
+    }
+
+    /// Get a view of this buffer starting from the nth _sample_ of the current type.
+    pub fn as_buffer(&mut self, start: usize) -> DecodingSampleSlice<'_> {
+        match *self {
+            DecodingSampleBuffer::U8(ref mut buf) => DecodingSampleSlice::U8(&mut buf[start..]),
+            DecodingSampleBuffer::U16(ref mut buf) => DecodingSampleSlice::U16(&mut buf[start..]),
+            DecodingSampleBuffer::U32(ref mut buf) => DecodingSampleSlice::U32(&mut buf[start..]),
+            DecodingSampleBuffer::U64(ref mut buf) => DecodingSampleSlice::U64(&mut buf[start..]),
+            DecodingSampleBuffer::F16(ref mut buf) => DecodingSampleSlice::F16(&mut buf[start..]),
+            DecodingSampleBuffer::F32(ref mut buf) => DecodingSampleSlice::F32(&mut buf[start..]),
+            DecodingSampleBuffer::F64(ref mut buf) => DecodingSampleSlice::F64(&mut buf[start..]),
+            DecodingSampleBuffer::I8(ref mut buf) => DecodingSampleSlice::I8(&mut buf[start..]),
+            DecodingSampleBuffer::I16(ref mut buf) => DecodingSampleSlice::I16(&mut buf[start..]),
+            DecodingSampleBuffer::I32(ref mut buf) => DecodingSampleSlice::I32(&mut buf[start..]),
+            DecodingSampleBuffer::I64(ref mut buf) => DecodingSampleSlice::I64(&mut buf[start..]),
+        }
+    }
+
+    pub fn sample_type(&self) -> DecodingSampleType {
+        match *self {
+            DecodingSampleBuffer::U8(_) => DecodingSampleType::U8,
+            DecodingSampleBuffer::U16(_) => DecodingSampleType::U16,
+            DecodingSampleBuffer::U32(_) => DecodingSampleType::U32,
+            DecodingSampleBuffer::U64(_) => DecodingSampleType::U64,
+            DecodingSampleBuffer::F16(_) => DecodingSampleType::F16,
+            DecodingSampleBuffer::F32(_) => DecodingSampleType::F32,
+            DecodingSampleBuffer::F64(_) => DecodingSampleType::F64,
+            DecodingSampleBuffer::I8(_) => DecodingSampleType::I8,
+            DecodingSampleBuffer::I16(_) => DecodingSampleType::I16,
+            DecodingSampleBuffer::I32(_) => DecodingSampleType::I32,
+            DecodingSampleBuffer::I64(_) => DecodingSampleType::I64,
+        }
+    }
+
+    /// Change the endianess of buffered data.
+    ///
+    /// This utility may be used to prepare a buffer for consumption by methods taking raw bytes or
+    /// after filling the buffer with raw bytes.
+    ///
+    /// After this, interpreting the buffer on the host may no longer produce any reasonable
+    /// results. For instance, floats in the wrong byte order may produce a `NaN` with varying
+    /// payloads. Despite unexpected result however, this operation is always sound.
+    pub fn convert_endian(&mut self, from: ByteOrder, to: ByteOrder) {
+        self.as_buffer(0).convert_endian(from, to)
+    }
+}
+
+// A buffer for image decoding
+pub enum DecodingSampleSlice<'a> {
+    /// A slice of unsigned bytes
+    U8(&'a mut [u8]),
+    /// A slice of unsigned words
+    U16(&'a mut [u16]),
+    /// A slice of 32 bit unsigned ints
+    U32(&'a mut [u32]),
+    /// A slice of 64 bit unsigned ints
+    U64(&'a mut [u64]),
+    /// A slice of 16 bit IEEE floats
+    F16(&'a mut [f16]),
+    /// A slice of 32 bit IEEE floats
+    F32(&'a mut [f32]),
+    /// A slice of 64 bit IEEE floats
+    F64(&'a mut [f64]),
+    /// A slice of 8 bits signed ints
+    I8(&'a mut [i8]),
+    /// A slice of 16 bits signed ints
+    I16(&'a mut [i16]),
+    /// A slice of 32 bits signed ints
+    I32(&'a mut [i32]),
+    /// A slice of 64 bits signed ints
+    I64(&'a mut [i64]),
+}
+
+impl<'a> DecodingSampleSlice<'a> {
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            DecodingSampleSlice::U8(buf) => buf,
+            DecodingSampleSlice::I8(buf) => bytecast::i8_as_ne_bytes(buf),
+            DecodingSampleSlice::U16(buf) => bytecast::u16_as_ne_bytes(buf),
+            DecodingSampleSlice::I16(buf) => bytecast::i16_as_ne_bytes(buf),
+            DecodingSampleSlice::U32(buf) => bytecast::u32_as_ne_bytes(buf),
+            DecodingSampleSlice::I32(buf) => bytecast::i32_as_ne_bytes(buf),
+            DecodingSampleSlice::U64(buf) => bytecast::u64_as_ne_bytes(buf),
+            DecodingSampleSlice::I64(buf) => bytecast::i64_as_ne_bytes(buf),
+            DecodingSampleSlice::F16(buf) => bytecast::f16_as_ne_bytes(buf),
+            DecodingSampleSlice::F32(buf) => bytecast::f32_as_ne_bytes(buf),
+            DecodingSampleSlice::F64(buf) => bytecast::f64_as_ne_bytes(buf),
+        }
+    }
+
+    pub fn as_bytes_mut(&mut self) -> &mut [u8] {
+        match self {
+            DecodingSampleSlice::U8(buf) => buf,
+            DecodingSampleSlice::I8(buf) => bytecast::i8_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::U16(buf) => bytecast::u16_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::I16(buf) => bytecast::i16_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::U32(buf) => bytecast::u32_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::I32(buf) => bytecast::i32_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::U64(buf) => bytecast::u64_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::I64(buf) => bytecast::i64_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::F16(buf) => bytecast::f16_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::F32(buf) => bytecast::f32_as_ne_mut_bytes(buf),
+            DecodingSampleSlice::F64(buf) => bytecast::f64_as_ne_mut_bytes(buf),
+        }
+    }
+
+    pub fn reborrow(&mut self) -> DecodingSampleSlice<'_> {
+        match self {
+            DecodingSampleSlice::U8(items) => DecodingSampleSlice::U8(items),
+            DecodingSampleSlice::I8(items) => DecodingSampleSlice::I8(items),
+            DecodingSampleSlice::U16(items) => DecodingSampleSlice::U16(items),
+            DecodingSampleSlice::I16(items) => DecodingSampleSlice::I16(items),
+            DecodingSampleSlice::U32(items) => DecodingSampleSlice::U32(items),
+            DecodingSampleSlice::I32(items) => DecodingSampleSlice::I32(items),
+            DecodingSampleSlice::U64(items) => DecodingSampleSlice::U64(items),
+            DecodingSampleSlice::I64(items) => DecodingSampleSlice::I64(items),
+            DecodingSampleSlice::F16(items) => DecodingSampleSlice::F16(items),
+            DecodingSampleSlice::F32(items) => DecodingSampleSlice::F32(items),
+            DecodingSampleSlice::F64(items) => DecodingSampleSlice::F64(items),
+        }
+    }
+
+    pub fn sample_type(&self) -> DecodingSampleType {
+        match *self {
+            DecodingSampleSlice::U8(_) => DecodingSampleType::U8,
+            DecodingSampleSlice::U16(_) => DecodingSampleType::U16,
+            DecodingSampleSlice::U32(_) => DecodingSampleType::U32,
+            DecodingSampleSlice::U64(_) => DecodingSampleType::U64,
+            DecodingSampleSlice::F16(_) => DecodingSampleType::F16,
+            DecodingSampleSlice::F32(_) => DecodingSampleType::F32,
+            DecodingSampleSlice::F64(_) => DecodingSampleType::F64,
+            DecodingSampleSlice::I8(_) => DecodingSampleType::I8,
+            DecodingSampleSlice::I16(_) => DecodingSampleType::I16,
+            DecodingSampleSlice::I32(_) => DecodingSampleType::I32,
+            DecodingSampleSlice::I64(_) => DecodingSampleType::I64,
+        }
+    }
+
+    /// Change the endianess of referenced data.
+    ///
+    /// This utility may be used to prepare a buffer for consumption by methods taking raw bytes or
+    /// after filling the buffer with raw bytes.
+    ///
+    /// After this, interpreting the buffer on the host may no longer produce any reasonable
+    /// results. For instance, floats in the wrong byte order may produce a `NaN` with varying
+    /// payloads. Despite unexpected result however, this operation is always sound.
+    pub fn convert_endian(&mut self, from: ByteOrder, to: ByteOrder) {
+        let byte_unit = self.sample_type().endian_bytes();
+        from.convert_endian_bytes(byte_unit, self.as_bytes_mut(), to);
+    }
+
+    pub fn byte_len(&self) -> usize {
+        self.as_bytes().len()
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum DecodingSampleType {
+    U8,
+    U16,
+    U32,
+    U64,
+    F16,
+    F32,
+    F64,
+    I8,
+    I16,
+    I32,
+    I64,
+}
+
+impl DecodingSampleType {
+    pub fn sample_format(self) -> SampleFormat {
+        match self {
+            DecodingSampleType::U8 => SampleFormat::Uint,
+            DecodingSampleType::U16 => SampleFormat::Uint,
+            DecodingSampleType::U32 => SampleFormat::Uint,
+            DecodingSampleType::U64 => SampleFormat::Uint,
+            DecodingSampleType::F16 => SampleFormat::IEEEFP,
+            DecodingSampleType::F32 => SampleFormat::IEEEFP,
+            DecodingSampleType::F64 => SampleFormat::IEEEFP,
+            DecodingSampleType::I8 => SampleFormat::Int,
+            DecodingSampleType::I16 => SampleFormat::Int,
+            DecodingSampleType::I32 => SampleFormat::Int,
+            DecodingSampleType::I64 => SampleFormat::Int,
+        }
+    }
+
+    pub(crate) fn extent_for_bytes(self, bytes: usize) -> DecodingExtent {
+        match self {
+            DecodingSampleType::U8 => DecodingExtent::U8(bytes),
+            DecodingSampleType::U16 => DecodingExtent::U16(bytes.div_ceil(2)),
+            DecodingSampleType::U32 => DecodingExtent::U32(bytes.div_ceil(4)),
+            DecodingSampleType::U64 => DecodingExtent::U64(bytes.div_ceil(8)),
+            DecodingSampleType::I8 => DecodingExtent::I8(bytes),
+            DecodingSampleType::I16 => DecodingExtent::I16(bytes.div_ceil(2)),
+            DecodingSampleType::I32 => DecodingExtent::I32(bytes.div_ceil(4)),
+            DecodingSampleType::I64 => DecodingExtent::I64(bytes.div_ceil(8)),
+            DecodingSampleType::F16 => DecodingExtent::F16(bytes.div_ceil(2)),
+            DecodingSampleType::F32 => DecodingExtent::F32(bytes.div_ceil(4)),
+            DecodingSampleType::F64 => DecodingExtent::F64(bytes.div_ceil(8)),
+        }
+    }
+
+    fn endian_bytes(self) -> EndianBytes {
+        use EndianBytes::*;
+
+        match self {
+            DecodingSampleType::U8 => One,
+            DecodingSampleType::U16 => Two,
+            DecodingSampleType::U32 => Four,
+            DecodingSampleType::U64 => Eight,
+            DecodingSampleType::F16 => Two,
+            DecodingSampleType::F32 => Four,
+            DecodingSampleType::F64 => Eight,
+            DecodingSampleType::I8 => One,
+            DecodingSampleType::I16 => Two,
+            DecodingSampleType::I32 => Four,
+            DecodingSampleType::I64 => Eight,
+        }
+    }
+}
+
+/// The count and matching discriminant for a `DecodingBuffer`.
+#[derive(Clone)]
+pub(crate) enum DecodingExtent {
+    U8(usize),
+    U16(usize),
+    U32(usize),
+    U64(usize),
+    F16(usize),
+    F32(usize),
+    F64(usize),
+    I8(usize),
+    I16(usize),
+    I32(usize),
+    I64(usize),
+}
+
+impl DecodingExtent {
+    pub(crate) fn to_result_buffer(&self, limits: &Limits) -> TiffResult<DecodingSampleBuffer> {
+        match *self {
+            DecodingExtent::U8(count) => DecodingSampleBuffer::new_u8(count, limits),
+            DecodingExtent::U16(count) => DecodingSampleBuffer::new_u16(count, limits),
+            DecodingExtent::U32(count) => DecodingSampleBuffer::new_u32(count, limits),
+            DecodingExtent::U64(count) => DecodingSampleBuffer::new_u64(count, limits),
+            DecodingExtent::F16(count) => DecodingSampleBuffer::new_f16(count, limits),
+            DecodingExtent::F32(count) => DecodingSampleBuffer::new_f32(count, limits),
+            DecodingExtent::F64(count) => DecodingSampleBuffer::new_f64(count, limits),
+            DecodingExtent::I8(count) => DecodingSampleBuffer::new_i8(count, limits),
+            DecodingExtent::I16(count) => DecodingSampleBuffer::new_i16(count, limits),
+            DecodingExtent::I32(count) => DecodingSampleBuffer::new_i32(count, limits),
+            DecodingExtent::I64(count) => DecodingSampleBuffer::new_i64(count, limits),
+        }
+    }
+
+    pub(crate) fn preferred_layout(self) -> TiffResult<Layout> {
+        fn overflow(_: LayoutError) -> TiffError {
+            TiffError::LimitsExceeded
+        }
+
+        match self {
+            DecodingExtent::U8(count) => Layout::array::<u8>(count),
+            DecodingExtent::U16(count) => Layout::array::<u16>(count),
+            DecodingExtent::U32(count) => Layout::array::<u32>(count),
+            DecodingExtent::U64(count) => Layout::array::<u64>(count),
+            DecodingExtent::F16(count) => Layout::array::<f16>(count),
+            DecodingExtent::F32(count) => Layout::array::<f32>(count),
+            DecodingExtent::F64(count) => Layout::array::<f64>(count),
+            DecodingExtent::I8(count) => Layout::array::<i8>(count),
+            DecodingExtent::I16(count) => Layout::array::<i16>(count),
+            DecodingExtent::I32(count) => Layout::array::<i32>(count),
+            DecodingExtent::I64(count) => Layout::array::<i64>(count),
+        }
+        .map_err(overflow)
+    }
+
+    pub(crate) fn sample_type(&self) -> DecodingSampleType {
+        match *self {
+            DecodingExtent::U8(_) => DecodingSampleType::U8,
+            DecodingExtent::U16(_) => DecodingSampleType::U16,
+            DecodingExtent::U32(_) => DecodingSampleType::U32,
+            DecodingExtent::U64(_) => DecodingSampleType::U64,
+            DecodingExtent::F16(_) => DecodingSampleType::F16,
+            DecodingExtent::F32(_) => DecodingSampleType::F32,
+            DecodingExtent::F64(_) => DecodingSampleType::F64,
+            DecodingExtent::I8(_) => DecodingSampleType::I8,
+            DecodingExtent::I16(_) => DecodingSampleType::I16,
+            DecodingExtent::I32(_) => DecodingSampleType::I32,
+            DecodingExtent::I64(_) => DecodingSampleType::I64,
+        }
+    }
+}

src/decoder/cycles.rs

@@ -11,7 +11,7 @@ use std::collections::HashMap;
 ///
 /// Since we only consider one child, we run union find to assign each pointer to a known chain.
 /// Then, when we insert a new edge we check if they belong to the same component.
-#[derive(Default, Debug)]
+#[derive(Clone, Default, Debug)]
 pub struct IfdCycles {
     /// The root of each component union.
     component_union: HashMap<ComponentId, ComponentId>,

src/decoder/entry_reader.rs

@@ -0,0 +1,362 @@
+use std::io::{self, Cursor, Read, Seek};
+
+use crate::{
+    decoder::{ifd::Entry, stream::EndianReader, ValueReader},
+    tags::{ByteOrder, IfdPointer, Type},
+    TiffResult,
+};
+
+pub struct EntryBytesReader<'lt, R> {
+    inner: &'lt mut EndianReader<R>,
+    variant: Variant,
+}
+
+const OFFSET_BUFFER_LEN: usize = 8;
+
+enum Variant {
+    Immediate {
+        /// An in-value reader if the offset field contains the data. Note that we rotate it to the
+        /// back of this buffer, not the front, so that `Cursor` already contains the right end.
+        /// We do not let you seek back beyond our start.
+        data: Cursor<[u8; OFFSET_BUFFER_LEN]>,
+        value_bytes: u8,
+    },
+    InFile {
+        // the length relative to the base so we can seek relative without querying the position.
+        value_bytes: u64,
+        remainder: u64,
+        base: u64,
+    },
+}
+
+impl<'lt, R> EntryBytesReader<'lt, R> {
+    pub(super) fn from_entry(inner: &'lt mut ValueReader<R>, entry: Entry) -> TiffResult<Self>
+    where
+        R: Read + Seek,
+    {
+        let offset: [_; OFFSET_BUFFER_LEN] = *entry.offset_raw();
+        let limit = if inner.bigtiff { 8 } else { 4 };
+        assert!(limit as usize <= OFFSET_BUFFER_LEN);
+
+        let value_bytes = entry.field_type().value_bytes(entry.count())?;
+
+        if value_bytes <= limit {
+            // We move the data to the back of the array whereas it is in the front right now.
+            let mut value = offset;
+            value.rotate_left(value_bytes as usize);
+            let mut cursor = Cursor::new(value);
+            cursor.set_position(OFFSET_BUFFER_LEN as u64 - value_bytes);
+
+            Ok(EntryBytesReader {
+                inner: &mut inner.reader,
+                variant: Variant::Immediate {
+                    data: cursor,
+                    value_bytes: value_bytes as u8,
+                },
+            })
+        } else {
+            // remainder > limit >= 0 so this is an unreachable panic.
+            let pointer = if inner.bigtiff {
+                let mut offset = offset;
+
+                inner
+                    .reader
+                    .byte_order
+                    .convert(Type::IFD8, &mut offset[..], ByteOrder::native());
+
+                IfdPointer(u64::from_ne_bytes(offset))
+            } else {
+                let mut offset = *offset.first_chunk::<4>().unwrap();
+
+                inner
+                    .reader
+                    .byte_order
+                    .convert(Type::IFD, &mut offset[..], ByteOrder::native());
+
+                let offset = u32::from_ne_bytes(offset);
+                IfdPointer(u64::from(offset))
+            };
+
+            inner.reader.goto_offset(pointer.0)?;
+
+            Ok(EntryBytesReader {
+                inner: &mut inner.reader,
+                variant: Variant::InFile {
+                    value_bytes,
+                    remainder: value_bytes,
+                    base: pointer.0,
+                },
+            })
+        }
+    }
+}
+
+impl<R: Read> Read for EntryBytesReader<'_, R> {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        match &mut self.variant {
+            Variant::Immediate { data, .. } => data.read(buf),
+            Variant::InFile { remainder, .. } => {
+                let bound = usize::try_from(*remainder).unwrap_or(usize::MAX);
+                let avail = buf.len().min(bound);
+                let read = self.inner.inner().read(&mut buf[..avail])?;
+
+                // On a well-behaved `Read`: read <= avail <= bound <=(mathematical) remainder
+                let consume = read as u64;
+                *remainder -= consume;
+                Ok(read)
+            }
+        }
+    }
+
+    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
+        match &mut self.variant {
+            Variant::Immediate { data, .. } => data.read_exact(buf),
+            Variant::InFile { remainder, .. } => {
+                let bound = usize::try_from(*remainder).unwrap_or(usize::MAX);
+
+                // Fail early if we would be sure to over-read.
+                if buf.len() > bound {
+                    return Err(io::Error::new(
+                        io::ErrorKind::UnexpectedEof,
+                        "Tiff value shorter than the requested buffer size",
+                    ));
+                }
+
+                // since buf.len() <= bound <=(mathematical) remainder
+                let consume = buf.len() as u64;
+                self.inner.inner().read_exact(buf)?;
+                *remainder -= consume;
+
+                Ok(())
+            }
+        }
+    }
+}
+
+impl<R: Read + Seek> Seek for EntryBytesReader<'_, R> {
+    fn seek(&mut self, offset: io::SeekFrom) -> io::Result<u64> {
+        let (value_bytes, remainder) = match &self.variant {
+            Variant::Immediate { data, value_bytes } => {
+                let remainder = data.get_ref().len() as u64 - data.position();
+                (*value_bytes as u64, remainder)
+            }
+            &Variant::InFile {
+                value_bytes,
+                remainder,
+                base: _,
+            } => (value_bytes, remainder),
+        };
+
+        // Normalize to an offset from the start
+        let offset_from_start = match offset {
+            io::SeekFrom::Start(n) => Some(n),
+            io::SeekFrom::Current(n) => {
+                let front = value_bytes - remainder;
+                front.checked_add_signed(n)
+            }
+            io::SeekFrom::End(n) => value_bytes.checked_add_signed(n),
+        };
+
+        let Some((offset, remainder)) = offset_from_start.and_then(|n| {
+            let remainder = value_bytes.checked_sub(n)?;
+            Some((n, remainder))
+        }) else {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "seek out of bounds of entry value",
+            ));
+        };
+
+        match &mut self.variant {
+            Variant::Immediate { data, .. } => {
+                let start = OFFSET_BUFFER_LEN as u64 - value_bytes;
+                data.set_position(start + offset);
+                Ok(offset)
+            }
+            &mut Variant::InFile { base, .. } => {
+                // We checked this against overflow on construction. Ignore the offset we get.
+                self.inner
+                    .inner()
+                    .seek(io::SeekFrom::Start(base + offset))?;
+
+                self.variant = Variant::InFile {
+                    value_bytes,
+                    remainder,
+                    base,
+                };
+
+                Ok(offset)
+            }
+        }
+    }
+
+    fn stream_position(&mut self) -> io::Result<u64> {
+        Ok(match &self.variant {
+            Variant::Immediate { data, value_bytes } => {
+                // Recall the value is at the end of the buffer.
+                let from_end = OFFSET_BUFFER_LEN as u64 - data.position();
+                u64::from(*value_bytes) - from_end
+            }
+            // Note: we might think about using the inner `stream_position` here. However that
+            // exposes something interesting: If the internal stream is modified concurrently from
+            // another instance (e.g. a shared `File`) then we may lose track of it anyways.
+            // Especially the `Read` implementation is not bounded on `Seek` so it could not
+            // acquire the position. And it should not since that is just a different form of race
+            // where we risk the position being modified by a different thread just as well.
+            //
+            // So in the interest of least surprise we just assume that we can track the position
+            // accurately here and that the inner reader uses for instance `read_at` consistently.
+            // We own the value (or mutable reference) it after all.
+            //
+            // Also this one MUST be compatible with `seek(SeekFrom::Current(0))` as per trait
+            // defintion—so at least keep those consistent if changing anything.
+            &Variant::InFile {
+                remainder,
+                value_bytes,
+                ..
+            } => value_bytes - remainder,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{decoder::Decoder, encoder, tags};
+    use std::io::{Read as _, Seek as _, SeekFrom};
+
+    #[test]
+    fn can_seek_tag_bytes() -> Result<(), crate::error::TiffError> {
+        let file = std::fs::File::open(concat!(
+            env!("CARGO_MANIFEST_DIR"),
+            "/tests/images/int8_rgb.tif"
+        ))
+        .unwrap();
+
+        let mut decoder = Decoder::open(file).unwrap();
+        decoder.next_directory().unwrap();
+
+        let mut buffer = crate::tags::ValueBuffer::default();
+
+        decoder
+            .current_ifd()
+            .find_tag_buf(tags::Tag::StripByteCounts, &mut buffer)
+            .expect("some strip byte count is present");
+
+        let bytes_of_value = buffer.as_bytes().len() as u64;
+
+        let mut reader = decoder
+            .read_tag(tags::Tag::StripByteCounts)?
+            .expect("some strip byte count is present");
+
+        let mut data = vec![];
+        reader.read_to_end(&mut data)?;
+
+        // `ValueBuffer` also stores its data in the file endianess until converted.
+        assert_eq!(reader.stream_position()?, bytes_of_value);
+        assert_eq!(buffer.as_bytes(), data);
+
+        reader.seek(SeekFrom::Start(0))?;
+        assert_eq!(reader.stream_position()?, 0);
+        reader.read_to_end(&mut data)?;
+        assert_eq!(reader.stream_position()?, bytes_of_value);
+
+        let (first, second) = data.split_at(bytes_of_value as usize);
+        assert_eq!(first, second);
+
+        Ok(())
+    }
+
+    #[test]
+    #[allow(clippy::seek_from_current)] // We want to test that functionality.
+    fn seek_from_end() -> Result<(), crate::error::TiffError> {
+        const ARTIST: &str = "99 little bugs in the code";
+
+        let data = {
+            let mut data = std::io::Cursor::new(vec![]);
+            let mut encoder = encoder::TiffEncoder::new(&mut data)?;
+
+            let mut dir = encoder.image_directory()?;
+            dir.write_tag(tags::Tag::Artist, ARTIST)?;
+            dir.finish()?;
+
+            data.into_inner()
+        };
+
+        let file = std::io::Cursor::new(data);
+        let mut decoder = Decoder::open(file).unwrap();
+        decoder.next_directory().unwrap();
+
+        let mut reader = decoder
+            .read_tag(tags::Tag::Artist)?
+            .expect("the artist is present?");
+
+        let mut value = vec![];
+        reader.read_to_end(&mut value)?;
+
+        let (&nul, value) = value.split_last().unwrap();
+        assert_eq!(value, ARTIST.as_bytes());
+        assert_eq!(nul, b'\0');
+
+        assert_eq!(reader.seek(SeekFrom::End(0))?, ARTIST.len() as u64 + 1);
+        assert!(reader.seek(SeekFrom::End(1)).is_err());
+        assert_eq!(reader.stream_position()?, ARTIST.len() as u64 + 1);
+
+        // Check relative seeks by comparing against the "code"
+        let code_offset = reader.seek(SeekFrom::End(-5))?;
+        let mut is_code = [0u8; 4];
+        reader.read_exact(&mut is_code)?;
+        assert_eq!(is_code, *value.last_chunk::<4>().unwrap());
+
+        assert_eq!(reader.seek(SeekFrom::Start(0))?, 0);
+        assert_eq!(reader.stream_position()?, 0);
+        assert_eq!(reader.seek(SeekFrom::Current(0))?, 0);
+        assert_eq!(reader.stream_position()?, 0);
+        assert!(reader.seek(SeekFrom::Current(-1)).is_err());
+        assert_eq!(reader.stream_position()?, 0);
+
+        reader.seek(SeekFrom::Start(code_offset))?;
+        reader.read_exact(&mut is_code)?;
+        assert_eq!(reader.stream_position()?, ARTIST.len() as u64);
+        assert_eq!(is_code, *value.last_chunk::<4>().unwrap());
+
+        Ok(())
+    }
+
+    /// Check that the reader from an `offset` field also works.
+    #[test]
+    fn read_from_offset() -> Result<(), crate::error::TiffError> {
+        let data = {
+            let mut data = std::io::Cursor::new(vec![]);
+            let mut encoder = encoder::TiffEncoder::new(&mut data)?;
+
+            let mut dir = encoder.image_directory()?;
+            dir.write_tag(
+                tags::Tag::PlanarConfiguration,
+                tags::PlanarConfiguration::Planar,
+            )?;
+            dir.finish()?;
+
+            data.into_inner()
+        };
+
+        let file = std::io::Cursor::new(data);
+        let mut decoder = Decoder::open(file).unwrap();
+        decoder.next_directory().unwrap();
+        let bo = decoder.byte_order();
+
+        let mut reader = decoder
+            .read_tag(tags::Tag::PlanarConfiguration)?
+            .expect("some artist is present");
+
+        let mut buf = [0; 2];
+        reader.read_exact(&mut buf)?;
+
+        bo.convert(tags::Type::SHORT, &mut buf, tags::ByteOrder::BigEndian);
+        assert_eq!(buf, [0, 2]);
+
+        // Check relative seeks, this item is only two bytes long.
+        assert!(reader.seek(SeekFrom::End(-3)).is_err());
+
+        Ok(())
+    }
+}

src/decoder/ifd.rs

@@ -393,7 +393,7 @@ impl Entry {
         self.count
     }
 
-    pub(crate) fn offset(&self) -> &[u8] {
+    pub(crate) fn offset_raw(&self) -> &[u8; 8] {
         &self.offset
     }
 

src/decoder/image.rs

@@ -85,6 +85,11 @@ pub(crate) struct Image {
     pub chunk_offsets: Vec<u64>,
     pub chunk_bytes: Vec<u64>,
     pub chroma_subsampling: (u16, u16),
+    /// FillOrder: 1 = MSB-to-LSB (default), 2 = LSB-to-MSB (common in fax images)
+    pub fill_order: u16,
+    /// The color map (palette) for `PhotometricInterpretation::RGBPalette`.
+    /// Contains `3 * 2^BitsPerSample` u16 entries: R values, then G values, then B values.
+    pub color_map: Option<Vec<u16>>,
     /// Will decompression yield host-endian samples?
     ///
     /// Standard compression algorithms run on pure bytes, taking the sample slice as it would be
@@ -132,6 +137,10 @@ pub(crate) struct ReadoutLayout {
 
     /// Bits per sample in the encoded data.
     pub tiff_bits_per_sample: u8,
+    /// Bits per sample in the output buffer, promoted to a standard width.
+    /// For sub-byte depths (1-8): same as tiff_bits_per_sample.
+    /// For 9-16: 16. For 17-32: 32. For 33-64: 64.
+    pub output_bits_per_sample: u8,
     /// Number of samples in the encoded data.
     pub tiff_samples: u16,
     /// Dimensions of the underlying rectangular chunks (tile or strips).
@@ -146,30 +155,6 @@ pub(crate) struct ReadoutLayout {
 }
 
 impl Image {
-    pub(crate) fn no_image() -> Image {
-        Image {
-            width: 0,
-            height: 0,
-            bits_per_sample: 1,
-            samples: 1,
-            extra_samples: vec![],
-            photometric_samples: 1,
-            sample_format: SampleFormat::Uint,
-            photometric_interpretation: PhotometricInterpretation::BlackIsZero,
-            compression_method: CompressionMethod::None,
-            jpeg_tables: None,
-            predictor: Predictor::None,
-            chunk_type: ChunkType::Strip,
-            planar_config: PlanarConfiguration::Chunky,
-            strip_decoder: None,
-            tile_attributes: None,
-            chunk_offsets: Vec::new(),
-            chunk_bytes: Vec::new(),
-            chroma_subsampling: (2, 2),
-            decompression_to_host_endian: false,
-        }
-    }
-
     pub fn from_reader<R: Read + Seek>(
         decoder: &mut ValueReader<R>,
         ifd: &Directory,
@@ -325,118 +310,125 @@ impl Image {
             (2, 2)
         };
 
+        let fill_order = tag_reader
+            .find_tag(Tag::FillOrder)?
+            .map(Value::into_u16)
+            .transpose()?
+            .unwrap_or(1);
+
         let planes = match planar_config {
             PlanarConfiguration::Chunky => 1,
             PlanarConfiguration::Planar => samples,
         };
 
+        // Note: Not strictly according to specification. The specification says that tiled images
+        // must have their data encoded in `TileByteCounts` and `TileOffsets`. But `libtiff`
+        // processes tags one-by-one and with *either* of these it will set the flag for the image
+        // being tiled. Also it will just use whatever offsets are available. (I believe also using
+        // the first of the two tag pairs that's available—remember tags are encoded ascending).
+        let is_tiled = ifd.contains(Tag::TileWidth) || ifd.contains(Tag::TileLength);
+        let has_strips = ifd.contains(Tag::StripByteCounts) && ifd.contains(Tag::StripOffsets);
+        let has_tiles = ifd.contains(Tag::TileByteCounts) && ifd.contains(Tag::TileOffsets);
+
         let chunk_type;
         let chunk_offsets;
         let chunk_bytes;
         let strip_decoder;
         let tile_attributes;
-        match (
-            ifd.contains(Tag::StripByteCounts),
-            ifd.contains(Tag::StripOffsets),
-            ifd.contains(Tag::TileByteCounts),
-            ifd.contains(Tag::TileOffsets),
-        ) {
-            (true, true, false, false) => {
-                chunk_type = ChunkType::Strip;
 
-                chunk_offsets = tag_reader
-                    .find_tag(Tag::StripOffsets)?
-                    .unwrap()
-                    .into_u64_vec()?;
-                chunk_bytes = tag_reader
-                    .find_tag(Tag::StripByteCounts)?
-                    .unwrap()
-                    .into_u64_vec()?;
-                let rows_per_strip = tag_reader
-                    .find_tag(Tag::RowsPerStrip)?
-                    .map(Value::into_u32)
-                    .transpose()?
-                    .unwrap_or(height);
-                strip_decoder = Some(StripDecodeState { rows_per_strip });
-                tile_attributes = None;
+        if !is_tiled && has_strips {
+            chunk_type = ChunkType::Strip;
 
-                if chunk_offsets.len() != chunk_bytes.len() {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::InconsistentSizesEncountered,
-                    ));
-                }
+            chunk_offsets = tag_reader
+                .find_tag(Tag::StripOffsets)?
+                .unwrap()
+                .into_u64_vec()?;
+            chunk_bytes = tag_reader
+                .find_tag(Tag::StripByteCounts)?
+                .unwrap()
+                .into_u64_vec()?;
+            let rows_per_strip = tag_reader
+                .find_tag(Tag::RowsPerStrip)?
+                .map(Value::into_u32)
+                .transpose()?
+                .unwrap_or(height);
+            strip_decoder = Some(StripDecodeState { rows_per_strip });
+            tile_attributes = None;
 
-                if rows_per_strip == 0 {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::InconsistentSizesEncountered,
-                    ));
-                }
-
-                if u32::try_from(chunk_offsets.len())?
-                    != height.div_ceil(rows_per_strip) * planes as u32
-                {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::IncorrectChunkCount {
-                            expected: height.div_ceil(rows_per_strip) * planes as u32,
-                            found: chunk_offsets.len() as u32,
-                        },
-                    ));
-                }
-            }
-            (false, false, true, true) => {
-                chunk_type = ChunkType::Tile;
-
-                let tile_width =
-                    usize::try_from(tag_reader.require_tag(Tag::TileWidth)?.into_u32()?)?;
-                let tile_length =
-                    usize::try_from(tag_reader.require_tag(Tag::TileLength)?.into_u32()?)?;
-
-                if tile_width == 0 {
-                    return Err(TiffFormatError::InvalidTagValueType(Tag::TileWidth).into());
-                } else if tile_length == 0 {
-                    return Err(TiffFormatError::InvalidTagValueType(Tag::TileLength).into());
-                }
-
-                strip_decoder = None;
-                tile_attributes = Some(TileAttributes {
-                    image_width: usize::try_from(width)?,
-                    image_height: usize::try_from(height)?,
-                    tile_width,
-                    tile_length,
-                });
-                chunk_offsets = tag_reader
-                    .find_tag(Tag::TileOffsets)?
-                    .unwrap()
-                    .into_u64_vec()?;
-                chunk_bytes = tag_reader
-                    .find_tag(Tag::TileByteCounts)?
-                    .unwrap()
-                    .into_u64_vec()?;
-
-                let tile = tile_attributes.as_ref().unwrap();
-
-                if chunk_offsets.len() != chunk_bytes.len() {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::InconsistentSizesEncountered,
-                    ));
-                }
-
-                if chunk_offsets.len() != tile.tiles_down() * tile.tiles_across() * planes as usize
-                {
-                    return Err(TiffError::FormatError(
-                        TiffFormatError::IncorrectChunkCount {
-                            expected: (tile.tiles_down() * tile.tiles_across() * planes as usize)
-                                as u32,
-                            found: chunk_offsets.len() as u32,
-                        },
-                    ));
-                }
-            }
-            (_, _, _, _) => {
+            if chunk_offsets.len() != chunk_bytes.len() {
                 return Err(TiffError::FormatError(
-                    TiffFormatError::StripTileTagConflict,
-                ))
+                    TiffFormatError::InconsistentSizesEncountered,
+                ));
             }
+
+            if rows_per_strip == 0 {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::InconsistentSizesEncountered,
+                ));
+            }
+
+            if u32::try_from(chunk_offsets.len())?
+                != height.div_ceil(rows_per_strip) * planes as u32
+            {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::IncorrectChunkCount {
+                        expected: height.div_ceil(rows_per_strip) * planes as u32,
+                        found: chunk_offsets.len() as u32,
+                    },
+                ));
+            }
+        } else if is_tiled && (has_strips || has_tiles) {
+            chunk_type = ChunkType::Tile;
+
+            let tile_width = usize::try_from(tag_reader.require_tag(Tag::TileWidth)?.into_u32()?)?;
+            let tile_length =
+                usize::try_from(tag_reader.require_tag(Tag::TileLength)?.into_u32()?)?;
+
+            // Prioritize tiles over strips, tiles are what we expect.
+            let (tag_offsets, tag_counts) = if has_tiles {
+                (Tag::TileOffsets, Tag::TileByteCounts)
+            } else {
+                (Tag::StripOffsets, Tag::StripByteCounts)
+            };
+
+            if tile_width == 0 {
+                return Err(TiffFormatError::InvalidTagValueType(Tag::TileWidth).into());
+            } else if tile_length == 0 {
+                return Err(TiffFormatError::InvalidTagValueType(Tag::TileLength).into());
+            }
+
+            strip_decoder = None;
+            tile_attributes = Some(TileAttributes {
+                image_width: usize::try_from(width)?,
+                image_height: usize::try_from(height)?,
+                tile_width,
+                tile_length,
+            });
+
+            chunk_offsets = tag_reader.find_tag(tag_offsets)?.unwrap().into_u64_vec()?;
+            chunk_bytes = tag_reader.find_tag(tag_counts)?.unwrap().into_u64_vec()?;
+
+            let tile = tile_attributes.as_ref().unwrap();
+
+            if chunk_offsets.len() != chunk_bytes.len() {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::InconsistentSizesEncountered,
+                ));
+            }
+
+            if chunk_offsets.len() != tile.tiles_down() * tile.tiles_across() * planes as usize {
+                return Err(TiffError::FormatError(
+                    TiffFormatError::IncorrectChunkCount {
+                        expected: (tile.tiles_down() * tile.tiles_across() * planes as usize)
+                            as u32,
+                        found: chunk_offsets.len() as u32,
+                    },
+                ));
+            }
+        } else {
+            return Err(TiffError::FormatError(
+                TiffFormatError::StripTileTagConflict,
+            ));
         };
 
         let mut sample_format = sample_format;
@@ -457,6 +449,31 @@ impl Image {
             bits_per_sample = 32;
         }
 
+        // Read ColorMap for palette images. The tag contains 3 * 2^BitsPerSample u16 entries.
+        let color_map = if photometric_interpretation == PhotometricInterpretation::RGBPalette {
+            match tag_reader.find_tag(Tag::ColorMap)? {
+                Some(v) => {
+                    let map = v.into_u16_vec()?;
+                    let expected_len = 3usize
+                        .checked_mul(1usize << bits_per_sample)
+                        .ok_or(TiffError::LimitsExceeded)?;
+                    if map.len() != expected_len {
+                        return Err(TiffError::FormatError(
+                            TiffFormatError::InconsistentSizesEncountered,
+                        ));
+                    }
+                    Some(map)
+                }
+                None => {
+                    return Err(TiffError::FormatError(
+                        TiffFormatError::RequiredTagNotFound(Tag::ColorMap),
+                    ));
+                }
+            }
+        } else {
+            None
+        };
+
         Ok(Image {
             width,
             height,
@@ -476,6 +493,8 @@ impl Image {
             chunk_offsets,
             chunk_bytes,
             chroma_subsampling,
+            fill_order,
+            color_map,
             decompression_to_host_endian: matches!(
                 compression_method,
                 CompressionMethod::SgiLog | CompressionMethod::SgiLog24
@@ -483,6 +502,17 @@ impl Image {
         })
     }
 
+    pub(crate) fn check_chunk_type(&self, expected: ChunkType) -> TiffResult<()> {
+        if expected != self.chunk_type {
+            return Err(TiffError::UsageError(UsageError::InvalidChunkType(
+                expected,
+                self.chunk_type,
+            )));
+        }
+
+        Ok(())
+    }
+
     pub(crate) fn colortype(&self) -> TiffResult<ColorType> {
         let is_alpha_extra_samples = matches!(
             self.extra_samples.as_slice(),
@@ -628,14 +658,13 @@ impl Image {
                     vec![self.bits_per_sample; self.samples as usize],
                 ),
             )),
-            PhotometricInterpretation::RGBPalette | PhotometricInterpretation::TransparencyMask => {
-                Err(TiffError::UnsupportedError(
-                    TiffUnsupportedError::InterpretationWithBits(
-                        self.photometric_interpretation,
-                        vec![self.bits_per_sample; self.samples as usize],
-                    ),
-                ))
-            }
+            PhotometricInterpretation::RGBPalette => Ok(ColorType::Palette(self.bits_per_sample)),
+            PhotometricInterpretation::TransparencyMask => Err(TiffError::UnsupportedError(
+                TiffUnsupportedError::InterpretationWithBits(
+                    self.photometric_interpretation,
+                    vec![self.bits_per_sample; self.samples as usize],
+                ),
+            )),
         }
     }
 
@@ -647,6 +676,7 @@ impl Image {
         #[cfg_attr(not(feature = "jpeg"), allow(unused_variables))] jpeg_tables: Option<&[u8]>,
         dimensions: (u32, u32),
         samples: u16,
+        #[cfg_attr(not(feature = "fax"), allow(unused_variables))] fill_order: u16,
     ) -> TiffResult<Box<dyn Read + 'r>> {
         Ok(match compression_method {
             CompressionMethod::None => Box::new(reader),
@@ -740,10 +770,18 @@ impl Image {
                 Box::new(Cursor::new(data))
             }
             #[cfg(feature = "fax")]
+            CompressionMethod::Fax3 => Box::new(super::stream::Group3Reader::new(
+                dimensions,
+                reader,
+                compressed_length,
+                fill_order,
+            )?),
+            #[cfg(feature = "fax")]
             CompressionMethod::Fax4 => Box::new(super::stream::Group4Reader::new(
                 dimensions,
                 reader,
                 compressed_length,
+                fill_order,
             )?),
             #[cfg(feature = "webp")]
             CompressionMethod::WebP => Box::new(super::stream::WebPReader::new(
@@ -842,24 +880,40 @@ impl Image {
 
         let data_dimensions = (width, height);
 
+        // Output bits per sample: sub-byte depths stay packed, supra-byte non-standard
+        // depths are promoted to the next standard width (matching sample_type() mapping).
+        let output_bits_per_sample: u8 = match tiff_bits_per_sample {
+            0..=8 => tiff_bits_per_sample,
+            9..=16 => 16,
+            17..=32 => 32,
+            _ => 64,
+        };
+
+        // Packed row size for reading from the file (uses tiff_bits_per_sample).
         let tiff_row_bits = (u64::from(tiff_chunk_dimensions.0) * u64::from(tiff_bits_per_sample))
             .checked_mul(u64::from(tiff_samples))
             .ok_or(TiffError::LimitsExceeded)?;
         let tiff_row_bytes: usize = tiff_row_bits.div_ceil(8).try_into()?;
 
-        let chunk_row_bits = (u64::from(tiff_chunk_dimensions.0) * u64::from(tiff_bits_per_sample))
-            .checked_mul(u64::from(data_samples))
-            .ok_or(TiffError::LimitsExceeded)?;
+        // Output buffer sizes use output_bits_per_sample (the promoted width).
+        let chunk_row_bits = (u64::from(tiff_chunk_dimensions.0)
+            * u64::from(output_bits_per_sample))
+        .checked_mul(u64::from(data_samples))
+        .ok_or(TiffError::LimitsExceeded)?;
         let chunk_row_bytes: usize = chunk_row_bits.div_ceil(8).try_into()?;
 
-        let data_row_bits = (u64::from(data_dimensions.0) * u64::from(tiff_bits_per_sample))
+        let data_row_bits = (u64::from(data_dimensions.0) * u64::from(output_bits_per_sample))
             .checked_mul(u64::from(data_samples))
             .ok_or(TiffError::LimitsExceeded)?;
         let data_row_bytes: usize = data_row_bits.div_ceil(8).try_into()?;
 
+        // Clamp the chunk height to the image height: a chunk never contributes more
+        // rows than the image contains. Without this, RowsPerStrip = u32::MAX overflows
+        // usize on 32-bit platforms.
+        let clamped_chunk_height = tiff_chunk_dimensions.1.min(data_dimensions.1);
         let chunk_col_stride: usize = data_row_bits
             .div_ceil(8)
-            .checked_mul(u64::from(tiff_chunk_dimensions.1))
+            .checked_mul(u64::from(clamped_chunk_height))
             .ok_or(TiffError::LimitsExceeded)?
             .try_into()?;
 
@@ -908,6 +962,7 @@ impl Image {
             chunk_col_stride,
             plane_stride,
             tiff_bits_per_sample,
+            output_bits_per_sample,
             tiff_samples,
             tiff_chunk_dimensions,
             tiff_row_bytes,
@@ -978,11 +1033,18 @@ impl Image {
             | ColorType::CMYKA(n)
             | ColorType::YCbCr(n)
             | ColorType::Gray(n)
+            | ColorType::Palette(n)
             | ColorType::Multiband {
                 bit_depth: n,
                 num_samples: _,
             } if n == 8 || n == 16 || n == 32 || n == 64 => {}
-            ColorType::Gray(n)
+            ColorType::RGB(n)
+            | ColorType::RGBA(n)
+            | ColorType::CMYK(n)
+            | ColorType::CMYKA(n)
+            | ColorType::YCbCr(n)
+            | ColorType::Gray(n)
+            | ColorType::Palette(n)
             | ColorType::Multiband {
                 bit_depth: n,
                 num_samples: _,
@@ -999,6 +1061,26 @@ impl Image {
                     ));
                 }
             },
+            // Extended bit depths (9-15, 17-31): packed N-bit samples unpacked to standard width.
+            // Horizontal predictor is supported (operates on unpacked standard-width samples).
+            // FloatingPoint predictor is not meaningful for non-standard integer depths.
+            ColorType::RGB(n)
+            | ColorType::RGBA(n)
+            | ColorType::CMYK(n)
+            | ColorType::CMYKA(n)
+            | ColorType::YCbCr(n)
+            | ColorType::Gray(n)
+            | ColorType::Multiband {
+                bit_depth: n,
+                num_samples: _,
+            } if n <= 32 => match self.predictor {
+                Predictor::None | Predictor::Horizontal => {}
+                Predictor::FloatingPoint => {
+                    return Err(TiffError::UnsupportedError(
+                        TiffUnsupportedError::FloatingPointPredictor(color_type),
+                    ));
+                }
+            },
             type_ => {
                 return Err(TiffError::UnsupportedError(
                     TiffUnsupportedError::UnsupportedColorType(type_),
@@ -1070,9 +1152,52 @@ impl Image {
             self.jpeg_tables.as_deref().map(|a| &**a),
             chunk_dims,
             self.samples,
+            self.fill_order,
         )?;
 
-        if is_output_chunk_rows && is_all_bits {
+        // Extended bit depths (9-15, 17-31): packed N-bit samples must be unpacked to
+        // standard-width output samples before endianness fix and predictor.
+        let needs_unpacking = layout.tiff_bits_per_sample != layout.output_bits_per_sample
+            && layout.tiff_bits_per_sample > 8;
+
+        if needs_unpacking {
+            if !is_all_bits {
+                // Packed extended depths with extra samples to discard is not yet supported.
+                return Err(TiffError::UnsupportedError(
+                    TiffUnsupportedError::InterpretationWithBits(
+                        self.photometric_interpretation,
+                        vec![self.bits_per_sample; self.samples as usize],
+                    ),
+                ));
+            }
+
+            let tiff_bps = layout.tiff_bits_per_sample;
+            let out_bps = layout.output_bits_per_sample;
+            let samples_per_data_row = data_dims.0 as usize * samples as usize;
+
+            let mut packed = vec![0u8; chunk_row_bytes];
+
+            for row in buf.chunks_mut(layout.row_stride).take(data_dims.1 as usize) {
+                reader.read_exact(&mut packed)?;
+
+                let out_row = &mut row[..data_row_bytes];
+                unpack_bits(&packed, out_row, tiff_bps, samples_per_data_row, out_bps);
+
+                // Unpacked values are in native byte order, so pass native to skip
+                // endianness conversion while still applying the predictor.
+                super::fix_endianness_and_predict(
+                    out_row,
+                    color_type.bit_depth(),
+                    samples,
+                    ByteOrder::native(),
+                    predictor,
+                );
+
+                if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                    super::invert_colors(out_row, color_type, self.sample_format)?;
+                }
+            }
+        } else if is_output_chunk_rows && is_all_bits {
             // Here we can read directly into the output buffer itself.
             let tile = &mut buf[..chunk_row_bytes * data_dims.1 as usize];
             reader.read_exact(tile)?;
@@ -1197,6 +1322,108 @@ impl Image {
     }
 }
 
+/// Unpack N-bit packed samples (MSB-first) into standard-width output samples in native byte
+/// order. Packed bits are read from `src` and expanded samples are written to `dst`.
+///
+/// `bits_per_sample` is the packed depth (e.g. 10, 12, 14).
+/// `num_samples` is the number of samples to extract.
+/// `output_width` is the output sample width in bits (16 or 32).
+///
+/// # Panics
+///
+/// Panics if `dst` is too small for `num_samples` output samples.
+fn unpack_bits(
+    src: &[u8],
+    dst: &mut [u8],
+    bits_per_sample: u8,
+    num_samples: usize,
+    output_width: u8,
+) {
+    // Dispatch to const-generic specializations so the compiler can unroll the
+    // byte-gathering loop and precompute shift/mask constants.
+    macro_rules! dispatch {
+        ($($bps:literal),+) => {
+            match bits_per_sample {
+                $( $bps => unpack_bits_const::<$bps>(src, dst, num_samples, output_width), )+
+                _ => unpack_bits_const::<0>(src, dst, num_samples, output_width),
+            }
+        };
+    }
+    // Cover every bit depth from 9..=32 that could reach this path, plus 0 as fallback.
+    dispatch!(
+        9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+        32
+    );
+}
+
+/// Inner loop with const BPS so the compiler can optimize the bit extraction.
+/// BPS=0 is the fallback for unexpected bit depths (uses runtime value).
+#[inline(always)]
+fn unpack_bits_const<const BPS: u8>(
+    src: &[u8],
+    dst: &mut [u8],
+    num_samples: usize,
+    output_width: u8,
+) {
+    debug_assert!(output_width == 16 || output_width == 32);
+
+    match output_width {
+        16 => {
+            debug_assert!(dst.len() >= num_samples * 2);
+            let mut bit_offset: usize = 0;
+            for i in 0..num_samples {
+                let val = if BPS > 0 {
+                    extract_bits_msb_const::<BPS>(src, bit_offset)
+                } else {
+                    extract_bits_msb_const::<16>(src, bit_offset) // unreachable fallback
+                };
+                dst[i * 2..i * 2 + 2].copy_from_slice(&(val as u16).to_ne_bytes());
+                bit_offset += if BPS > 0 { BPS as usize } else { 16 };
+            }
+        }
+        32 => {
+            debug_assert!(dst.len() >= num_samples * 4);
+            let mut bit_offset: usize = 0;
+            for i in 0..num_samples {
+                let val = if BPS > 0 {
+                    extract_bits_msb_const::<BPS>(src, bit_offset)
+                } else {
+                    extract_bits_msb_const::<32>(src, bit_offset) // unreachable fallback
+                };
+                dst[i * 4..i * 4 + 4].copy_from_slice(&val.to_ne_bytes());
+                bit_offset += if BPS > 0 { BPS as usize } else { 32 };
+            }
+        }
+        _ => unreachable!(),
+    }
+}
+
+/// Extract a value of `BPS` bits starting at `bit_offset` from an MSB-first packed byte stream.
+/// Uses a single wide read + shift/mask for branchless extraction.
+#[inline(always)]
+fn extract_bits_msb_const<const BPS: u8>(src: &[u8], bit_offset: usize) -> u32 {
+    let byte_idx = bit_offset / 8;
+    let bit_idx = bit_offset % 8;
+    let mask: u64 = (1u64 << BPS) - 1;
+
+    // Read a u64 from as many bytes as available, big-endian, without going out of bounds.
+    // For BPS <= 32 (+ up to 7 bits offset = 39 bits max), we need at most 5 bytes,
+    // but reading 8 at once is faster and the branch is only taken near row ends.
+    let remaining = src.len() - byte_idx;
+    let acc = if remaining >= 8 {
+        u64::from_be_bytes(src[byte_idx..byte_idx + 8].try_into().unwrap())
+    } else {
+        // Near the end of the buffer — read available bytes into the high bits of a u64.
+        let mut buf = [0u8; 8];
+        buf[..remaining].copy_from_slice(&src[byte_idx..]);
+        u64::from_be_bytes(buf)
+    };
+
+    // The value starts at bit_idx from the MSB of our u64. Shift it to the LSB and mask.
+    let shift = 64 - bit_idx - BPS as usize;
+    ((acc >> shift) & mask) as u32
+}
+
 impl ReadoutLayout {
     pub(crate) fn samples_per_out_texel(&self) -> u16 {
         match self.planar_config {
@@ -1209,7 +1436,7 @@ impl ReadoutLayout {
     // pixel data.
     pub(crate) fn chunk_row_bytes(&self, width: u32) -> TiffResult<usize> {
         let data_samples = self.samples_per_out_texel();
-        let data_row_bits = (u64::from(width) * u64::from(self.tiff_bits_per_sample))
+        let data_row_bits = (u64::from(width) * u64::from(self.output_bits_per_sample))
             .checked_mul(u64::from(data_samples))
             .ok_or(TiffError::LimitsExceeded)?;
         Ok(data_row_bits.div_ceil(8).try_into()?)
@@ -1227,8 +1454,12 @@ impl ReadoutLayout {
 
         let data_row_bytes = u64::try_from(row_stride)?;
 
+        // Use the original image height (from plane_stride / row_stride) to clamp
+        // the chunk height, matching the clamping in readout_for_size().
+        let image_height = self.plane_stride.checked_div(self.row_stride).unwrap_or(0) as u32;
+        let clamped_chunk_height = self.tiff_chunk_dimensions.1.min(image_height);
         let chunk_col_stride = data_row_bytes
-            .checked_mul(u64::from(self.tiff_chunk_dimensions.1))
+            .checked_mul(u64::from(clamped_chunk_height))
             .ok_or(TiffError::LimitsExceeded)?
             .try_into()?;
 

src/decoder/stream.rs

@@ -256,9 +256,24 @@ impl<R: Read> Read for PackBitsReader<R> {
     }
 }
 
+/// Iterator adapter that reverses bits in each byte for FillOrder=2 (LSB-to-MSB).
+#[cfg(feature = "fax")]
+type FaxBytes<R> =
+    core::iter::Map<io::Bytes<io::BufReader<io::Take<R>>>, fn(io::Result<u8>) -> io::Result<u8>>;
+
+#[cfg(feature = "fax")]
+fn fax_byte_iter<R: Read>(reader: R, len: u64, fill_order: u16) -> FaxBytes<R> {
+    let map_fn: fn(io::Result<u8>) -> io::Result<u8> = if fill_order == 2 {
+        |r| r.map(u8::reverse_bits)
+    } else {
+        |r| r
+    };
+    io::BufReader::new(reader.take(len)).bytes().map(map_fn)
+}
+
 #[cfg(feature = "fax")]
 pub struct Group4Reader<R: Read> {
-    decoder: fax34::decoder::Group4Decoder<io::Bytes<io::BufReader<io::Take<R>>>>,
+    decoder: fax34::decoder::Group4Decoder<FaxBytes<R>>,
     line_buf: io::Cursor<Vec<u8>>,
     height: u32,
     width: u16,
@@ -271,13 +286,14 @@ impl<R: Read> Group4Reader<R> {
         dimensions: (u32, u32),
         reader: R,
         compressed_length: u64,
+        fill_order: u16,
     ) -> crate::TiffResult<Self> {
         let width = u16::try_from(dimensions.0)?;
         let height = dimensions.1;
 
         Ok(Self {
             decoder: fax34::decoder::Group4Decoder::new(
-                io::BufReader::new(reader.take(compressed_length)).bytes(),
+                fax_byte_iter(reader, compressed_length, fill_order),
                 width,
             )?,
             line_buf: io::Cursor::new(Vec::with_capacity(width.into())),
@@ -356,6 +372,141 @@ impl<R: Read> Read for Group4Reader<R> {
     }
 }
 
+/// Owning byte reader for Group 3 decoding: the compressed data is consumed
+/// into an iterator so the reader doesn't borrow the buffer.
+#[cfg(feature = "fax")]
+type OwnedBitReader = fax34::ByteReader<
+    core::iter::Map<std::vec::IntoIter<u8>, fn(u8) -> Result<u8, std::convert::Infallible>>,
+>;
+
+/// Decodes CCITT Group 3 (T.4) 1D compressed data line by line.
+///
+/// The fax crate's `Group3Decoder` has a bug where `new()` doesn't consume the
+/// initial EOL marker, causing its lookup tables to destructively consume bits
+/// from the EOL when trying to decode run-length codes. We work around this by
+/// using the crate's lower-level `white::decode` / `black::decode` functions
+/// and handling EOL markers ourselves.
+#[cfg(feature = "fax")]
+pub struct Group3Reader {
+    reader: OwnedBitReader,
+    line_buf: io::Cursor<Vec<u8>>,
+    height: u32,
+    width: u16,
+    y: u32,
+}
+
+#[cfg(feature = "fax")]
+impl Group3Reader {
+    pub fn new<R: Read>(
+        dimensions: (u32, u32),
+        reader: R,
+        compressed_length: u64,
+        fill_order: u16,
+    ) -> crate::TiffResult<Self> {
+        let width = u16::try_from(dimensions.0)?;
+        let height = dimensions.1;
+
+        // Buffer all compressed data and apply FillOrder bit reversal
+        let mut compressed = vec![0u8; compressed_length as usize];
+        reader.take(compressed_length).read_exact(&mut compressed)?;
+        if fill_order == 2 {
+            for b in &mut compressed {
+                *b = b.reverse_bits();
+            }
+        }
+
+        // Create an owning bit reader (Vec consumed by into_iter, no borrow issues)
+        let map_fn: fn(u8) -> Result<u8, std::convert::Infallible> = Ok;
+        let mut bit_reader = fax34::ByteReader::new(compressed.into_iter().map(map_fn)).unwrap();
+
+        // Skip fill bits + initial EOL marker
+        Self::skip_eol(&mut bit_reader);
+
+        Ok(Self {
+            reader: bit_reader,
+            line_buf: io::Cursor::new(Vec::with_capacity(width.into())),
+            width,
+            height,
+            y: 0,
+        })
+    }
+
+    /// Skip zero fill bits followed by the terminating '1' bit of an EOL code.
+    fn skip_eol(reader: &mut impl fax34::BitReader) {
+        while reader.peek(1) == Some(0) {
+            let _ = reader.consume(1);
+        }
+        if reader.peek(1) == Some(1) {
+            let _ = reader.consume(1);
+        }
+    }
+
+    /// Decode a full run-length value (terminal + optional makeup codes).
+    fn with_markup<R: fax34::BitReader>(
+        decoder: fn(&mut R) -> Option<u16>,
+        reader: &mut R,
+    ) -> Option<u16> {
+        let mut sum = 0u16;
+        while let Some(n) = decoder(reader) {
+            sum += n;
+            if n < 64 {
+                return Some(sum);
+            }
+        }
+        None
+    }
+}
+
+#[cfg(feature = "fax")]
+impl Read for Group3Reader {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        if self.line_buf.position() as usize == self.line_buf.get_ref().len()
+            && self.y < self.height
+        {
+            // Decode one line of alternating white/black run-lengths
+            let mut transitions = Vec::new();
+            let mut a0 = 0u16;
+            let mut is_white = true;
+            loop {
+                let run = if is_white {
+                    Self::with_markup(fax34::maps::white::decode, &mut self.reader)
+                } else {
+                    Self::with_markup(fax34::maps::black::decode, &mut self.reader)
+                };
+                match run {
+                    Some(len) => {
+                        a0 += len;
+                        transitions.push(a0);
+                        is_white = !is_white;
+                    }
+                    None => break,
+                }
+            }
+
+            self.y += 1;
+
+            // Convert transitions to packed bilevel output
+            let bytes_per_line = usize::from(self.width).div_ceil(8);
+            let buffer = self.line_buf.get_mut();
+            buffer.clear();
+            buffer.resize(bytes_per_line, 0u8);
+
+            let pels = fax34::decoder::pels(&transitions, self.width);
+            for (i, c) in pels.enumerate() {
+                if c == fax34::Color::Black {
+                    buffer[i / 8] |= 1 << (7 - (i % 8));
+                }
+            }
+            self.line_buf.set_position(0);
+
+            // Skip fill bits + line-ending EOL
+            Self::skip_eol(&mut self.reader);
+        }
+
+        self.line_buf.read(buf)
+    }
+}
+
 #[cfg(feature = "webp")]
 pub struct WebPReader {
     inner: Cursor<Vec<u8>>,

src/directory.rs

@@ -18,6 +18,7 @@ use crate::{
 /// [`Decoder::read_directory_tags`](crate::decoder::Decoder::read_directory_tags) to read the
 /// values associated with tags from an underlying file.
 #[doc(alias = "IFD")]
+#[derive(Clone)]
 pub struct Directory {
     /// There are at most `u16::MAX` entries in any single directory, the count is stored as a
     /// 2-byte value. The order in the file is implied to be ascending by tag value (the decoder

src/encoder/compression/deflate.rs

@@ -7,24 +7,15 @@ pub struct Deflate {
     level: FlateCompression,
 }
 
-/// The level of compression used by the Deflate algorithm.
-/// It allows trading compression ratio for compression speed.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-#[non_exhaustive]
-#[derive(Default)]
-pub enum DeflateLevel {
-    /// The fastest possible compression mode.
-    Fast = 1,
-    /// The conserative choice between speed and ratio.
-    #[default]
-    Balanced = 6,
-    /// The best compression available with Deflate.
-    Best = 9,
-}
-
 impl Deflate {
     /// Create a new deflate compressor with a specific level of compression.
-    pub fn with_level(level: DeflateLevel) -> Self {
+    ///
+    /// The valid levels are 1 through 9 inclusive. The default level is 6.
+    ///
+    /// - `1` stands for light but fast compression
+    /// - `6` is the recommended balanced default
+    /// - `9` is maximum compression ratio at the cost of slow encoding
+    pub fn with_level(level: u8) -> Self {
         Self {
             level: FlateCompression::new(level as u32),
         }
@@ -33,7 +24,7 @@ impl Deflate {
 
 impl Default for Deflate {
     fn default() -> Self {
-        Self::with_level(DeflateLevel::default())
+        Self::with_level(6)
     }
 }
 

src/encoder/compression/mod.rs

@@ -9,7 +9,7 @@ mod packbits;
 mod uncompressed;
 
 #[cfg(feature = "deflate")]
-pub use self::deflate::{Deflate, DeflateLevel};
+pub use self::deflate::Deflate;
 
 #[cfg(feature = "lzw")]
 pub use self::lzw::Lzw;

src/encoder/mod.rs

@@ -38,17 +38,26 @@ use self::writer::*;
 /// [Predictor::Horizontal] is for integer sample types.
 /// [Predictor::FloatingPoint] is for floating-point sample types (f32, f64).
 pub type Predictor = crate::tags::Predictor;
-#[cfg(feature = "deflate")]
-pub type DeflateLevel = compression::DeflateLevel;
 
-#[derive(Clone, Copy, PartialEq, Default)]
+#[non_exhaustive]
+#[derive(Debug, Clone, Copy, PartialEq, Default)]
 pub enum Compression {
+    /// No compression whatsoever. Fastest but produces large files.
     #[default]
     Uncompressed,
+    /// Legacy [LZW](https://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch) algorithm. Not recommended, use DEFLATE instead.
     #[cfg(feature = "lzw")]
     Lzw,
+    /// [DEFLATE](https://en.wikipedia.org/wiki/DEFLATE) algorithm with the specified compression level.
+    ///
+    /// The valid levels are 1 through 9 inclusive. The default level is 6.
+    ///
+    /// - `1` stands for light but fast compression
+    /// - `6` is the recommended balanced default
+    /// - `9` is maximum compression ratio at the cost of slow encoding
     #[cfg(feature = "deflate")]
-    Deflate(DeflateLevel),
+    Deflate(u8),
+    /// [PackBits](https://en.wikipedia.org/wiki/PackBits) compression, a variant of RLE compression scheme. Fast, primitive compression with a poor compression ratio.
     Packbits,
 }
 
@@ -154,7 +163,15 @@ impl<W: Write + Seek, K: TiffKind> TiffEncoder<W, K> {
     /// Set the predictor to use
     ///
     /// A predictor is used to simplify the file before writing it. This is very
-    /// useful when writing a file compressed using LZW as it can improve efficiency
+    /// useful when writing a file compressed using LZW or DEFLATE as it can improve compression ratio
+    ///
+    /// The floating-point predictor is not universally supported. While most software can handle it,
+    /// Safari, Mac OS Preview and ImageJ Java library cannot. Don't use a predictor for float data
+    /// for maximum compatibility at the cost of compression ratio.
+    ///
+    /// The chosen predictor should match the data type being encoded.
+    /// Encoding floating-point data with `Predictor::Horizontal` is technically possible,
+    /// but rarely beneficial, and some decoders may reject such files.
     pub fn with_predictor(mut self, predictor: Predictor) -> Self {
         self.predictor = predictor;
 
@@ -471,7 +488,8 @@ impl<'a, W: 'a + Write + Seek, K: TiffKind> DirectoryEncoder<'a, W, K> {
             self.writer.write_u16(entry.field_type().to_u16())?;
             let count = K::convert_offset(entry.count())?;
             count.write(self.writer)?;
-            self.writer.write_bytes(&entry.offset()[..offset_bytes])?;
+            self.writer
+                .write_bytes(&entry.offset_raw()[..offset_bytes])?;
         }
 
         Ok(offset)
@@ -837,9 +855,7 @@ impl<'a, W: 'a + Write + Seek, T: ColorType, K: TiffKind> ImageEncoder<'a, W, T,
         self.encoder
             .write_tag(Tag::ResolutionUnit, unit.to_u16())
             .unwrap();
-        self.encoder
-            .write_tag(Tag::XResolution, value.clone())
-            .unwrap();
+        self.encoder.write_tag(Tag::XResolution, value).unwrap();
         self.encoder.write_tag(Tag::YResolution, value).unwrap();
     }
 

src/encoder/tiff_value.rs

@@ -665,22 +665,22 @@ impl_tiff_value_for_contiguous_sequence!(Rational; 8; Type::RATIONAL);
 impl_tiff_value_for_contiguous_sequence!(SRational; 8; Type::SRATIONAL);
 
 /// Type to represent tiff values of type `IFD`
-#[derive(Clone)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct Ifd(pub u32);
 
 /// Type to represent tiff values of type `IFD8`
-#[derive(Clone)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct Ifd8(pub u64);
 
 /// Type to represent tiff values of type `RATIONAL`
-#[derive(Clone)]
+#[derive(Debug, Copy, Clone)]
 pub struct Rational {
     pub n: u32,
     pub d: u32,
 }
 
 /// Type to represent tiff values of type `SRATIONAL`
-#[derive(Clone)]
+#[derive(Debug, Copy, Clone)]
 pub struct SRational {
     pub n: i32,
     pub d: i32,

src/encoder/writer.rs

@@ -221,7 +221,7 @@ fn encoder_on_short_writes() {
     };
 
     let imgdata = vec![42u8; 100 * 100];
-    let mut data = crate::decoder::DecodingResult::U8(vec![]);
+    let mut data = crate::decoder::DecodingSampleBuffer::U8(vec![]);
 
     for comp in [
         super::Compression::Uncompressed,
@@ -247,7 +247,7 @@ fn encoder_on_short_writes() {
         let _layout = tiff_reader.read_image_to_buffer(&mut data).unwrap();
 
         assert!(
-            matches!(&data, crate::decoder::DecodingResult::U8(v) if *v == imgdata),
+            matches!(&data, crate::decoder::DecodingSampleBuffer::U8(v) if *v == imgdata),
             "{data:?} @ {}",
             data.as_buffer(0).byte_len()
         );

src/tags.rs

@@ -426,7 +426,24 @@ impl ValueBuffer {
     }
 
     /// Create a value with native byte order from in-memory data.
-    pub fn from_value<T: TiffValue>(value: &T) -> Self {
+    ///
+    /// This is equivalent to calling [`Self::set_value`] on a newly created buffer.
+    ///
+    /// # Example
+    ///
+    /// Create a buffer representing a particular tag's value:
+    ///
+    /// ```
+    /// use tiff::tags::{ByteOrder, CompressionMethod, ValueBuffer};
+    ///
+    /// // A buffer with initial content, for instance a tag's value.
+    /// let buffer = ValueBuffer::from_value(&CompressionMethod::ModernJPEG);
+    /// assert_eq!(buffer.as_bytes().len(), 2);
+    ///
+    /// // Note that depends on host endianess which of these holds:
+    /// assert!(buffer.as_bytes() == [0, 7] || buffer.as_bytes() == [7, 0]);
+    /// ```
+    pub fn from_value<T: TiffValue + ?Sized>(value: &T) -> Self {
         ValueBuffer {
             bytes: value.data().into_owned(),
             ty: <T as TiffValue>::FIELD_TYPE,
@@ -435,6 +452,42 @@ impl ValueBuffer {
         }
     }
 
+    /// Set the buffer to the defined value.
+    ///
+    /// The previous data is erased. This converts the value's representation to the byte order of
+    /// the buffer in the process (which is a no-op if the buffer uses host byte order).
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use tiff::tags::{ByteOrder, CompressionMethod, ValueBuffer};
+    ///
+    /// // A buffer with initial content, for instance a tag's value.
+    /// let mut buffer = ValueBuffer::from_value(&CompressionMethod::JPEG);
+    /// assert_eq!(buffer.as_bytes().len(), 2);
+    ///
+    /// // Ensure a host-independent byte order for the following representation.
+    /// buffer.set_byte_order(ByteOrder::LittleEndian);
+    /// // slices and arrays of primitives are a possible `TiffValue`
+    /// buffer.set_value(&[0, 1, 42u16]);
+    ///
+    /// // The little endian representation of these numbers (2 bytes each)
+    /// assert_eq!(buffer.as_bytes(), [0, 0, 1, 0, 42, 0]);
+    /// ```
+    pub fn set_value<T: TiffValue + ?Sized>(&mut self, value: &T) {
+        self.bytes.clear();
+
+        match value.data() {
+            std::borrow::Cow::Borrowed(slice) => self.bytes.extend_from_slice(slice),
+            std::borrow::Cow::Owned(ref mut data) => self.bytes.append(data),
+        }
+
+        self.ty = <T as TiffValue>::FIELD_TYPE;
+        self.count = value.count() as u64;
+
+        ByteOrder::native().convert(self.ty, &mut self.bytes, self.byte_order);
+    }
+
     pub fn byte_order(&self) -> ByteOrder {
         self.byte_order
     }
@@ -514,6 +567,13 @@ impl ValueBuffer {
     }
 }
 
+/// Create an empty value buffer with `Byte` type. This type choice is arbitrary.
+impl Default for ValueBuffer {
+    fn default() -> Self {
+        ValueBuffer::empty(Type::BYTE)
+    }
+}
+
 /// Byte order of the TIFF file.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum ByteOrder {

tests/decode_bigtiff_images.rs

@@ -26,21 +26,20 @@ fn test_big_tiff() {
             decoder.colortype().expect("Cannot get colortype"),
             ColorType::RGB(8)
         );
+
+        let mut ifd = decoder.current_ifd();
         assert_eq!(
-            decoder
-                .get_tag_u64(Tag::StripOffsets)
+            ifd.get_tag_u64(Tag::StripOffsets)
                 .expect("Cannot get StripOffsets"),
             16
         );
         assert_eq!(
-            decoder
-                .get_tag_u64(Tag::RowsPerStrip)
+            ifd.get_tag_u64(Tag::RowsPerStrip)
                 .expect("Cannot get RowsPerStrip"),
             64
         );
         assert_eq!(
-            decoder
-                .get_tag_u64(Tag::StripByteCounts)
+            ifd.get_tag_u64(Tag::StripByteCounts)
                 .expect("Cannot get StripByteCounts"),
             12288
         )

tests/decode_fp16_images.rs

@@ -1,6 +1,6 @@
 extern crate tiff;
 
-use tiff::decoder::{Decoder, DecodingResult};
+use tiff::decoder::{Decoder, DecodingSampleBuffer};
 use tiff::ColorType;
 
 use std::fs::File;
@@ -28,7 +28,7 @@ fn test_white_ieee_fp16() {
             ColorType::Gray(16)
         );
 
-        if let DecodingResult::F16(img) = decoder.read_image().unwrap() {
+        if let DecodingSampleBuffer::F16(img) = decoder.read_image().unwrap() {
             for p in img {
                 assert!(p == half::f16::from_f32_const(1.0));
             }
@@ -58,7 +58,7 @@ fn test_one_black_pixel_ieee_fp16() {
             ColorType::Gray(16)
         );
 
-        if let DecodingResult::F16(img) = decoder.read_image().unwrap() {
+        if let DecodingSampleBuffer::F16(img) = decoder.read_image().unwrap() {
             for (i, p) in img.iter().enumerate() {
                 if i == 0 {
                     assert!(p < &half::f16::from_f32_const(0.001));
@@ -92,7 +92,7 @@ fn test_pattern_horizontal_differencing_ieee_fp16() {
             ColorType::Gray(16)
         );
 
-        if let DecodingResult::F16(img) = decoder.read_image().unwrap() {
+        if let DecodingSampleBuffer::F16(img) = decoder.read_image().unwrap() {
             // 0, 2, 5, 8, 12, 16, 255 are black
             let black = [0, 2, 5, 8, 12, 16, 255];
             for (i, p) in img.iter().enumerate() {
@@ -128,7 +128,7 @@ fn test_pattern_predictor_ieee_fp16() {
             ColorType::Gray(16)
         );
 
-        if let DecodingResult::F16(img) = decoder.read_image().unwrap() {
+        if let DecodingSampleBuffer::F16(img) = decoder.read_image().unwrap() {
             // 0, 2, 5, 8, 12, 16, 255 are black
             let black = [0, 2, 5, 8, 12, 16, 255];
             for (i, p) in img.iter().enumerate() {
@@ -199,7 +199,7 @@ fn test_predictor_ieee_fp16() {
             ColorType::Gray(16)
         );
 
-        if let DecodingResult::F16(img) = decoder.read_image().unwrap() {
+        if let DecodingSampleBuffer::F16(img) = decoder.read_image().unwrap() {
             for (exp, found) in std::iter::zip(pnm_values.iter(), img.iter()) {
                 assert!((exp - found.to_f32()).abs() < 0.0001);
             }

tests/decode_geotiff_images.rs

@@ -1,6 +1,6 @@
 extern crate tiff;
 
-use tiff::decoder::{Decoder, DecodingResult};
+use tiff::decoder::{Decoder, DecodingSampleBuffer};
 use tiff::tags::Tag;
 use tiff::ColorType;
 
@@ -30,33 +30,31 @@ fn test_geo_tiff() {
                 num_samples: 5
             }
         );
+
+        let mut ifd = decoder.current_ifd();
         assert_eq!(
-            decoder
-                .get_tag_u64(Tag::StripOffsets)
+            ifd.get_tag_u64(Tag::StripOffsets)
                 .expect("Cannot get StripOffsets"),
             418
         );
         assert_eq!(
-            decoder
-                .get_tag_u64(Tag::RowsPerStrip)
+            ifd.get_tag_u64(Tag::RowsPerStrip)
                 .expect("Cannot get RowsPerStrip"),
             10
         );
         assert_eq!(
-            decoder
-                .get_tag_u64(Tag::StripByteCounts)
+            ifd.get_tag_u64(Tag::StripByteCounts)
                 .expect("Cannot get StripByteCounts"),
             1000
         );
         assert_eq!(
-            decoder
-                .get_tag(Tag::ModelPixelScaleTag)
+            ifd.get_tag(Tag::ModelPixelScaleTag)
                 .expect("Cannot get pixel scale")
                 .into_f64_vec()
                 .expect("Cannot get pixel scale"),
             vec![60.0, 60.0, 0.0]
         );
-        let DecodingResult::I16(data) = decoder.read_image().unwrap() else {
+        let DecodingSampleBuffer::I16(data) = decoder.read_image().unwrap() else {
             panic!("Cannot read band data")
         };
         assert_eq!(data.len(), 500);
@@ -67,7 +65,7 @@ fn test_geo_tiff() {
 #[test]
 fn test_webp_tiff() {
     let filenames = ["usda_naip_256_webp_z3.tif"];
-    let mut buffer = DecodingResult::U8(vec![]);
+    let mut buffer = DecodingSampleBuffer::U8(vec![]);
 
     for filename in filenames.iter() {
         let path = PathBuf::from(TEST_IMAGE_DIR).join(filename);

tests/decode_images.rs

@@ -1,6 +1,7 @@
 extern crate tiff;
 
-use tiff::decoder::{ifd, Decoder, DecodingResult};
+use tiff::decoder::{ifd, Decoder, DecodingSampleBuffer};
+use tiff::tags::{ByteOrder, Type};
 use tiff::ColorType;
 
 use std::fs::File;
@@ -8,6 +9,7 @@ use std::io::{Read, Seek};
 use std::path::PathBuf;
 
 const TEST_IMAGE_DIR: &str = "./tests/images/";
+const SEQ_IMAGE_DIR: &str = "./tests/images/seq/";
 
 macro_rules! test_image_sum {
     ($name:ident, $buffer:ident, $sum_ty:ty) => {
@@ -21,7 +23,7 @@ macro_rules! test_image_sum {
             let img_res = decoder.read_image().unwrap();
 
             match img_res {
-                DecodingResult::$buffer(res) => {
+                DecodingSampleBuffer::$buffer(res) => {
                     let sum: $sum_ty = res.into_iter().map(<$sum_ty>::from).sum();
                     assert_eq!(sum, expected_sum);
                 }
@@ -40,9 +42,198 @@ test_image_sum!(test_image_sum_u64, U64, u64);
 test_image_sum!(test_image_sum_f32, F32, f32);
 test_image_sum!(test_image_sum_f64, F64, f64);
 
+/// Compute a CRC32 hash of the full decoded TIFF output including metadata.
+///
+/// Hashes: page count, and for each page: dimensions, color type, and decoded
+/// sample data (in little-endian byte order for multi-byte types). This catches
+/// wrong dimensions, wrong color type, byte-order errors, bit-alignment errors,
+/// stride/padding errors, and pixel value errors.
+fn compute_tiff_hash<R: Read + Seek>(reader: R) -> u32 {
+    let mut decoder = Decoder::open(reader).expect("Cannot create decoder");
+    let mut hasher = crc32fast::Hasher::new();
+
+    let mut page = 0u32;
+    loop {
+        decoder.next_image().expect("Cannot read image IFD");
+        let (width, height) = decoder.dimensions().unwrap();
+        let color_type = decoder.colortype().unwrap();
+        let mut result = decoder.read_image().unwrap();
+
+        // Hash page index + dimensions
+        hasher.update(&page.to_le_bytes());
+        hasher.update(&width.to_le_bytes());
+        hasher.update(&height.to_le_bytes());
+
+        // Hash color type (discriminant + fields)
+        match color_type {
+            ColorType::Gray(n) => hasher.update(&[0, n]),
+            ColorType::RGB(n) => hasher.update(&[1, n]),
+            ColorType::Palette(n) => hasher.update(&[2, n]),
+            ColorType::GrayA(n) => hasher.update(&[3, n]),
+            ColorType::RGBA(n) => hasher.update(&[4, n]),
+            ColorType::CMYK(n) => hasher.update(&[5, n]),
+            ColorType::CMYKA(n) => hasher.update(&[6, n]),
+            ColorType::YCbCr(n) => hasher.update(&[7, n]),
+            ColorType::Lab(n) => hasher.update(&[8, n]),
+            ColorType::Multiband {
+                bit_depth,
+                num_samples,
+            } => {
+                hasher.update(&[9, bit_depth]);
+                hasher.update(&num_samples.to_le_bytes());
+            }
+            other => panic!("compute_tiff_hash: unhandled ColorType {other:?}"),
+        }
+
+        // Hash decoded data: TIFF type tag (u16 repr) + LE sample bytes.
+        // Map each variant to the corresponding TIFF Type for byte-order normalization.
+        let sample_type = match &result {
+            DecodingSampleBuffer::U8(_) => Type::BYTE,
+            DecodingSampleBuffer::I8(_) => Type::SBYTE,
+            DecodingSampleBuffer::U16(_) => Type::SHORT,
+            DecodingSampleBuffer::I16(_) => Type::SSHORT,
+            DecodingSampleBuffer::U32(_) => Type::LONG,
+            DecodingSampleBuffer::I32(_) => Type::SLONG,
+            DecodingSampleBuffer::F32(_) => Type::FLOAT,
+            DecodingSampleBuffer::U64(_) => Type::LONG8,
+            DecodingSampleBuffer::I64(_) => Type::SLONG8,
+            DecodingSampleBuffer::F64(_) => Type::DOUBLE,
+            DecodingSampleBuffer::F16(_) => Type::SHORT, // f16 is 2 bytes like SHORT
+        };
+        hasher.update(&sample_type.to_u16().to_le_bytes());
+
+        let mut buf = result.as_buffer(0);
+        let bytes = buf.as_bytes_mut();
+        ByteOrder::native().convert(sample_type, bytes, ByteOrder::LittleEndian);
+        hasher.update(bytes);
+
+        page += 1;
+        if !decoder.more_images() {
+            break;
+        }
+    }
+
+    // Hash total page count at the end
+    hasher.update(&page.to_le_bytes());
+    hasher.finalize()
+}
+
+/// Verify all TIFF files in tests/images/seq/ against their filename-embedded CRC32 hash.
+///
+/// Each file is named `<description>-<8hex>.tiff` where the last segment before `.tiff`
+/// is the expected CRC32 hash of (dimensions, color type, decoded data) for all pages.
+#[test]
+fn verify_all_seq_images() {
+    let seq_dir = std::path::Path::new(SEQ_IMAGE_DIR);
+    if !seq_dir.is_dir() {
+        panic!("seq image directory not found: {}", seq_dir.display());
+    }
+
+    let mut files: Vec<_> = std::fs::read_dir(seq_dir)
+        .expect("Cannot read seq image directory")
+        .filter_map(|e| e.ok())
+        .filter(|e| {
+            e.path()
+                .extension()
+                .is_some_and(|ext| ext == "tiff" || ext == "tif")
+        })
+        .collect();
+    files.sort_by_key(|e| e.file_name());
+
+    assert!(
+        !files.is_empty(),
+        "No .tiff files found in {}",
+        seq_dir.display()
+    );
+
+    let mut failures = Vec::new();
+    for entry in &files {
+        let path = entry.path();
+        let stem = path.file_stem().unwrap().to_str().unwrap();
+
+        // Extract expected hash: last '-'-delimited segment
+        let expected_hash = stem
+            .rsplit('-')
+            .next()
+            .expect("filename must contain a '-' before the hash");
+
+        // Validate it looks like an 8-char hex string
+        if expected_hash.len() != 8 || !expected_hash.chars().all(|c| c.is_ascii_hexdigit()) {
+            failures.push(format!(
+                "{}: filename does not end with 8-char hex hash (got '{}')",
+                stem, expected_hash
+            ));
+            continue;
+        }
+
+        let file = File::open(&path).expect("Cannot open test image");
+        let actual_hash = format!("{:08x}", compute_tiff_hash(file));
+
+        if actual_hash != expected_hash {
+            failures.push(format!(
+                "{}: expected hash {} but got {}",
+                stem, expected_hash, actual_hash
+            ));
+        }
+    }
+
+    if !failures.is_empty() {
+        panic!(
+            "{} of {} seq images failed hash verification:\n  {}",
+            failures.len(),
+            files.len(),
+            failures.join("\n  ")
+        );
+    }
+
+    eprintln!("Verified {} seq images", files.len());
+}
+
+/// Helper: print the correct hash-suffixed filename for every *.tiff in tests/images/seq/.
+/// Run with: cargo test print_seq_hashes -- --ignored --nocapture
+#[test]
+#[ignore]
+fn print_seq_hashes() {
+    let dir = std::path::Path::new(SEQ_IMAGE_DIR);
+    let mut files: Vec<_> = std::fs::read_dir(dir)
+        .expect("Cannot read image directory")
+        .filter_map(|e| e.ok())
+        .filter(|e| {
+            e.file_name()
+                .to_str()
+                .is_some_and(|n| n.starts_with("seq-") && n.ends_with(".tiff"))
+        })
+        .collect();
+    files.sort_by_key(|e| e.file_name());
+
+    for entry in &files {
+        let path = entry.path();
+        let name = path.file_name().unwrap().to_str().unwrap();
+        let file = File::open(&path).expect("Cannot open test image");
+        let hash = format!("{:08x}", compute_tiff_hash(file));
+        // Strip the old hash (last -XXXXXXXX before .tiff) if present
+        let stem = path.file_stem().unwrap().to_str().unwrap();
+        let base = match stem.rsplit_once('-') {
+            Some((prefix, suffix))
+                if suffix.len() == 8 && suffix.chars().all(|c| c.is_ascii_hexdigit()) =>
+            {
+                prefix
+            }
+            _ => stem,
+        };
+        let new_name = format!("{base}-{hash}.tiff");
+        if new_name != name {
+            eprintln!("RENAME: {name} -> {new_name}");
+        } else {
+            eprintln!("OK: {name}");
+        }
+    }
+}
+
 /// Tests that a decoder can be constructed for an image and the color type
 /// read from the IFD and is of the appropriate type, but the type is
 /// unsupported.
+#[allow(dead_code)]
 fn test_image_color_type_unsupported(file: &str, expected_type: ColorType) {
     let path = PathBuf::from(TEST_IMAGE_DIR).join(file);
     let img_file = File::open(path).expect("Cannot find test image!");
@@ -73,6 +264,47 @@ fn test_cmyk_f32() {
     test_image_sum_f32("cmyk-3c-32b-float.tiff", ColorType::CMYK(32), 496.0405);
 }
 
+#[test]
+fn test_palette_u1() {
+    test_image_sum_u8("palette-1c-1b.tiff", ColorType::Palette(1), 379313);
+}
+
+#[test]
+fn test_palette_u4() {
+    test_image_sum_u8("palette-1c-4b.tiff", ColorType::Palette(4), 1480490);
+}
+
+#[test]
+fn test_palette_u8() {
+    test_image_sum_u8("palette-1c-8b.tiff", ColorType::Palette(8), 2876948);
+}
+
+#[test]
+fn test_palette_color_map() {
+    let path = PathBuf::from(TEST_IMAGE_DIR).join("palette-1c-8b.tiff");
+    let img_file = File::open(path).expect("Cannot find test image!");
+    let mut decoder = Decoder::open(img_file).expect("Cannot create decoder");
+    decoder.next_image().expect("Cannot read image IFD");
+
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Palette(8));
+
+    let color_map = decoder
+        .color_map()
+        .expect("Palette image should have a color map");
+    // 8-bit palette: 3 * 256 = 768 entries
+    assert_eq!(color_map.len(), 768);
+
+    // Each section (R, G, B) has 256 entries
+    let r = &color_map[..256];
+    let g = &color_map[256..512];
+    let b = &color_map[512..768];
+
+    // Verify all values are valid u16 (non-zero palette, at least some variation)
+    assert!(r.iter().any(|&v| v > 0));
+    assert!(g.iter().any(|&v| v > 0));
+    assert!(b.iter().any(|&v| v > 0));
+}
+
 #[test]
 fn test_gray_u8() {
     test_image_sum_u8("minisblack-1c-8b.tiff", ColorType::Gray(8), 2840893);
@@ -80,7 +312,7 @@ fn test_gray_u8() {
 
 #[test]
 fn test_gray_u12() {
-    test_image_color_type_unsupported("12bit.cropped.tiff", ColorType::Gray(12));
+    test_image_sum_u16("12bit.cropped.tiff", ColorType::Gray(12), 10973);
 }
 
 #[test]
@@ -119,7 +351,7 @@ fn test_rgb_u8() {
 
 #[test]
 fn test_rgb_u12() {
-    test_image_color_type_unsupported("12bit.cropped.rgb.tiff", ColorType::RGB(12));
+    test_image_sum_u16("12bit.cropped.rgb.tiff", ColorType::RGB(12), 32919);
 }
 
 #[test]
@@ -172,7 +404,10 @@ fn test_string_tags() {
         let img_file = File::open(path).expect("Cannot find test image!");
         let mut decoder = Decoder::open(img_file).expect("Cannot create decoder");
         decoder.next_image().expect("Cannot read image IFD");
-        let software = decoder.get_tag(tiff::tags::Tag::Software).unwrap();
+        let software = decoder
+            .current_ifd()
+            .get_tag(tiff::tags::Tag::Software)
+            .unwrap();
         match software {
             ifd::Value::Ascii(s) => assert_eq!(
                 &s,
@@ -199,7 +434,7 @@ fn test_decode_data() {
     decoder.next_image().expect("Cannot read image IFD");
     assert_eq!(decoder.colortype().unwrap(), ColorType::RGB(8));
     assert_eq!(decoder.dimensions().unwrap(), (100, 100));
-    if let DecodingResult::U8(img_res) = decoder.read_image().unwrap() {
+    if let DecodingSampleBuffer::U8(img_res) = decoder.read_image().unwrap() {
         assert_eq!(image_data, img_res);
     } else {
         panic!("Wrong data type");
@@ -246,7 +481,8 @@ fn test_inner_access() {
     decoder.next_image().expect("Cannot read image IFD");
     assert_eq!(decoder.colortype().unwrap(), ColorType::RGB(8));
 
-    let c = decoder
+    let mut ifd = decoder.current_ifd();
+    let c = ifd
         .get_tag(tiff::tags::Tag::Compression)
         .unwrap()
         .into_u16()
@@ -255,13 +491,13 @@ fn test_inner_access() {
 
     // Because the image is uncompressed, reading the first tile directly with the inner reader
     // should yield the same result as reading it with the decoder's read_chunk method.
-    let first_offset = decoder
+    let first_offset = ifd
         .get_tag_u32_vec(tiff::tags::Tag::TileOffsets)
         .unwrap()
         .into_iter()
         .next()
         .unwrap();
-    let first_byte_count = decoder
+    let first_byte_count = ifd
         .get_tag_u32_vec(tiff::tags::Tag::TileByteCounts)
         .unwrap()
         .into_iter()
@@ -279,7 +515,7 @@ fn test_inner_access() {
     let raw_sum: u64 = buf.into_iter().map(<u64>::from).sum();
 
     match decoder.read_chunk(0).unwrap() {
-        DecodingResult::U8(chunk) => {
+        DecodingSampleBuffer::U8(chunk) => {
             let sum: u64 = chunk.into_iter().map(<u64>::from).sum();
             assert_eq!(sum, raw_sum);
         }
@@ -338,7 +574,7 @@ fn test_tiled_incremental() {
 
     for tile in 0..tiles {
         match decoder.read_chunk(tile).unwrap() {
-            DecodingResult::U8(res) => {
+            DecodingSampleBuffer::U8(res) => {
                 let sum: u64 = res.into_iter().map(<u64>::from).sum();
                 assert_eq!(sum, sums[tile as usize]);
             }
@@ -372,21 +608,21 @@ fn test_read_planar_bands() {
 
     // 1st band (red)
     match decoder.read_chunk(0).unwrap() {
-        DecodingResult::U8(chunk) => {
+        DecodingSampleBuffer::U8(chunk) => {
             assert_eq!(chunk[0], 73);
         }
         _ => panic!("Wrong bit depth"),
     }
     // 2nd band (green)
     match decoder.read_chunk(chunks / 3).unwrap() {
-        DecodingResult::U8(chunk) => {
+        DecodingSampleBuffer::U8(chunk) => {
             assert_eq!(chunk[0], 51);
         }
         _ => panic!("Wrong bit depth"),
     }
     // 3rd band (blue)
     match decoder.read_chunk(chunks / 3 * 2).unwrap() {
-        DecodingResult::U8(chunk) => {
+        DecodingSampleBuffer::U8(chunk) => {
             assert_eq!(chunk[0], 30);
         }
         _ => panic!("Wrong bit depth"),
@@ -762,9 +998,62 @@ fn test_decode_huge_g4() {
         .read_image()
         .expect("failed to decode huge G4 image");
 
-    if let tiff::decoder::DecodingResult::U8(data) = result {
+    if let tiff::decoder::DecodingSampleBuffer::U8(data) = result {
         assert_eq!(data.len(), (width as usize * height as usize));
     } else {
         panic!("Unexpected decoding result type");
     }
 }
+
+// ---- WhiteIsZero tests across bit depths ----
+
+// WhiteIsZero + extended bit depth (12-bit gray, synthetic 4x2 image)
+#[test]
+fn test_gray_u12_white_is_zero() {
+    // Values: [0, 1000, 2000, 4095, 100, 500, 3000, 3500]
+    // After WhiteIsZero inversion: [4095, 3095, 2095, 0, 3995, 3595, 1095, 595]
+    test_image_sum_u16("miniswhite-1c-12b.tiff", ColorType::Gray(12), 18565);
+}
+
+// WhiteIsZero + non-standard sub-byte depths (3-bit and 6-bit, synthetic 8x2 images)
+// These verify per-sample inversion for packed depths where samples cross byte boundaries.
+#[test]
+fn test_gray_u3_white_is_zero() {
+    test_image_sum_u8("miniswhite-1c-3b.tiff", ColorType::Gray(3), 765);
+}
+
+#[test]
+fn test_gray_u6_white_is_zero() {
+    // Values: [0, 10, 20, 30, 40, 50, 60, 63] × 2 rows
+    // After inversion: [63, 53, 43, 33, 23, 13, 3, 0] × 2 rows
+    test_image_sum_u8("miniswhite-1c-6b.tiff", ColorType::Gray(6), 2124);
+}
+
+// ---- Non-standard sub-byte depths (BlackIsZero) ----
+// Verify that odd bit depths (3, 5, 7) decode without error.
+
+#[test]
+fn test_gray_u3() {
+    // 8x2 image, values [0..7, 7..0], packed to 6 bytes
+    test_image_sum_u8("minisblack-1c-3b.tiff", ColorType::Gray(3), 765);
+}
+
+#[test]
+fn test_gray_u5() {
+    // 8x2 image, packed to 10 bytes
+    test_image_sum_u8("minisblack-1c-5b.tiff", ColorType::Gray(5), 1275);
+}
+
+#[test]
+fn test_gray_u7() {
+    // 8x2 image, packed to 14 bytes
+    test_image_sum_u8("minisblack-1c-7b.tiff", ColorType::Gray(7), 1711);
+}
+
+// ---- Horizontal predictor + extended bit depth ----
+
+#[test]
+fn test_gray_u12_hpredict() {
+    // Delta-encoded 12-bit values: [100, 200, 300, 400, 1000, 2000, 3000, 4000]
+    test_image_sum_u16("hpredict-1c-12b.tiff", ColorType::Gray(12), 11000);
+}

tests/decode_libtiffpic.rs

@@ -1,7 +1,9 @@
 use std::collections::HashMap;
 use std::{fs::File, path};
 
-use tiff::decoder::{Decoder, DecodingResult};
+use tiff::decoder::{Decoder, DecodingSampleBuffer};
+use tiff::tags::{ByteOrder, Type};
+use tiff::ColorType;
 
 use libtest_mimic::{Arguments, Failed, Trial};
 use walkdir::WalkDir;
@@ -9,99 +11,202 @@ use walkdir::WalkDir;
 const REFERENCE_DIR: &str = "tests/libtiffpic";
 
 // `find test/libtiffpic -type f | sort`
-const FILES: &[(&str, bool)] = &[
-    ("tests/libtiffpic/caspian.tif", true),
-    ("tests/libtiffpic/cramps.tif", true),
-    // FIXME: See <https://github.com/image-rs/image-tiff/issues/338>, this has tiles as
-    // StripOffsets and has a RowsPerStrip.
-    ("tests/libtiffpic/cramps-tile.tif", false),
-    ("tests/libtiffpic/CVS/Entries", false),
-    ("tests/libtiffpic/CVS/Repository", false),
-    ("tests/libtiffpic/CVS/Root", false),
-    ("tests/libtiffpic/depth/CVS/Entries", false),
-    ("tests/libtiffpic/depth/CVS/Repository", false),
-    ("tests/libtiffpic/depth/CVS/Root", false),
-    ("tests/libtiffpic/depth/flower-minisblack-02.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-04.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-06.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-08.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-10.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-12.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-14.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-16.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-24.tif", true),
-    ("tests/libtiffpic/depth/flower-minisblack-32.tif", true),
-    ("tests/libtiffpic/depth/flower-palette-02.tif", true),
-    ("tests/libtiffpic/depth/flower-palette-04.tif", true),
-    ("tests/libtiffpic/depth/flower-palette-08.tif", true),
-    ("tests/libtiffpic/depth/flower-palette-16.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-02.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-04.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-08.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-10.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-12.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-14.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-16.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-24.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-contig-32.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-02.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-04.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-08.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-10.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-12.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-14.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-16.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-24.tif", true),
-    ("tests/libtiffpic/depth/flower-rgb-planar-32.tif", true),
+//
+// Each entry maps a file path to its expected behavior:
+//   None           = not a TIFF file, skip entirely
+//   Some(0)        = TIFF with unsupported features, decode-only smoke test
+//   Some(nonzero)  = TIFF with full CRC32 hash verification of decoded output
+const FILES: &[(&str, Option<u32>)] = &[
+    ("tests/libtiffpic/caspian.tif", Some(0x4ea8d4e4)),
+    ("tests/libtiffpic/cramps.tif", Some(0xdfa2fba4)),
+    ("tests/libtiffpic/cramps-tile.tif", Some(0xdfa2fba4)),
+    ("tests/libtiffpic/CVS/Entries", None),
+    ("tests/libtiffpic/CVS/Repository", None),
+    ("tests/libtiffpic/CVS/Root", None),
+    ("tests/libtiffpic/depth/CVS/Entries", None),
+    ("tests/libtiffpic/depth/CVS/Repository", None),
+    ("tests/libtiffpic/depth/CVS/Root", None),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-02.tif",
+        Some(0x1c90f515),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-04.tif",
+        Some(0x0f4813cb),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-06.tif",
+        Some(0xf0c0a901),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-08.tif",
+        Some(0xe797b15b),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-10.tif",
+        Some(0xdee442ec),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-12.tif",
+        Some(0x4810c4e9),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-14.tif",
+        Some(0x7e03cf03),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-16.tif",
+        Some(0x8e0add32),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-24.tif",
+        Some(0x5cf29313),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-minisblack-32.tif",
+        Some(0x80025eee),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-palette-02.tif",
+        Some(0xaeb21cff),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-palette-04.tif",
+        Some(0x339d428b),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-palette-08.tif",
+        Some(0xb6b203e9),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-palette-16.tif",
+        Some(0x4e02308f),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-02.tif",
+        Some(0x8f16cf35),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-04.tif",
+        Some(0x95e97f94),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-08.tif",
+        Some(0x98134e7c),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-10.tif",
+        Some(0xa2ad8f4d),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-12.tif",
+        Some(0xfad187fc),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-14.tif",
+        Some(0x93fdc170),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-16.tif",
+        Some(0x25e1066b),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-24.tif",
+        Some(0x25cdf743),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-contig-32.tif",
+        Some(0x195dde9c),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-02.tif",
+        Some(0xcc0281ca),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-04.tif",
+        Some(0x867134b2),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-08.tif",
+        Some(0x2341af83),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-10.tif",
+        Some(0x79211047),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-12.tif",
+        Some(0x14a0ff72),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-14.tif",
+        Some(0xc077389d),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-16.tif",
+        Some(0xd0849282),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-24.tif",
+        Some(0x433d333b),
+    ),
+    (
+        "tests/libtiffpic/depth/flower-rgb-planar-32.tif",
+        Some(0xd0780b23),
+    ),
     (
         "tests/libtiffpic/depth/flower-separated-contig-08.tif",
-        true,
+        Some(0x97fb03a6),
     ),
     (
         "tests/libtiffpic/depth/flower-separated-contig-16.tif",
-        true,
+        Some(0xb6ee0135),
     ),
     (
         "tests/libtiffpic/depth/flower-separated-planar-08.tif",
-        true,
+        Some(0x502e93fa),
     ),
     (
         "tests/libtiffpic/depth/flower-separated-planar-16.tif",
-        true,
+        Some(0x50e580d9),
     ),
-    ("tests/libtiffpic/depth/genimages", false),
-    ("tests/libtiffpic/depth/README.txt", false),
-    ("tests/libtiffpic/depth/summary.txt", false),
-    ("tests/libtiffpic/dscf0013.tif", true),
-    ("tests/libtiffpic/fax2d.tif", true),
+    ("tests/libtiffpic/depth/genimages", None),
+    ("tests/libtiffpic/depth/README.txt", None),
+    ("tests/libtiffpic/depth/summary.txt", None),
+    ("tests/libtiffpic/dscf0013.tif", Some(0)), // unsupported YCbCr chroma subsampling
+    ("tests/libtiffpic/fax2d.tif", Some(0xc2f30c6f)),
     // No support for direct CCITT Group 3 1D format
-    ("tests/libtiffpic/g3test.g3", false),
-    ("tests/libtiffpic/g3test.tif", true),
-    ("tests/libtiffpic/jello.tif", true),
-    ("tests/libtiffpic/jim___ah.tif", true),
-    ("tests/libtiffpic/jim___cg.tif", true),
-    ("tests/libtiffpic/jim___dg.tif", true),
-    ("tests/libtiffpic/jim___gg.tif", true),
-    ("tests/libtiffpic/ladoga.tif", true),
-    ("tests/libtiffpic/off_l16.tif", true),
-    ("tests/libtiffpic/off_luv24.tif", true),
-    ("tests/libtiffpic/off_luv32.tif", true),
-    ("tests/libtiffpic/oxford.tif", true),
-    ("tests/libtiffpic/pc260001.tif", true),
-    ("tests/libtiffpic/quad-jpeg.tif", true),
-    ("tests/libtiffpic/quad-lzw.tif", true),
-    // FIXME: See <https://github.com/image-rs/image-tiff/issues/338>, this has tiles as
-    // StripOffsets and has a RowsPerStrip.
-    ("tests/libtiffpic/quad-tile.tif", false),
-    ("tests/libtiffpic/README", false),
-    ("tests/libtiffpic/smallliz.tif", true),
-    ("tests/libtiffpic/strike.tif", true),
-    ("tests/libtiffpic/text.tif", true),
-    ("tests/libtiffpic/ycbcr-cat.tif", true),
-    ("tests/libtiffpic/zackthecat.tif", true),
+    ("tests/libtiffpic/g3test.g3", None),
+    ("tests/libtiffpic/g3test.tif", Some(0x304b606b)),
+    ("tests/libtiffpic/jello.tif", Some(0xb03dbda9)),
+    ("tests/libtiffpic/jim___ah.tif", Some(0x81a27b7f)),
+    ("tests/libtiffpic/jim___cg.tif", Some(0xfd31747c)),
+    ("tests/libtiffpic/jim___dg.tif", Some(0x8c6a5e8f)),
+    ("tests/libtiffpic/jim___gg.tif", Some(0x8c6a5e8f)),
+    ("tests/libtiffpic/ladoga.tif", Some(0x9b118511)),
+    ("tests/libtiffpic/off_l16.tif", Some(0)), // LogLuv decoder output varies across platforms
+    ("tests/libtiffpic/off_luv24.tif", Some(0x2bee71a2)),
+    ("tests/libtiffpic/off_luv32.tif", Some(0)), // LogLuv decoder output varies across platforms
+    ("tests/libtiffpic/oxford.tif", Some(0x355d2e3e)),
+    ("tests/libtiffpic/pc260001.tif", Some(0xdb56b753)),
+    ("tests/libtiffpic/quad-jpeg.tif", Some(0xcba22475)),
+    ("tests/libtiffpic/quad-lzw.tif", Some(0)), // invalid LZW stream
+    ("tests/libtiffpic/quad-tile.tif", Some(0x6055f9ee)),
+    ("tests/libtiffpic/README", None),
+    ("tests/libtiffpic/smallliz.tif", Some(0)), // unsupported YCbCr chroma subsampling
+    ("tests/libtiffpic/strike.tif", Some(0x016b0f6a)),
+    ("tests/libtiffpic/text.tif", Some(0)), // unsupported compression
+    ("tests/libtiffpic/ycbcr-cat.tif", Some(0)), // unsupported YCbCr chroma subsampling
+    ("tests/libtiffpic/zackthecat.tif", Some(0)), // unsupported YCbCr chroma subsampling
 ];
 
 fn main() {
+    let args: Vec<String> = std::env::args().collect();
+    if args.iter().any(|a| a == "--print-hashes") {
+        print_reference_hashes();
+        return;
+    }
+
     let mut candidates: HashMap<_, _> = FILES.iter().copied().collect();
     let mut trials = Vec::new();
 
@@ -118,22 +223,19 @@ fn main() {
         let path = path.replace(std::path::MAIN_SEPARATOR, "/"); // always use UNIX path separators
 
         // Mark this path as consumed in either case by removing it.
-        let Some(should_decode) = candidates.remove(path.as_str()) else {
+        let Some(expected_hash) = candidates.remove(path.as_str()) else {
             panic!("File {} not in reference list", path);
         };
 
-        // Check if we should turn it into a test case.
-        if !should_decode {
+        // None = non-image file, skip
+        let Some(expected_hash) = expected_hash else {
             continue;
-        }
+        };
 
         let path = path.to_string();
         trials.push(Trial::test(
             path.to_string(),
-            move || -> Result<(), Failed> {
-                decode_libtiffpic(&path)
-                    .map_err(|e| Failed::from(format_args!("Decoding failed for {}: {}", path, e)))
-            },
+            move || -> Result<(), Failed> { decode_and_verify(&path, expected_hash) },
         ));
     }
 
@@ -149,17 +251,114 @@ fn main() {
     libtest_mimic::run(&args, trials).exit();
 }
 
-fn decode_libtiffpic(path: &str) -> Result<(), tiff::TiffError> {
-    let path = path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(path);
+/// Map DecodingResult variant to a TIFF Type for byte-order normalization.
+fn sample_type_of(result: &DecodingSampleBuffer) -> Type {
+    match result {
+        DecodingSampleBuffer::U8(_) => Type::BYTE,
+        DecodingSampleBuffer::I8(_) => Type::SBYTE,
+        DecodingSampleBuffer::U16(_) => Type::SHORT,
+        DecodingSampleBuffer::I16(_) => Type::SSHORT,
+        DecodingSampleBuffer::U32(_) => Type::LONG,
+        DecodingSampleBuffer::I32(_) => Type::SLONG,
+        DecodingSampleBuffer::F32(_) => Type::FLOAT,
+        DecodingSampleBuffer::U64(_) => Type::LONG8,
+        DecodingSampleBuffer::I64(_) => Type::SLONG8,
+        DecodingSampleBuffer::F64(_) => Type::DOUBLE,
+        DecodingSampleBuffer::F16(_) => Type::SHORT, // f16 is 2 bytes like SHORT
+    }
+}
 
+/// Hash color type into the hasher (discriminant + fields).
+fn hash_color_type(hasher: &mut crc32fast::Hasher, color_type: ColorType) {
+    match color_type {
+        ColorType::Gray(n) => hasher.update(&[0, n]),
+        ColorType::RGB(n) => hasher.update(&[1, n]),
+        ColorType::Palette(n) => hasher.update(&[2, n]),
+        ColorType::GrayA(n) => hasher.update(&[3, n]),
+        ColorType::RGBA(n) => hasher.update(&[4, n]),
+        ColorType::CMYK(n) => hasher.update(&[5, n]),
+        ColorType::CMYKA(n) => hasher.update(&[6, n]),
+        ColorType::YCbCr(n) => hasher.update(&[7, n]),
+        ColorType::Lab(n) => hasher.update(&[8, n]),
+        ColorType::Multiband {
+            bit_depth,
+            num_samples,
+        } => {
+            hasher.update(&[9, bit_depth]);
+            hasher.update(&num_samples.to_le_bytes());
+        }
+        other => panic!("compute_tiff_hash: unhandled ColorType {other:?}"),
+    }
+}
+
+/// Compute a CRC32 hash of the full decoded TIFF output using read_image_to_buffer.
+///
+/// Hashes per page: page index, dimensions, color type, TIFF sample type tag,
+/// and decoded sample data normalized to little-endian byte order.
+fn compute_hash(path: &std::path::Path) -> Result<u32, tiff::TiffError> {
     let img_file = File::open(path)?;
     let mut decoder = Decoder::open(img_file)?;
+    let mut hasher = crc32fast::Hasher::new();
+    let mut buffer = DecodingSampleBuffer::U8(vec![]);
 
-    let mut buffer = DecodingResult::U8(vec![]);
+    let mut page = 0u32;
     while decoder.more_images() {
         decoder.next_image()?;
-        let _layout = decoder.read_image_to_buffer(&mut buffer);
+        let (width, height) = decoder.dimensions()?;
+        let color_type = decoder.colortype()?;
+        let _layout = decoder.read_image_to_buffer(&mut buffer)?;
+
+        hasher.update(&page.to_le_bytes());
+        hasher.update(&width.to_le_bytes());
+        hasher.update(&height.to_le_bytes());
+        hash_color_type(&mut hasher, color_type);
+
+        let sample_type = sample_type_of(&buffer);
+        hasher.update(&sample_type.to_u16().to_le_bytes());
+
+        let mut buf = buffer.as_buffer(0);
+        let bytes = buf.as_bytes_mut();
+        ByteOrder::native().convert(sample_type, bytes, ByteOrder::LittleEndian);
+        hasher.update(bytes);
+
+        page += 1;
+    }
+
+    hasher.update(&page.to_le_bytes());
+    Ok(hasher.finalize())
+}
+
+fn decode_and_verify(path: &str, expected_hash: u32) -> Result<(), Failed> {
+    let full_path = path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(path);
+
+    if expected_hash == 0 {
+        // Smoke test: try to decode, tolerate errors (unsupported formats)
+        let _ = compute_hash(&full_path);
+        return Ok(());
+    }
+
+    let actual_hash = compute_hash(&full_path)
+        .map_err(|e| Failed::from(format!("Decoding failed for {path}: {e}")))?;
+
+    if actual_hash != expected_hash {
+        return Err(Failed::from(format!(
+            "{path}: expected hash 0x{expected_hash:08x} but got 0x{actual_hash:08x}"
+        )));
     }
 
     Ok(())
 }
+
+/// Print reference hashes for all decodable files (use --print-hashes).
+fn print_reference_hashes() {
+    for &(path, expected) in FILES {
+        if expected.is_none() {
+            continue;
+        }
+        let full_path = path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(path);
+        match compute_hash(&full_path) {
+            Ok(hash) => eprintln!("(\"{path}\", Some(0x{hash:08x})),"),
+            Err(e) => eprintln!("// {path}: FAILED: {e}"),
+        }
+    }
+}

tests/decode_planes.rs

@@ -1,4 +1,4 @@
-use tiff::decoder::{Decoder, DecodingResult, Limits, TiffCodingUnit};
+use tiff::decoder::{Decoder, DecodingSampleBuffer, Limits, TiffCodingUnit};
 
 use std::fs::File;
 use std::path::PathBuf;
@@ -84,7 +84,7 @@ fn read_planes_by_limits() {
     let io = std::io::BufReader::new(file);
 
     let mut limits = Limits::default();
-    let mut buffer = DecodingResult::U8(vec![]);
+    let mut buffer = DecodingSampleBuffer::U8(vec![]);
 
     // Make room for 1 plane.
     let mut tif = Decoder::open(io).unwrap();

tests/encode_images.rs

@@ -1,6 +1,6 @@
 extern crate tiff;
 
-use tiff::decoder::{ifd, Decoder, DecodingResult};
+use tiff::decoder::{ifd, Decoder, DecodingSampleBuffer};
 use tiff::encoder::{colortype, Ifd, Ifd8, Predictor, SRational, TiffEncoder};
 use tiff::tags::Tag;
 use tiff::ColorType;
@@ -40,6 +40,7 @@ fn encode_decode() {
         assert_eq!(decoder.dimensions().unwrap(), (100, 100));
 
         let mut all_tags = decoder
+            .current_ifd()
             .tag_iter()
             .filter_map(Result::ok)
             .collect::<Vec<_>>();
@@ -80,13 +81,13 @@ fn encode_decode() {
         );
 
         assert_eq!(
-            decoder.get_tag(Tag::Artist).unwrap(),
+            decoder.current_ifd().get_tag(Tag::Artist).unwrap(),
             ifd::Value::Ascii("Image-tiff".into())
         );
 
-        let mut buffer = tiff::decoder::DecodingResult::U8(vec![]);
+        let mut buffer = tiff::decoder::DecodingSampleBuffer::U8(vec![]);
         let _layout = decoder.read_image_to_buffer(&mut buffer).unwrap();
-        if let tiff::decoder::DecodingResult::U8(img_res) = buffer {
+        if let tiff::decoder::DecodingSampleBuffer::U8(img_res) = buffer {
             assert_eq!(image_data, img_res);
         } else {
             panic!("Wrong data type");
@@ -125,6 +126,7 @@ fn encode_decode_big() {
         assert_eq!(decoder.dimensions().unwrap(), (100, 100));
 
         let mut all_tags = decoder
+            .current_ifd()
             .tag_iter()
             .filter_map(Result::ok)
             .collect::<Vec<_>>();
@@ -165,12 +167,12 @@ fn encode_decode_big() {
         );
 
         assert_eq!(
-            decoder.get_tag(Tag::Artist).unwrap(),
+            decoder.current_ifd().get_tag(Tag::Artist).unwrap(),
             ifd::Value::Ascii("Image-tiff".into())
         );
-        let mut buffer = tiff::decoder::DecodingResult::U8(vec![]);
+        let mut buffer = tiff::decoder::DecodingSampleBuffer::U8(vec![]);
         let _layout = decoder.read_image_to_buffer(&mut buffer).unwrap();
-        if let DecodingResult::U8(img_res) = buffer {
+        if let DecodingSampleBuffer::U8(img_res) = buffer {
             assert_eq!(image_data, img_res);
         } else {
             panic!("Wrong data type");
@@ -258,11 +260,11 @@ macro_rules! test_roundtrip {
 
             assert_eq!(decoder.colortype().unwrap(), expected_type);
 
-            let mut buffer = tiff::decoder::DecodingResult::U8(vec![]);
+            let mut buffer = tiff::decoder::DecodingSampleBuffer::U8(vec![]);
             decoder.read_image_to_buffer(&mut buffer).unwrap();
 
             let image_data = match buffer {
-                DecodingResult::$buffer(res) => res,
+                DecodingSampleBuffer::$buffer(res) => res,
                 _ => panic!("Wrong data type"),
             };
 
@@ -275,11 +277,11 @@ macro_rules! test_roundtrip {
             }
             file.seek(SeekFrom::Start(0)).unwrap();
             {
-                let mut buffer = tiff::decoder::DecodingResult::U8(vec![]);
+                let mut buffer = tiff::decoder::DecodingSampleBuffer::U8(vec![]);
                 let mut decoder = Decoder::open(&mut file).unwrap();
                 decoder.next_image().unwrap();
                 decoder.read_image_to_buffer(&mut buffer).unwrap();
-                if let DecodingResult::$buffer(img_res) = buffer {
+                if let DecodingSampleBuffer::$buffer(img_res) = buffer {
                     assert_eq!(*image_data, img_res);
                 } else {
                     panic!("Wrong data type");
@@ -418,9 +420,9 @@ fn test_gray_f32_floating_point_predictor() {
         decoder.next_image().unwrap();
         assert_eq!(decoder.colortype().unwrap(), ColorType::Gray(32));
 
-        let mut buffer = DecodingResult::F32(vec![]);
+        let mut buffer = DecodingSampleBuffer::F32(vec![]);
         decoder.read_image_to_buffer(&mut buffer).unwrap();
-        if let DecodingResult::F32(img_res) = buffer {
+        if let DecodingSampleBuffer::F32(img_res) = buffer {
             assert_eq!(image_data.len(), img_res.len());
             for (orig, decoded) in image_data.iter().zip(img_res.iter()) {
                 assert_eq!(
@@ -465,9 +467,9 @@ fn test_rgb_f32_floating_point_predictor() {
         decoder.next_image().unwrap();
         assert_eq!(decoder.colortype().unwrap(), ColorType::RGB(32));
 
-        let mut buffer = DecodingResult::F32(vec![]);
+        let mut buffer = DecodingSampleBuffer::F32(vec![]);
         decoder.read_image_to_buffer(&mut buffer).unwrap();
-        if let DecodingResult::F32(img_res) = buffer {
+        if let DecodingSampleBuffer::F32(img_res) = buffer {
             assert_eq!(image_data.len(), img_res.len());
             for (i, (orig, decoded)) in image_data.iter().zip(img_res.iter()).enumerate() {
                 assert_eq!(
@@ -509,9 +511,9 @@ fn test_gray_f64_floating_point_predictor() {
         decoder.next_image().unwrap();
         assert_eq!(decoder.colortype().unwrap(), ColorType::Gray(64));
 
-        let mut buffer = DecodingResult::F64(vec![]);
+        let mut buffer = DecodingSampleBuffer::F64(vec![]);
         decoder.read_image_to_buffer(&mut buffer).unwrap();
-        if let DecodingResult::F64(img_res) = buffer {
+        if let DecodingSampleBuffer::F64(img_res) = buffer {
             assert_eq!(image_data.len(), img_res.len());
             for (orig, decoded) in image_data.iter().zip(img_res.iter()) {
                 assert_eq!(
@@ -539,37 +541,57 @@ trait AssertDecode {
 
 impl<R: std::io::Read + std::io::Seek> AssertDecode for Decoder<R> {
     fn assert_tag_u32(&mut self, tag: u16) -> u32 {
-        self.get_tag(Tag::Unknown(tag)).unwrap().into_u32().unwrap()
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
+            .unwrap()
+            .into_u32()
+            .unwrap()
     }
     fn assert_tag_u32_vec(&mut self, tag: u16) -> Vec<u32> {
-        self.get_tag(Tag::Unknown(tag))
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
             .unwrap()
             .into_u32_vec()
             .unwrap()
     }
     fn assert_tag_i32(&mut self, tag: u16) -> i32 {
-        self.get_tag(Tag::Unknown(tag)).unwrap().into_i32().unwrap()
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
+            .unwrap()
+            .into_i32()
+            .unwrap()
     }
     fn assert_tag_i32_vec(&mut self, tag: u16) -> Vec<i32> {
-        self.get_tag(Tag::Unknown(tag))
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
             .unwrap()
             .into_i32_vec()
             .unwrap()
     }
     fn assert_tag_u64(&mut self, tag: u16) -> u64 {
-        self.get_tag(Tag::Unknown(tag)).unwrap().into_u64().unwrap()
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
+            .unwrap()
+            .into_u64()
+            .unwrap()
     }
     fn assert_tag_u64_vec(&mut self, tag: u16) -> Vec<u64> {
-        self.get_tag(Tag::Unknown(tag))
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
             .unwrap()
             .into_u64_vec()
             .unwrap()
     }
     fn assert_tag_i64(&mut self, tag: u16) -> i64 {
-        self.get_tag(Tag::Unknown(tag)).unwrap().into_i64().unwrap()
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
+            .unwrap()
+            .into_i64()
+            .unwrap()
     }
     fn assert_tag_i64_vec(&mut self, tag: u16) -> Vec<i64> {
-        self.get_tag(Tag::Unknown(tag))
+        self.current_ifd()
+            .get_tag(Tag::Unknown(tag))
             .unwrap()
             .into_i64_vec()
             .unwrap()
@@ -776,13 +798,19 @@ fn test_rows_per_strip() {
     {
         let mut decoder = Decoder::open(&mut file).unwrap();
         decoder.next_image().unwrap();
-        assert_eq!(decoder.get_tag_u64(Tag::RowsPerStrip).unwrap(), 2);
+        assert_eq!(
+            decoder
+                .current_ifd()
+                .get_tag_u64(Tag::RowsPerStrip)
+                .unwrap(),
+            2
+        );
         assert_eq!(decoder.strip_count().unwrap(), 50);
 
         for i in 0..50 {
             let img2 = [i; 2 * 100];
             match decoder.read_chunk(i as u32).unwrap() {
-                DecodingResult::U8(data) => assert_eq!(&img2[..], &data[..]),
+                DecodingSampleBuffer::U8(data) => assert_eq!(&img2[..], &data[..]),
                 other => panic!("Incorrect strip type {other:?}"),
             }
         }
@@ -829,6 +857,7 @@ fn test_auxiliary_directory() {
         let _ = decoder.read_image().unwrap();
 
         let exif_location = decoder
+            .current_ifd()
             .get_tag(Tag::ExifDirectory)
             .expect("second directory missing Exif")
             .into_ifd_pointer()

tests/encode_images_with_compression.rs

@@ -2,10 +2,9 @@ extern crate tiff;
 
 use std::io::{Cursor, Seek, Write};
 use tiff::{
-    decoder::{Decoder, DecodingResult},
+    decoder::{Decoder, DecodingSampleBuffer},
     encoder::{
         colortype::{self, ColorType},
-        compression::*,
         Compression, TiffEncoder, TiffValue,
     },
 };
@@ -116,7 +115,7 @@ fn encode_decode_with_compression(compression: Compression) {
         // Check the RGB image
         assert_eq!(
             match decoder.read_image() {
-                Ok(DecodingResult::U16(image_data)) => image_data,
+                Ok(DecodingSampleBuffer::U16(image_data)) => image_data,
                 unexpected => panic!("Descoding RGB failed: {unexpected:?}"),
             },
             image_rgb.reference_data()
@@ -126,7 +125,7 @@ fn encode_decode_with_compression(compression: Compression) {
         decoder.next_image().unwrap();
         assert_eq!(
             match decoder.read_image() {
-                Ok(DecodingResult::U8(image_data)) => image_data,
+                Ok(DecodingSampleBuffer::U8(image_data)) => image_data,
                 unexpected => panic!("Decoding grayscale failed: {unexpected:?}"),
             },
             image_grayscale.reference_data()
@@ -148,9 +147,9 @@ fn encode_decode_with_lzw() {
 #[test]
 #[cfg(feature = "deflate")]
 fn encode_decode_with_deflate() {
-    encode_decode_with_compression(Compression::Deflate(DeflateLevel::Fast));
-    encode_decode_with_compression(Compression::Deflate(DeflateLevel::Balanced));
-    encode_decode_with_compression(Compression::Deflate(DeflateLevel::Best));
+    encode_decode_with_compression(Compression::Deflate(1));
+    encode_decode_with_compression(Compression::Deflate(6));
+    encode_decode_with_compression(Compression::Deflate(9));
 }
 
 #[test]