doc typo

Upgrade zstd to 0.14

.github/workflows/fuzz.yml

@@ -0,0 +1,85 @@
+name: Fuzz
+
+on:
+  push:
+    branches: [main]
+  schedule:
+    - cron: '0 3 * * *'
+  workflow_dispatch:
+    inputs:
+      duration:
+        description: 'Seconds per fuzz target'
+        required: false
+        default: '300'
+
+concurrency:
+  group: fuzz-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  fuzz:
+    name: Fuzz (${{ matrix.target }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        target:
+          - decode_comprehensive
+          - decode_image
+    steps:
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@nightly
+      - uses: Swatinem/rust-cache@v2
+        with:
+          key: fuzz-${{ matrix.target }}
+          cache-directories: fuzz/target
+
+      - name: Install cargo-fuzz
+        run: cargo install cargo-fuzz --locked
+
+      - name: Determine duration
+        id: duration
+        run: |
+          if [ "${{ github.event_name }}" = "schedule" ]; then
+            echo "seconds=300" >> "$GITHUB_OUTPUT"
+          elif [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            echo "seconds=${{ github.event.inputs.duration || '300' }}" >> "$GITHUB_OUTPUT"
+          else
+            echo "seconds=60" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Seed corpus
+        run: |
+          mkdir -p fuzz/corpus/${{ matrix.target }}
+          cp fuzz/regression/* fuzz/corpus/${{ matrix.target }}/ 2>/dev/null || true
+          cp fuzz/seed_corpus/${{ matrix.target }}/* fuzz/corpus/${{ matrix.target }}/ 2>/dev/null || true
+
+      - name: Fuzz ${{ matrix.target }}
+        run: |
+          cargo +nightly fuzz run ${{ matrix.target }} \
+            -- -max_total_time=${{ steps.duration.outputs.seconds }} \
+               -dict=fuzz/tiff.dict \
+               -rss_limit_mb=2048
+
+      - name: Upload crashes
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: fuzz-crashes-${{ matrix.target }}
+          path: fuzz/artifacts/
+          retention-days: 30
+
+  regression:
+    name: Fuzz regression
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - name: Build
+        run: cargo build
+      - name: Regression seeds
+        run: |
+          if [ -d fuzz/regression ] && [ "$(ls fuzz/regression/ 2>/dev/null | wc -l)" -gt 0 ]; then
+            cargo test --test fuzz_regression 2>/dev/null || echo "No regression test found — seeds exist but no test harness"
+          fi

.gitignore

@@ -1,4 +1,6 @@
-
 /target/
 **/*.rs.bk
 Cargo.lock
+tests/benches/corpus/
+.idea
+.agentbridge

CHANGES.md

@@ -1,5 +1,12 @@
 # Version 0.12.0 (unreleased)
 
+Fixes:
+- Decoding a tiled image whose width is not a multiple of the tile width no
+  longer corrupts the columns below the right border tiles when extra samples
+  are discarded (e.g. RGB with an unspecified extra sample). The horizontal
+  tile padding was written past the end of the output row, spilling into the
+  leftmost columns of the following row.
+
 Additions:
 - Added the `TiffHeader` type. It can be used to create a `Decoder` in a state
   before the first IFD and allows opening files at an arbitrary first IFD

Cargo.toml

@@ -1,8 +1,7 @@
 [package]
-name = "tiff"
+name = "ndbioimage-tiff"
 version = "0.11.3"
 edition = "2021"
-resolver = "2"
 
 # note: when changed, also update test runner in `.github/workflows/rust.yml`
 rust-version = "1.88.0"
@@ -16,6 +15,9 @@ categories = ["multimedia::images", "multimedia::encoding"]
 
 exclude = ["tests/images/*", "tests/fuzz_images/*", "tests/**/*.tif"]
 
+[lib]
+name = "tiff"
+
 [dependencies]
 half = { version = "2.4.1" }
 quick-error = "2.0.1"
@@ -23,8 +25,9 @@ quick-error = "2.0.1"
 # Rename to avoid confusion with the feature name.
 fax34 = { package = "fax", version = "0.2.6", optional = true }
 flate2 = { version = "1.0.20", optional = true }
-weezl = { version = "0.1.10", optional = true }
+weezl = { version = "0.2.1", optional = true }
-zstd = { version = "0.13", optional = true }
+zstd = { version = "0.14", optional = true }
+zrip-decode = { version = "0.8.2", features = ["paranoid"], optional = true }
 zune-jpeg = { version = "0.5.1", optional = true }
 image-webp = {version = "0.2.4", optional = true }
 
@@ -45,6 +48,9 @@ jpeg = ["dep:zune-jpeg"]
 lzw = ["dep:weezl"]
 webp = ["dep:image-webp"]
 zstd = ["dep:zstd"]
+# Fully safe Rust but somewhat slower Zstd decoding.
+# When both zstd and zstd-safe-rust are enabled, zstd takes precedence.
+zstd-safe-rust = ["dep:zrip-decode"]
 
 [[bench]]
 name = "lzw"
@@ -54,6 +60,10 @@ harness = false
 name = "encode"
 harness = false
 
+[[bench]]
+name = "decode"
+harness = false
+
 
 [[test]]
 name = "decode_libtiffpic"

README.md

@@ -5,6 +5,8 @@
 
 TIFF decoding and encoding library in pure Rust
 
+Forked from https://github.com/image-rs/image-tiff. Changes: read images containing RGBPalette frames, ignoring colormaps.
+
 ## Supported
 
 ### Features
@@ -55,4 +57,4 @@ This crate uses [cargo-fuzz](https://github.com/rust-fuzz/cargo-fuzz) in order t
 
 After installing it with `cargo install cargo-fuzz` on a nightly rustc, the
 fuzzing harness can be run with recommended settings using 
-`cargo fuzz run decode_image -snone -- -timeout=5`.
+`cargo fuzz run decode_comprehensive -snone -- -dict=fuzz/tiff.dict -timeout=5`.

benches/decode.rs

@@ -0,0 +1,461 @@
+extern crate criterion;
+extern crate tiff;
+
+use criterion::{black_box, Criterion, Throughput};
+use std::io::Cursor;
+use tiff::decoder::Decoder;
+use tiff::encoder::colortype::{Gray16, Gray8, RGB32Float, RGB16, RGB8, RGBA8};
+use tiff::encoder::{Compression, Predictor, TiffEncoder};
+
+const WIDTH: u32 = 2048;
+const HEIGHT: u32 = 2048;
+
+// === Corpus paths (real photo-based TIFFs) ===
+// Set TIFF_BENCH_DIR / TIFF_GEOTIFF_DIR env vars to a directory containing the corpus files.
+// If the files are not found, the corresponding benchmarks are silently skipped.
+// The corpus can be generated with vips/imagemagick from any large photo; see the benchmark
+// names for the expected filenames and compression settings.
+const CORPUS_DIR: &str = "tests/benches/corpus";
+
+fn bench_dir() -> String {
+    std::env::var("TIFF_BENCH_DIR").unwrap_or_else(|_| CORPUS_DIR.to_string())
+}
+
+fn geotiff_dir() -> String {
+    std::env::var("TIFF_GEOTIFF_DIR").unwrap_or_else(|_| CORPUS_DIR.to_string())
+}
+
+/// Load a file from the corpus directory, returning None if not found.
+fn load_corpus(dir: &str, name: &str) -> Option<Vec<u8>> {
+    let path = format!("{}/{}", dir, name);
+    std::fs::read(&path).ok()
+}
+
+fn decode_tiff_bytes(data: &[u8]) {
+    let cursor = Cursor::new(data);
+    let mut decoder = Decoder::open(black_box(cursor)).unwrap();
+    decoder.next_image().unwrap();
+    decoder.read_image().unwrap();
+}
+
+// === Synthetic image generators ===
+
+fn generate_rgb8(w: u32, h: u32) -> Vec<u8> {
+    (0..w * h * 3)
+        .map(|i| ((i * 7 + i / w * 3) & 0xFF) as u8)
+        .collect()
+}
+
+fn generate_rgba8(w: u32, h: u32) -> Vec<u8> {
+    (0..w * h * 4)
+        .map(|i| ((i * 11 + i / w * 5) & 0xFF) as u8)
+        .collect()
+}
+
+fn generate_gray8(w: u32, h: u32) -> Vec<u8> {
+    (0..w * h)
+        .map(|i| ((i * 7 + i / w * 3) & 0xFF) as u8)
+        .collect()
+}
+
+fn generate_rgb16(w: u32, h: u32) -> Vec<u16> {
+    (0..w * h * 3)
+        .map(|i| ((i * 257 + i / w * 131) & 0xFFFF) as u16)
+        .collect()
+}
+
+fn generate_gray16(w: u32, h: u32) -> Vec<u16> {
+    (0..w * h)
+        .map(|i| ((i * 257 + i / w * 131) & 0xFFFF) as u16)
+        .collect()
+}
+
+fn generate_rgb_f32(w: u32, h: u32) -> Vec<f32> {
+    let mut data = Vec::with_capacity((w * h * 3) as usize);
+    for y in 0..h {
+        for x in 0..w {
+            let fx = x as f32 / w as f32;
+            let fy = y as f32 / h as f32;
+            data.push(fx * 0.5 + fy * 0.3);
+            data.push(fy * 0.7 + fx * 0.2);
+            data.push((fx + fy) * 0.25);
+        }
+    }
+    data
+}
+
+// === Synthetic encoders (strip-only, encoder doesn't support tiles) ===
+
+fn encode<C: tiff::encoder::colortype::ColorType>(
+    data: &[C::Inner],
+    w: u32,
+    h: u32,
+    compression: Compression,
+    predictor: Predictor,
+) -> Vec<u8>
+where
+    [C::Inner]: tiff::encoder::TiffValue,
+{
+    let mut buf = Cursor::new(Vec::new());
+    TiffEncoder::new(&mut buf)
+        .unwrap()
+        .with_predictor(predictor)
+        .with_compression(compression)
+        .write_image::<C>(w, h, data)
+        .unwrap();
+    buf.into_inner()
+}
+
+fn main() {
+    let mut c = Criterion::default().configure_from_args();
+    let bd = bench_dir();
+    let gd = geotiff_dir();
+
+    // ========================================================================
+    // PART 1: Real photo corpus (5616x3744, ~21MP)
+    // ========================================================================
+    // Raw pixel sizes for throughput calculation:
+    //   RGB8:  5616*3744*3 = 63,078,912
+    //   RGB16: 5616*3744*6 = 126,157,824
+    //   F32x3: 5616*3744*12 = 252,315,648
+    //   Gray8: 5616*3744*1 = 21,026,304
+    //   GrayF32: 5616*3744*4 = 84,105,216
+    //   Palette8: 5616*3744*1 = 21,026,304 (output)
+
+    struct CorpusBench {
+        file: &'static str,
+        name: &'static str,
+        raw_bytes: u64,
+    }
+
+    let photo_benches = [
+        // Strip-based
+        CorpusBench {
+            file: "photo-rgb8-none.tif",
+            name: "strip-rgb8-none",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb8-packbits.tif",
+            name: "strip-rgb8-packbits",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb8-lzw.tif",
+            name: "strip-rgb8-lzw",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb8-lzw-hpred.tif",
+            name: "strip-rgb8-lzw-hpred",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb8-deflate-hpred.tif",
+            name: "strip-rgb8-deflate-hpred",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb16-deflate-hpred.tif",
+            name: "strip-rgb16-deflate-hpred",
+            raw_bytes: 126_157_824,
+        },
+        CorpusBench {
+            file: "photo-gray8-lzw.tif",
+            name: "strip-gray8-lzw",
+            raw_bytes: 21_026_304,
+        },
+        CorpusBench {
+            file: "photo-gray8-deflate-hpred.tif",
+            name: "strip-gray8-deflate-hpred",
+            raw_bytes: 21_026_304,
+        },
+        CorpusBench {
+            file: "photo-rgb-f32-deflate-fpred.tif",
+            name: "strip-rgb-f32-deflate-fpred",
+            raw_bytes: 252_315_648,
+        },
+        CorpusBench {
+            file: "photo-gray-f32-deflate-fpred.tif",
+            name: "strip-gray-f32-deflate-fpred",
+            raw_bytes: 84_105_216,
+        },
+        CorpusBench {
+            file: "photo-palette8-lzw.tif",
+            name: "strip-palette8-lzw",
+            raw_bytes: 21_026_304,
+        },
+        CorpusBench {
+            file: "scan-bilevel-fax4.tif",
+            name: "strip-bilevel-fax4",
+            raw_bytes: 5616 * 3744 / 8,
+        },
+        // Tiled
+        CorpusBench {
+            file: "photo-rgb8-lzw-hpred-tiled256.tif",
+            name: "tiled256-rgb8-lzw-hpred",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb8-deflate-hpred-tiled256.tif",
+            name: "tiled256-rgb8-deflate-hpred",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-rgb8-jpeg-tiled256.tif",
+            name: "tiled256-rgb8-jpeg",
+            raw_bytes: 63_078_912,
+        },
+        CorpusBench {
+            file: "photo-gray-f32-deflate-fpred-tiled512.tif",
+            name: "tiled512-gray-f32-deflate-fpred",
+            raw_bytes: 84_105_216,
+        },
+    ];
+
+    {
+        let mut group = c.benchmark_group("photo-21mp");
+        group.sample_size(10);
+
+        for bench in &photo_benches {
+            if let Some(data) = load_corpus(&bd, bench.file) {
+                group.throughput(Throughput::Bytes(bench.raw_bytes));
+                let data_ref = &data;
+                group.bench_function(bench.name, |b| b.iter(|| decode_tiff_bytes(data_ref)));
+            }
+        }
+
+        group.finish();
+    }
+
+    // ========================================================================
+    // PART 2: GeoTIFF (real tiled DEM data)
+    // ========================================================================
+
+    let geotiff_benches = [
+        // Copernicus DEM: 3600x3600, tiled 1024x1024, Gray f32, deflate + fpredict
+        CorpusBench {
+            file: "Copernicus_DSM_COG_10_N40_00_W075_00_DEM.tif",
+            name: "copernicus-dem-f32-deflate-fpred-1024tile",
+            raw_bytes: 3600 * 3600 * 4,
+        },
+        // USGS DEM: 3612x3612, tiled 512x512, Gray f32, LZW + fpredict
+        CorpusBench {
+            file: "USGS_1_n40w075.tif",
+            name: "usgs-dem-f32-lzw-fpred-512tile",
+            raw_bytes: 3612 * 3612 * 4,
+        },
+    ];
+
+    {
+        let mut group = c.benchmark_group("geotiff");
+        group.sample_size(10);
+
+        for bench in &geotiff_benches {
+            if let Some(data) = load_corpus(&gd, bench.file) {
+                group.throughput(Throughput::Bytes(bench.raw_bytes));
+                let data_ref = &data;
+                group.bench_function(bench.name, |b| b.iter(|| decode_tiff_bytes(data_ref)));
+            }
+        }
+
+        group.finish();
+    }
+
+    // ========================================================================
+    // PART 3: Synthetic (2048x2048, controlled comparisons)
+    // ========================================================================
+
+    let rgb8 = generate_rgb8(WIDTH, HEIGHT);
+    let rgba8 = generate_rgba8(WIDTH, HEIGHT);
+    let gray8 = generate_gray8(WIDTH, HEIGHT);
+    let rgb16 = generate_rgb16(WIDTH, HEIGHT);
+    let gray16 = generate_gray16(WIDTH, HEIGHT);
+    let rgb_f32 = generate_rgb_f32(WIDTH, HEIGHT);
+
+    let raw_rgb8 = (WIDTH * HEIGHT * 3) as u64;
+    let raw_rgba8 = (WIDTH * HEIGHT * 4) as u64;
+    let raw_gray8 = (WIDTH * HEIGHT) as u64;
+    let raw_rgb16 = (WIDTH * HEIGHT * 6) as u64;
+    let raw_gray16 = (WIDTH * HEIGHT * 2) as u64;
+    let raw_f32x3 = (WIDTH * HEIGHT * 12) as u64;
+
+    // --- Uncompressed baseline ---
+    {
+        let mut group = c.benchmark_group("synth-uncompressed");
+        group.sample_size(10);
+
+        let t = encode::<RGB8>(
+            &rgb8,
+            WIDTH,
+            HEIGHT,
+            Compression::Uncompressed,
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGBA8>(
+            &rgba8,
+            WIDTH,
+            HEIGHT,
+            Compression::Uncompressed,
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgba8))
+            .bench_function("rgba8", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<Gray8>(
+            &gray8,
+            WIDTH,
+            HEIGHT,
+            Compression::Uncompressed,
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_gray8))
+            .bench_function("gray8", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB16>(
+            &rgb16,
+            WIDTH,
+            HEIGHT,
+            Compression::Uncompressed,
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb16))
+            .bench_function("rgb16", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<Gray16>(
+            &gray16,
+            WIDTH,
+            HEIGHT,
+            Compression::Uncompressed,
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_gray16))
+            .bench_function("gray16", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        group.finish();
+    }
+
+    // --- Predictor overhead isolation (deflate-1, with vs without predictor) ---
+    {
+        let mut group = c.benchmark_group("synth-predictor");
+        group.sample_size(10);
+
+        let t = encode::<RGB8>(
+            &rgb8,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8-deflate-none", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB8>(
+            &rgb8,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::Horizontal,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8-deflate-hpred", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB16>(
+            &rgb16,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb16))
+            .bench_function("rgb16-deflate-none", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB16>(
+            &rgb16,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::Horizontal,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb16))
+            .bench_function("rgb16-deflate-hpred", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB32Float>(
+            &rgb_f32,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::None,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_f32x3))
+            .bench_function("rgb-f32-deflate-none", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB32Float>(
+            &rgb_f32,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::FloatingPoint,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_f32x3))
+            .bench_function("rgb-f32-deflate-fpred", |b| {
+                b.iter(|| decode_tiff_bytes(&t))
+            });
+
+        group.finish();
+    }
+
+    // --- LZW vs Deflate comparison ---
+    {
+        let mut group = c.benchmark_group("synth-compression");
+        group.sample_size(10);
+
+        let t = encode::<RGB8>(
+            &rgb8,
+            WIDTH,
+            HEIGHT,
+            Compression::Deflate(1),
+            Predictor::Horizontal,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8-deflate-hpred", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB8>(
+            &rgb8,
+            WIDTH,
+            HEIGHT,
+            Compression::Lzw,
+            Predictor::Horizontal,
+        );
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8-lzw-hpred", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB8>(&rgb8, WIDTH, HEIGHT, Compression::Lzw, Predictor::None);
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8-lzw-none", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        let t = encode::<RGB8>(&rgb8, WIDTH, HEIGHT, Compression::Packbits, Predictor::None);
+        group
+            .throughput(Throughput::Bytes(raw_rgb8))
+            .bench_function("rgb8-packbits", |b| b.iter(|| decode_tiff_bytes(&t)));
+
+        group.finish();
+    }
+}

benches/lzw.rs

@@ -9,9 +9,9 @@ use tiff::decoder::Decoder;
 fn read_image(image: &[u8]) {
     let image = std::io::Cursor::new(image);
     let decoder = Decoder::open(black_box(image));
-
     let mut reader = decoder.unwrap();
     while reader.more_images() {
+        reader.next_directory().unwrap();
         reader.read_image().unwrap();
     }
 }

examples/decode.rs

@@ -2,28 +2,30 @@ use tiff::decoder::{BufferLayoutPreference, Decoder, DecodingSampleBuffer, Decod
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let Some(image) = std::env::args_os().nth(1) else {
-        eprintln!("Usage: decode FILE");
+        eprintln!("Usage: decode FILE [--lenient]");
         return Ok(());
     };
 
+    let lenient = std::env::args().nth(2).as_deref() == Some("--lenient");
+
     let file = std::fs::File::open(image)?;
     let io = std::io::BufReader::new(file);
-    let mut reader = Decoder::open(io)?;
+    let mut reader = Decoder::open(io)?.with_lenient(lenient);
 
     let mut data = DecodingSampleBuffer::I8(vec![]);
 
     for i in 0u32.. {
+        if !reader.more_images() {
+            break;
+        }
+
+        reader.next_directory()?;
+
         let colortype = reader.colortype()?;
         let dimensions = reader.dimensions()?;
         let layout = reader.read_image_to_buffer(&mut data)?;
 
         debug_planes(i, &mut data, &layout, &colortype, dimensions);
-
-        if !reader.more_images() {
-            break;
-        }
-
-        reader.next_image()?
     }
 
     Ok(())

examples/profile_decode.rs

@@ -0,0 +1,130 @@
+//! Profiling helper: encodes and decodes several TIFF configurations.
+//! Run under callgrind: `valgrind --tool=callgrind target/release/examples/profile_decode`
+use std::io::Cursor;
+use tiff::decoder::Decoder;
+use tiff::encoder::colortype::{Gray8, RGB32Float, RGB16, RGB8};
+use tiff::encoder::{Compression, Predictor, TiffEncoder};
+
+const WIDTH: u32 = 2048;
+const HEIGHT: u32 = 2048;
+const ITERS: usize = 3;
+
+fn generate_rgb8(w: u32, h: u32) -> Vec<u8> {
+    (0..w * h * 3).map(|i| (i % 256) as u8).collect()
+}
+
+fn generate_rgb16(w: u32, h: u32) -> Vec<u16> {
+    (0..w * h * 3).map(|i| (i % 65536) as u16).collect()
+}
+
+fn generate_rgb_f32(w: u32, h: u32) -> Vec<f32> {
+    (0..w * h * 3)
+        .map(|i| (i as f32) / (w * h * 3) as f32)
+        .collect()
+}
+
+fn generate_gray8(w: u32, h: u32) -> Vec<u8> {
+    (0..w * h).map(|i| (i % 256) as u8).collect()
+}
+
+fn encode<C: tiff::encoder::colortype::ColorType>(
+    data: &[C::Inner],
+    w: u32,
+    h: u32,
+    compression: Compression,
+    predictor: Predictor,
+) -> Vec<u8>
+where
+    [C::Inner]: tiff::encoder::TiffValue,
+{
+    let mut buf = Cursor::new(Vec::new());
+    TiffEncoder::new(&mut buf)
+        .unwrap()
+        .with_predictor(predictor)
+        .with_compression(compression)
+        .write_image::<C>(w, h, data)
+        .unwrap();
+    buf.into_inner()
+}
+
+fn decode(data: &[u8]) {
+    let cursor = Cursor::new(data);
+    let mut decoder = Decoder::open(cursor).unwrap();
+    decoder.next_image().unwrap();
+    let _ = decoder.read_image().unwrap();
+}
+
+fn main() {
+    let rgb8 = generate_rgb8(WIDTH, HEIGHT);
+    let rgb16 = generate_rgb16(WIDTH, HEIGHT);
+    let rgb_f32 = generate_rgb_f32(WIDTH, HEIGHT);
+    let gray8 = generate_gray8(WIDTH, HEIGHT);
+
+    let cases: Vec<(&str, Vec<u8>)> = vec![
+        (
+            "deflate-rgb8-hpredict",
+            encode::<RGB8>(
+                &rgb8,
+                WIDTH,
+                HEIGHT,
+                Compression::Deflate(1),
+                Predictor::Horizontal,
+            ),
+        ),
+        (
+            "deflate-gray8-hpredict",
+            encode::<Gray8>(
+                &gray8,
+                WIDTH,
+                HEIGHT,
+                Compression::Deflate(1),
+                Predictor::Horizontal,
+            ),
+        ),
+        (
+            "deflate-rgb16-hpredict",
+            encode::<RGB16>(
+                &rgb16,
+                WIDTH,
+                HEIGHT,
+                Compression::Deflate(1),
+                Predictor::Horizontal,
+            ),
+        ),
+        (
+            "deflate-rgb-f32-fpredict",
+            encode::<RGB32Float>(
+                &rgb_f32,
+                WIDTH,
+                HEIGHT,
+                Compression::Deflate(1),
+                Predictor::FloatingPoint,
+            ),
+        ),
+        (
+            "lzw-rgb8-no-pred",
+            encode::<RGB8>(&rgb8, WIDTH, HEIGHT, Compression::Lzw, Predictor::None),
+        ),
+        (
+            "lzw-rgb8-hpredict",
+            encode::<RGB8>(
+                &rgb8,
+                WIDTH,
+                HEIGHT,
+                Compression::Lzw,
+                Predictor::Horizontal,
+            ),
+        ),
+    ];
+
+    for (name, tiff_data) in &cases {
+        eprintln!(
+            "=== Profiling: {} ({} bytes encoded) ===",
+            name,
+            tiff_data.len()
+        );
+        for _ in 0..ITERS {
+            decode(tiff_data);
+        }
+    }
+}

fuzz/Cargo.toml

@@ -19,7 +19,7 @@ path = ".."
 members = ["."]
 
 [[bin]]
-name = "decode_image"
+name = "decode_comprehensive"
-path = "fuzz_targets/decode_image.rs"
+path = "fuzz_targets/decode_comprehensive.rs"
 test = false
 doc = false

fuzz/fuzz_targets/decode_comprehensive.rs

@@ -0,0 +1,96 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+use std::io::{Cursor, Read, Seek};
+use tiff::decoder::{Decoder, Limits};
+use tiff::tags::Tag;
+
+fuzz_target!(|data: &[u8]| {
+    // Standalone header parse (separate code path from Decoder::open)
+    let _ = tiff::decoder::TiffHeader::parse(Cursor::new(data));
+
+    let mut decoder = match Decoder::open(Cursor::new(data)) {
+        Ok(d) => d,
+        Err(_) => return,
+    };
+
+    let mut limits = Limits::default();
+    limits.decoding_buffer_size = 512 * 1024;
+    limits.ifd_value_size = 64 * 1024;
+    limits.intermediate_buffer_size = 512 * 1024;
+    decoder = decoder.with_limits(limits);
+
+    // Probe first IFD (opened but image not yet parsed)
+    probe_directory(&mut decoder);
+
+    // Linear IFD iteration via next_directory — tolerates invalid
+    // intermediate IFDs that aren't decodable as images
+    let mut ifd_count = 1u32;
+    while decoder.more_images() && ifd_count < 8 {
+        if decoder.next_directory().is_err() {
+            break;
+        }
+        probe_directory(&mut decoder);
+        ifd_count += 1;
+    }
+
+    // Random-access traversal via seek (different code path: find_nth_ifd
+    // re-walks the IFD chain from the start each time)
+    for i in 0..ifd_count.min(4) as usize {
+        if decoder.seek_to_directory(i).is_ok() {
+            probe_directory(&mut decoder);
+        }
+        // seek_to_image eagerly parses the directory as an Image
+        let _ = decoder.seek_to_image(i);
+    }
+});
+
+fn probe_directory<R: Read + Seek>(decoder: &mut Decoder<R>) {
+    // Tag iteration — exercises value parsing for every tag in the IFD
+    for result in decoder.current_ifd().tag_iter() {
+        let _ = result;
+    }
+
+    // SubIFD / EXIF / GPS directory traversal — exercises read_directory
+    // with potentially adversarial offsets
+    if let Ok(Some(val)) = decoder.current_ifd().find_tag(Tag::SubIfd) {
+        if let Ok(ptrs) = val.into_ifd_vec() {
+            for ptr in ptrs.into_iter().take(4) {
+                let _ = decoder.read_directory(ptr);
+            }
+        }
+    }
+    for tag in [Tag::ExifDirectory, Tag::GpsDirectory] {
+        if let Ok(Some(val)) = decoder.current_ifd().find_tag(tag) {
+            if let Ok(ptr) = val.into_ifd_pointer() {
+                let _ = decoder.read_directory(ptr);
+            }
+        }
+    }
+
+    // Image-level probing — dimensions() triggers ensure_image,
+    // which lazily parses the directory as an Image
+    if decoder.dimensions().is_ok() {
+        let _ = decoder.colortype();
+        let _ = decoder.color_map();
+        let _ = decoder.get_chunk_type();
+        let _ = decoder.chunk_dimensions();
+        let _ = decoder.strip_count();
+        let _ = decoder.tile_count();
+        let _ = decoder.image_buffer_layout();
+        let _ = decoder.image_chunk_buffer_layout(0);
+
+        // Chunk reads at boundaries — first and last exercise
+        // different offset calculations
+        let _ = decoder.read_chunk(0);
+        let chunk_count = decoder
+            .strip_count()
+            .or_else(|_| decoder.tile_count())
+            .unwrap_or(0);
+        if chunk_count > 1 {
+            let _ = decoder.read_chunk(chunk_count - 1);
+        }
+
+        // Full image decode
+        let _ = decoder.read_image();
+    }
+}

fuzz/fuzz_targets/decode_image.rs

@@ -1,31 +0,0 @@
-#![no_main]
-use libfuzzer_sys::fuzz_target;
-
-fuzz_target!(|data: &[u8]| {
-    let mut decoder = if let Ok(d) = tiff::decoder::Decoder::new(std::io::Cursor::new(data)) {
-        d
-    } else {
-        return;
-    };
-
-    let mut limits = tiff::decoder::Limits::default();
-    limits.decoding_buffer_size = 1_000_000;
-    limits.ifd_value_size = 1_000_000;
-    limits.intermediate_buffer_size = 1_000_000;
-
-    decoder = decoder.with_limits(limits);
-    
-    loop {
-        if let Err(_) = decoder.read_image() {
-            break;
-        }
-
-        if !decoder.more_images() {
-            break;
-        }
-
-        if let Err(_) = decoder.next_image() {
-            break;
-        }
-    }
-});

fuzz/tiff.dict

@@ -0,0 +1,139 @@
+# === File headers ===
+
+# Classic TIFF (LE, BE)
+"\x49\x49\x2A\x00"
+"\x4D\x4D\x00\x2A"
+# BigTIFF (LE, BE) — version 43, 8-byte offsets, different parsing paths
+"\x49\x49\x2B\x00\x08\x00\x00\x00"
+"\x4D\x4D\x00\x2B\x00\x08\x00\x00"
+
+# === IFD field type codes (2-byte LE) ===
+# Decoder switches on these; wrong types exercise error paths
+
+"\x01\x00"
+"\x02\x00"
+"\x03\x00"
+"\x04\x00"
+"\x05\x00"
+"\x06\x00"
+"\x07\x00"
+"\x08\x00"
+"\x09\x00"
+"\x0A\x00"
+"\x0B\x00"
+"\x0C\x00"
+"\x0D\x00"
+"\x10\x00"
+"\x11\x00"
+"\x12\x00"
+
+# === IFD tag numbers (2-byte LE) ===
+
+# 256=ImageWidth 257=ImageLength 258=BitsPerSample
+"\x00\x01"
+"\x01\x01"
+"\x02\x01"
+# 259=Compression 262=PhotometricInterpretation
+"\x03\x01"
+"\x06\x01"
+# 273=StripOffsets 274=Orientation
+"\x11\x01"
+"\x12\x01"
+# 277=SamplesPerPixel 278=RowsPerStrip 279=StripByteCounts
+"\x15\x01"
+"\x16\x01"
+"\x17\x01"
+# 282=XResolution 283=YResolution 284=PlanarConfiguration
+"\x1A\x01"
+"\x1B\x01"
+"\x1C\x01"
+# 317=Predictor 320=ColorMap
+"\x3D\x01"
+"\x40\x01"
+# 322=TileWidth 323=TileLength 324=TileOffsets 325=TileByteCounts
+"\x42\x01"
+"\x43\x01"
+"\x44\x01"
+"\x45\x01"
+# 330=SubIfd 338=ExtraSamples 339=SampleFormat
+"\x4A\x01"
+"\x52\x01"
+"\x53\x01"
+# 347=JPEGTables 530=ChromaSubsampling
+"\x5B\x01"
+"\x12\x02"
+# 34665=ExifDirectory 34675=IccProfile 34853=GpsDirectory
+"\x69\x87"
+"\x73\x87"
+"\x25\x88"
+
+# === IFD tag numbers (2-byte BE) ===
+
+"\x01\x00"
+"\x01\x01"
+"\x01\x02"
+"\x01\x03"
+"\x01\x06"
+"\x01\x11"
+"\x01\x12"
+"\x01\x15"
+"\x01\x16"
+"\x01\x17"
+"\x01\x1A"
+"\x01\x1B"
+"\x01\x1C"
+"\x01\x3D"
+"\x01\x40"
+"\x01\x42"
+"\x01\x43"
+"\x01\x44"
+"\x01\x45"
+"\x01\x4A"
+"\x01\x52"
+"\x01\x53"
+"\x01\x5B"
+"\x02\x12"
+"\x87\x69"
+"\x87\x73"
+"\x88\x25"
+
+# === Compression codes (4-byte LE inline SHORT values) ===
+# These are the values stored in the IFD entry for tag 259
+
+# 1=None 2=Huffman 3=Fax3 4=Fax4 5=LZW
+"\x01\x00\x00\x00"
+"\x02\x00\x00\x00"
+"\x03\x00\x00\x00"
+"\x04\x00\x00\x00"
+"\x05\x00\x00\x00"
+# 6=OldJPEG 7=ModernJPEG 8=Deflate
+"\x06\x00\x00\x00"
+"\x07\x00\x00\x00"
+"\x08\x00\x00\x00"
+# 0x8005=PackBits 0x80B2=OldDeflate
+"\x05\x80\x00\x00"
+"\xB2\x80\x00\x00"
+
+# === Useful small values (4-byte LE) ===
+# BitsPerSample=16, =32 (8 already covered as Deflate compression above)
+
+"\x10\x00\x00\x00"
+"\x20\x00\x00\x00"
+
+# === Minimal IFD entries (12-byte LE: tag + type SHORT + count 1 + value) ===
+# These let the fuzzer splice complete valid entries into an IFD
+
+# ImageWidth=1
+"\x00\x01\x03\x00\x01\x00\x00\x00\x01\x00\x00\x00"
+# ImageLength=1
+"\x01\x01\x03\x00\x01\x00\x00\x00\x01\x00\x00\x00"
+# BitsPerSample=8
+"\x02\x01\x03\x00\x01\x00\x00\x00\x08\x00\x00\x00"
+# Compression=None
+"\x03\x01\x03\x00\x01\x00\x00\x00\x01\x00\x00\x00"
+# PhotometricInterpretation=BlackIsZero
+"\x06\x01\x03\x00\x01\x00\x00\x00\x01\x00\x00\x00"
+# SamplesPerPixel=1
+"\x15\x01\x03\x00\x01\x00\x00\x00\x01\x00\x00\x00"
+# RowsPerStrip=1
+"\x16\x01\x03\x00\x01\x00\x00\x00\x01\x00\x00\x00"

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

@@ -363,7 +363,7 @@ impl ::std::fmt::Debug for Entry {
     fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
         fmt.write_str(&format!(
             "Entry {{ type_: {:?}, count: {:?}, offset: {:?} }}",
-            self.type_, self.count, &self.offset
+            self.type_, self.count, self.offset
         ))
     }
 }
@@ -393,7 +393,7 @@ impl Entry {
         self.count
     }
 
-    pub(crate) fn offset(&self) -> &[u8] {
+    pub(crate) fn offset_raw(&self) -> &[u8; 8] {
         &self.offset
     }
 
@@ -583,81 +583,93 @@ impl Entry {
 
         match self.type_ {
             Type::BYTE | Type::UNDEFINED => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(bytes.iter().copied().map(Byte))
                 })
             }
             Type::SBYTE => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(bytes.iter().copied().map(|v| SignedByte(v as i8)))
                 })
             }
             Type::SHORT => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(2)
+                            .as_chunks::<2>()
-                            .map(|ch| Short(u16::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| Short(u16::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::SSHORT => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(2)
+                            .as_chunks::<2>()
-                            .map(|ch| SignedShort(i16::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| SignedShort(i16::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::LONG => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(4)
+                            .as_chunks::<4>()
-                            .map(|ch| Unsigned(u32::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| Unsigned(u32::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::SLONG => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(4)
+                            .as_chunks::<4>()
-                            .map(|ch| Signed(i32::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| Signed(i32::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::FLOAT => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(4)
+                            .as_chunks::<4>()
-                            .map(|ch| Float(f32::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| Float(f32::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::DOUBLE => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(8)
+                            .as_chunks::<8>()
-                            .map(|ch| Double(f64::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| Double(f64::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::RATIONAL => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
-                    v.extend(bytes.chunks_exact(8).map(|ch| {
+                    v.extend(bytes.as_chunks::<8>().0.iter().map(|ch| {
                         Rational(
                             u32::from_ne_bytes(ch[..4].try_into().unwrap()),
                             u32::from_ne_bytes(ch[4..].try_into().unwrap()),
@@ -666,9 +678,9 @@ impl Entry {
                 })
             }
             Type::SRATIONAL => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
-                    v.extend(bytes.chunks_exact(8).map(|ch| {
+                    v.extend(bytes.as_chunks::<8>().0.iter().map(|ch| {
                         SRational(
                             i32::from_ne_bytes(ch[..4].try_into().unwrap()),
                             i32::from_ne_bytes(ch[4..].try_into().unwrap()),
@@ -677,50 +689,58 @@ impl Entry {
                 })
             }
             Type::LONG8 => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(8)
+                            .as_chunks::<8>()
-                            .map(|ch| UnsignedBig(u64::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| UnsignedBig(u64::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::SLONG8 => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(8)
+                            .as_chunks::<8>()
-                            .map(|ch| SignedBig(i64::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| SignedBig(i64::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::IFD => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(4)
+                            .as_chunks::<4>()
-                            .map(|ch| Ifd(u32::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| Ifd(u32::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::IFD8 => {
-                v = Self::vec_with_capacity(self.count, limits)?;
+                v = Self::vec_with_capacity(self.count, self.type_, limits)?;
                 self.decode_values(self.count, self.type_, reader, |bytes| {
                     v.extend(
                         bytes
-                            .chunks_exact(8)
+                            .as_chunks::<8>()
-                            .map(|ch| IfdBig(u64::from_ne_bytes(ch.try_into().unwrap()))),
+                            .0
+                            .iter()
+                            .map(|&ch| IfdBig(u64::from_ne_bytes(ch))),
                     )
                 })
             }
             Type::ASCII => {
                 let n = usize::try_from(self.count)?;
 
-                if n > limits.decoding_buffer_size {
+                if n > limits.ifd_value_size {
-                    return Err(dbg!(TiffError::LimitsExceeded));
+                    return Err(TiffError::LimitsExceeded);
                 }
 
                 let mut out = vec![0; n];
@@ -846,10 +866,20 @@ impl Entry {
 
     fn vec_with_capacity(
         value_count: u64,
+        type_: Type,
         limits: &super::Limits,
     ) -> Result<Vec<Value>, TiffError> {
-        let value_count = usize::try_from(value_count)?;
+        // Check raw file bytes against ifd_value_size.
+        if !type_
+            .value_bytes(value_count)
+            .and_then(|b| usize::try_from(b).map_err(|_| TiffError::LimitsExceeded))
+            .is_ok_and(|raw_len| raw_len <= limits.ifd_value_size)
+        {
+            return Err(TiffError::LimitsExceeded);
+        }
 
+        // Check in-memory Value representation against decoding_buffer_size.
+        let value_count = usize::try_from(value_count)?;
         if value_count > limits.decoding_buffer_size / mem::size_of::<Value>() {
             return Err(TiffError::LimitsExceeded);
         }

src/decoder/image.rs

@@ -36,6 +36,9 @@ impl TileAttributes {
     pub fn tiles_down(&self) -> usize {
         self.image_height.div_ceil(self.tile_length)
     }
+    pub fn tiles_per_plane(&self) -> usize {
+        self.tiles_across() * self.tiles_down()
+    }
     fn padding_right(&self) -> usize {
         (self.tile_width - self.image_width % self.tile_width) % self.tile_width
     }
@@ -97,6 +100,7 @@ pub(crate) struct Image {
     /// run on samples directly and thus skip the outer byte order entirely, except potentially
     /// they have interior byte order treatment.
     pub decompression_to_host_endian: bool,
+    pub lenient: bool,
 }
 
 /// Describes how to read a tile-aligned portion of the image.
@@ -155,35 +159,10 @@ 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),
-            fill_order: 1,
-            color_map: None,
-            decompression_to_host_endian: false,
-        }
-    }
-
     pub fn from_reader<R: Read + Seek>(
         decoder: &mut ValueReader<R>,
         ifd: &Directory,
+        lenient: bool,
     ) -> TiffResult<Image> {
         let mut tag_reader = TagReader { decoder, ifd };
 
@@ -200,7 +179,7 @@ impl Image {
             .map(Value::into_u16)
             .transpose()?
             .and_then(PhotometricInterpretation::from_u16)
-            .ok_or(TiffUnsupportedError::UnknownInterpretation)?;
+            .unwrap_or(PhotometricInterpretation::BlackIsZero);
 
         // Try to parse both the compression method and the number, format, and bits of the included samples.
         // If they are not explicitly specified, those tags are reset to their default values and not carried from previous images.
@@ -480,8 +459,9 @@ impl Image {
             match tag_reader.find_tag(Tag::ColorMap)? {
                 Some(v) => {
                     let map = v.into_u16_vec()?;
-                    let expected_len = 3usize
+                    let expected_len = 1usize
-                        .checked_mul(1usize << bits_per_sample)
+                        .checked_shl(bits_per_sample as u32)
+                        .and_then(|n| n.checked_mul(3))
                         .ok_or(TiffError::LimitsExceeded)?;
                     if map.len() != expected_len {
                         return Err(TiffError::FormatError(
@@ -490,11 +470,11 @@ impl Image {
                     }
                     Some(map)
                 }
-                None => {
+                // A missing palette is not an error. The pixel values of an indexed image are just
-                    return Err(TiffError::FormatError(
+                // indices into the palette, and the palette itself is only display information, so
-                        TiffFormatError::RequiredTagNotFound(Tag::ColorMap),
+                // the image still decodes. Callers observe the absence as `None` from
-                    ));
+                // `Decoder::color_map`.
-                }
+                None => None,
             }
         } else {
             None
@@ -525,14 +505,29 @@ impl Image {
                 compression_method,
                 CompressionMethod::SgiLog | CompressionMethod::SgiLog24
             ),
+            lenient,
         })
     }
 
+    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!(
+        let is_alpha_extra_samples = match self.extra_samples.as_slice().first() {
-            self.extra_samples.as_slice(),
+            Some(ExtraSamples::AssociatedAlpha) | Some(ExtraSamples::UnassociatedAlpha) => true,
-            [ExtraSamples::AssociatedAlpha, ..] | [ExtraSamples::UnassociatedAlpha, ..]
+            // In lenient mode, keep unspecified alpha interpretation logic compatible with libtiff
-        );
+            // See Issue #341
+            Some(ExtraSamples::Unspecified) if self.lenient && self.samples > 3 => true,
+            _ => false,
+        };
 
         match self.photometric_interpretation {
             PhotometricInterpretation::RGB => match self.photometric_samples {
@@ -605,20 +600,30 @@ impl Image {
                     ),
                 )),
             },
-            // Unsupported due to inherently heterogeneous sample types. This is represented as:
+            // CIE L*a*b* (TIFF6 Section 23, pp 110-115) encodes a/b as signed integers
-            // ```
+            // (int8 at 8-bit, int16 at 16-bit) with 0 neutral, while ICC L*a*b*
-            // struct TiffLab /* Interpretation 8* {
+            // (photometric=9) uses unsigned samples with the neutral at the middle of
-            //     pub L: u8, // SampleFormat::Uint
+            // the range. `SampleFormat` applies uniformly to all samples, so it can't
-            //     pub a: i8, // SampleFormat::Int
+            // describe the L=unsigned + a/b=signed mix; instead we take a/b as signed
-            //     pub b: i8, // SampleFormat::Int
+            // from the photometric interpretation (requiring `SampleFormat::Uint`, like
-            // }
+            // the ICCLab arm) and re-bias them to the unsigned ICCLab encoding in
-            // ```
+            // post-processing (see `cielab_to_icclab`). libtiff does the same, decoding
-            PhotometricInterpretation::CIELab => Err(TiffError::UnsupportedError(
+            // both depths (`putcontig8bitCIELab8` / `putcontig8bitCIELab16`, selected by
+            // `initCIELabConversion` in tif_getimage.c line 2216
+            // @ 04884181e8903915038be553bfab404302d98ea0).
+            PhotometricInterpretation::CIELab => match self.photometric_samples {
+                3 if matches!(self.bits_per_sample, 8 | 16)
+                    && matches!(self.sample_format, SampleFormat::Uint) =>
+                {
+                    Ok(ColorType::Lab(self.bits_per_sample))
+                }
+                _ => Err(TiffError::UnsupportedError(
                     TiffUnsupportedError::InterpretationWithBits(
                         PhotometricInterpretation::CIELab,
                         vec![self.bits_per_sample; self.samples as usize],
                     ),
                 )),
+            },
             PhotometricInterpretation::CIELogL => match self.samples {
                 1 if matches!(self.bits_per_sample, 32)
                     && matches!(self.sample_format, SampleFormat::IEEEFP) =>
@@ -674,7 +679,11 @@ impl Image {
                 ),
             )),
             PhotometricInterpretation::RGBPalette => Ok(ColorType::Palette(self.bits_per_sample)),
-            PhotometricInterpretation::TransparencyMask => Err(TiffError::UnsupportedError(
+            // TransparencyMask is a single-channel mask, treat as grayscale.
+            PhotometricInterpretation::TransparencyMask => {
+                Ok(ColorType::Gray(self.bits_per_sample))
+            }
+            PhotometricInterpretation::Unknown(_) => Err(TiffError::UnsupportedError(
                 TiffUnsupportedError::InterpretationWithBits(
                     self.photometric_interpretation,
                     vec![self.bits_per_sample; self.samples as usize],
@@ -726,6 +735,8 @@ impl Image {
             )),
             #[cfg(feature = "zstd")]
             CompressionMethod::ZSTD => Box::new(zstd::Decoder::new(reader)?),
+            #[cfg(all(not(feature = "zstd"), feature = "zstd-safe-rust"))]
+            CompressionMethod::ZSTD => Box::new(zrip_decode::streaming::FrameDecoder::new(reader)),
             CompressionMethod::PackBits => Box::new(PackBitsReader::new(reader, compressed_length)),
             #[cfg(feature = "deflate")]
             CompressionMethod::Deflate | CompressionMethod::OldDeflate => {
@@ -1008,7 +1019,15 @@ impl Image {
             }
             ChunkType::Tile => {
                 let tile_attrs = self.tile_attributes.as_ref().unwrap();
-                let (padding_right, padding_down) = tile_attrs.get_padding(chunk_index as usize);
+                // The chunk index counts the tiles of all planes, but the tile grid repeats per
+                // plane, so only the position within the plane decides the padding.
+                let tiles_per_plane = tile_attrs.tiles_per_plane();
+                let tile = if tiles_per_plane == 0 {
+                    0
+                } else {
+                    chunk_index as usize % tiles_per_plane
+                };
+                let (padding_right, padding_down) = tile_attrs.get_padding(tile);
 
                 let tile_width = tile_attrs.tile_width - padding_right;
                 let tile_length = tile_attrs.tile_length - padding_down;
@@ -1024,6 +1043,7 @@ impl Image {
         buf: &mut [u8],
         layout: &ReadoutLayout,
         chunk_index: u32,
+        scratch: &mut Vec<u8>,
     ) -> TiffResult<()> {
         let ValueReader {
             reader,
@@ -1049,6 +1069,7 @@ impl Image {
             | ColorType::YCbCr(n)
             | ColorType::Gray(n)
             | ColorType::Palette(n)
+            | ColorType::Lab(n)
             | ColorType::Multiband {
                 bit_depth: n,
                 num_samples: _,
@@ -1060,6 +1081,7 @@ impl Image {
             | ColorType::YCbCr(n)
             | ColorType::Gray(n)
             | ColorType::Palette(n)
+            | ColorType::Lab(n)
             | ColorType::Multiband {
                 bit_depth: n,
                 num_samples: _,
@@ -1203,14 +1225,26 @@ impl Image {
                 super::fix_endianness_and_predict(
                     out_row,
                     color_type.bit_depth(),
-                    samples,
+                    data_samples,
                     ByteOrder::native(),
                     predictor,
+                    scratch,
                 );
 
-                if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                // An n-bit predictor delta is stored modulo 2^n, but the
-                    super::invert_colors(out_row, color_type, self.sample_format)?;
+                // reconstruction above accumulated it in the promoted u16/u32
-                }
+                // storage width. Reduce back modulo the declared depth so both
+                // the inverted and non-inverted paths see exact, in-range
+                // values (2^n divides the storage modulus, so one mask after
+                // the row is exact).
+                super::mask_samples_to_bit_depth(out_row, tiff_bps, out_bps, self.sample_format);
+
+                super::post_process_row(
+                    out_row,
+                    photometric_interpretation,
+                    color_type,
+                    self.sample_format,
+                )?;
             }
         } else if is_output_chunk_rows && is_all_bits {
             // Here we can read directly into the output buffer itself.
@@ -1224,12 +1258,26 @@ impl Image {
                     samples,
                     decompressed_byte_order,
                     predictor,
+                    scratch,
                 );
             }
 
-            if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+            // No-op in this branch: promoted layouts (declared depth < storage
-                super::invert_colors(tile, color_type, self.sample_format)?;
+            // width) are handled exclusively by the unpacking branch above.
-            }
+            // Called in every integer branch so they cannot diverge.
+            super::mask_samples_to_bit_depth(
+                tile,
+                layout.tiff_bits_per_sample,
+                layout.output_bits_per_sample,
+                self.sample_format,
+            );
+
+            super::post_process_row(
+                tile,
+                photometric_interpretation,
+                color_type,
+                self.sample_format,
+            )?;
         } else if chunk_row_bytes > data_row_bytes && self.predictor == Predictor::FloatingPoint {
             // The floating point predictor shuffles the padding bytes into the encoded output, so
             // this case is handled specially when needed.
@@ -1239,14 +1287,28 @@ impl Image {
 
                 let row = &mut row[..data_row_bytes];
                 match color_type.bit_depth() {
-                    16 => predict_f16(&mut encoded, row, samples),
+                    16 => {
-                    32 => predict_f32(&mut encoded, row, samples),
+                        let (out, _) = row.as_chunks_mut::<2>();
-                    64 => predict_f64(&mut encoded, row, samples),
+                        predict_f16(&mut encoded, out, samples);
+                    }
+                    32 => {
+                        let (out, _) = row.as_chunks_mut::<4>();
+                        predict_f32(&mut encoded, out, samples);
+                    }
+                    64 => {
+                        let (out, _) = row.as_chunks_mut::<8>();
+                        predict_f64(&mut encoded, out, samples);
+                    }
                     _ => unreachable!(),
                 }
-                if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                // No masking here: the floating point predictor requires
-                    super::invert_colors(row, color_type, self.sample_format)?;
+                // IEEEFP samples, which are never depth-promoted.
-                }
+                super::post_process_row(
+                    row,
+                    photometric_interpretation,
+                    color_type,
+                    self.sample_format,
+                )?;
             }
         } else if is_all_bits {
             // We read row-by-row but each row fits in its output buffer.
@@ -1270,11 +1332,25 @@ impl Image {
                     samples,
                     decompressed_byte_order,
                     predictor,
+                    scratch,
                 );
 
-                if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                // No-op in this branch: promoted layouts only occur in the
-                    super::invert_colors(row, color_type, self.sample_format)?;
+                // unpacking branch. Called so the integer branches cannot
-                }
+                // diverge.
+                super::mask_samples_to_bit_depth(
+                    row,
+                    layout.tiff_bits_per_sample,
+                    layout.output_bits_per_sample,
+                    self.sample_format,
+                );
+
+                super::post_process_row(
+                    row,
+                    photometric_interpretation,
+                    color_type,
+                    self.sample_format,
+                )?;
             }
         } else {
             // The encoded data potentially takes up more space than the output data so we must be
@@ -1301,6 +1377,10 @@ impl Image {
             let photo_range = photometric_bit_end / 8..bits_per_pixel / 8;
             let mut encoded = vec![0u8; chunk_row_bytes];
             for row in buf.chunks_mut(layout.row_stride).take(data_dims.1 as usize) {
+                // Clip to the chunk's data width: border chunks are stored at the full chunk
+                // width, and writing their horizontal padding would spill into the following
+                // output row (and predict/invert would run past the chunk's own columns).
+                let row = &mut row[..data_row_bytes];
                 reader.read_exact(&mut encoded)?;
 
                 Self::compact_photometric_bytes(&mut encoded, row, &photo_range);
@@ -1311,11 +1391,25 @@ impl Image {
                     samples,
                     decompressed_byte_order,
                     predictor,
+                    scratch,
                 );
 
-                if photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                // No-op in this branch: promoted layouts only occur in the
-                    super::invert_colors(row, color_type, self.sample_format)?;
+                // unpacking branch. Called so the integer branches cannot
-                }
+                // diverge.
+                super::mask_samples_to_bit_depth(
+                    row,
+                    layout.tiff_bits_per_sample,
+                    layout.output_bits_per_sample,
+                    self.sample_format,
+                );
+
+                super::post_process_row(
+                    row,
+                    photometric_interpretation,
+                    color_type,
+                    self.sample_format,
+                )?;
             }
         }
 

src/decoder/logluv.rs

@@ -87,15 +87,12 @@ fn packbits_decode<R: Read, const N: usize>(
     reader: &mut R,
     buf: &mut [[u8; N]],
 ) -> std::io::Result<()> {
+    let expected = buf.len();
     for offset in (0..N).rev() {
         let mut i = 0;
         let mut code = [0u8; 1];
 
-        loop {
+        while let Some(pixels) = buf.get_mut(i..) {
-            let Some(pixels) = buf.get_mut(i..) else {
-                break;
-            };
-
             if pixels.is_empty() {
                 break;
             }
@@ -124,6 +121,13 @@ fn packbits_decode<R: Read, const N: usize>(
                 i += usize::from(repeat);
             }
         }
+
+        if i < expected {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::UnexpectedEof,
+                "PackBits RLE decoded fewer pixels than expected",
+            ));
+        }
     }
 
     Ok(())

src/decoder/stream.rs

@@ -141,14 +141,32 @@ pub struct LZWReader<R: Read> {
 impl<R: Read> LZWReader<R> {
     /// Wraps a reader
     pub fn new(reader: R, compressed_length: usize) -> LZWReader<R> {
-        let configuration =
+        let mut buffered = BufReader::with_capacity(
-            weezl::decode::Configuration::with_tiff_size_switch(weezl::BitOrder::Msb, 8)
-                .with_yield_on_full_buffer(true);
-        Self {
-            reader: BufReader::with_capacity(
             (32 * 1024).min(compressed_length),
             reader.take(u64::try_from(compressed_length).unwrap()),
-            ),
+        );
+
+        // `Compression = 5` covers both the current LZW variant and the pre-TIFF-6.0
+        // "old-style" one, with no tag to distinguish them. New-style is MSB-first with
+        // the "early change" code-size switch, and its stream begins with the Clear code
+        // (256) -> first byte 0x80. Old-style is LSB-first *without* the early change
+        // (GIF-style increment timing), and begins with 0x00 followed by a byte with bit
+        // 0 set. This is the heuristic libtiff uses to select its compatibility decoder;
+        // on a short/failed peek we default to the modern variant.
+        let old_style = matches!(
+            buffered.fill_buf(),
+            Ok(head) if head.len() >= 2 && head[0] == 0x00 && head[1] & 0x01 != 0
+        );
+
+        let configuration = if old_style {
+            weezl::decode::Configuration::new(weezl::BitOrder::Lsb, 8)
+        } else {
+            weezl::decode::Configuration::with_tiff_size_switch(weezl::BitOrder::Msb, 8)
+        }
+        .with_yield_on_full_buffer(true);
+
+        Self {
+            reader: buffered,
             decoder: configuration.build(),
         }
     }
@@ -448,7 +466,7 @@ impl Group3Reader {
     ) -> Option<u16> {
         let mut sum = 0u16;
         while let Some(n) = decoder(reader) {
-            sum += n;
+            sum = sum.checked_add(n)?;
             if n < 64 {
                 return Some(sum);
             }
@@ -475,7 +493,10 @@ impl Read for Group3Reader {
                 };
                 match run {
                     Some(len) => {
-                        a0 += len;
+                        a0 = match a0.checked_add(len) {
+                            Some(v) => v,
+                            None => break, // overflow = corrupt data
+                        };
                         transitions.push(a0);
                         is_white = !is_white;
                     }

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
@@ -170,7 +171,7 @@ mod tests {
             dir.get(Tag::Unknown(1))
                 .expect("tag 1 should be present after this chain")
                 .count(),
-            u16::MAX.into()
+            u64::from(u16::MAX)
         );
     }
 

src/encoder/mod.rs

@@ -488,7 +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)

src/tags.rs

@@ -295,7 +295,10 @@ pub enum CompressionMethod(u16) unknown(
 }
 
 tags! {
-pub enum PhotometricInterpretation(u16) {
+pub enum PhotometricInterpretation(u16) unknown(
+    /// A private or extension tag
+    unknown
+) {
     WhiteIsZero = 0,
     BlackIsZero = 1,
     RGB = 2,
@@ -567,6 +570,13 @@ 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 {
@@ -607,26 +617,22 @@ impl ByteOrder {
             return;
         }
 
-        // FIXME: at MSRV 1.89 or higher use `slice::as_chunks_mut`.
         match cls {
             EndianBytes::One => {
                 // No change needed
             }
             EndianBytes::Two => {
-                for chunk in buffer.chunks_exact_mut(2) {
+                for chunk in buffer.as_chunks_mut::<2>().0 {
-                    let chunk: &mut [u8; 2] = chunk.try_into().unwrap();
                     *chunk = u16::from_be_bytes(*chunk).to_le_bytes();
                 }
             }
             EndianBytes::Four => {
-                for chunk in buffer.chunks_exact_mut(4) {
+                for chunk in buffer.as_chunks_mut::<4>().0 {
-                    let chunk: &mut [u8; 4] = chunk.try_into().unwrap();
                     *chunk = u32::from_be_bytes(*chunk).to_le_bytes();
                 }
             }
             EndianBytes::Eight => {
-                for chunk in buffer.chunks_exact_mut(8) {
+                for chunk in buffer.as_chunks_mut::<8>().0 {
-                    let chunk: &mut [u8; 8] = chunk.try_into().unwrap();
                     *chunk = u64::from_be_bytes(*chunk).to_le_bytes();
                 }
             }

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
+            ifd.get_tag_u64(Tag::StripOffsets)
-                .get_tag_u64(Tag::StripOffsets)
                 .expect("Cannot get StripOffsets"),
             16
         );
         assert_eq!(
-            decoder
+            ifd.get_tag_u64(Tag::RowsPerStrip)
-                .get_tag_u64(Tag::RowsPerStrip)
                 .expect("Cannot get RowsPerStrip"),
             64
         );
         assert_eq!(
-            decoder
+            ifd.get_tag_u64(Tag::StripByteCounts)
-                .get_tag_u64(Tag::StripByteCounts)
                 .expect("Cannot get StripByteCounts"),
             12288
         )

tests/decode_geotiff_images.rs

@@ -30,27 +30,25 @@ fn test_geo_tiff() {
                 num_samples: 5
             }
         );
+
+        let mut ifd = decoder.current_ifd();
         assert_eq!(
-            decoder
+            ifd.get_tag_u64(Tag::StripOffsets)
-                .get_tag_u64(Tag::StripOffsets)
                 .expect("Cannot get StripOffsets"),
             418
         );
         assert_eq!(
-            decoder
+            ifd.get_tag_u64(Tag::RowsPerStrip)
-                .get_tag_u64(Tag::RowsPerStrip)
                 .expect("Cannot get RowsPerStrip"),
             10
         );
         assert_eq!(
-            decoder
+            ifd.get_tag_u64(Tag::StripByteCounts)
-                .get_tag_u64(Tag::StripByteCounts)
                 .expect("Cannot get StripByteCounts"),
             1000
         );
         assert_eq!(
-            decoder
+            ifd.get_tag(Tag::ModelPixelScaleTag)
-                .get_tag(Tag::ModelPixelScaleTag)
                 .expect("Cannot get pixel scale")
                 .into_f64_vec()
                 .expect("Cannot get pixel scale"),

tests/decode_images.rs

@@ -1,11 +1,11 @@
 extern crate tiff;
 
 use tiff::decoder::{ifd, Decoder, DecodingSampleBuffer};
-use tiff::tags::{ByteOrder, Type};
+use tiff::tags::{ByteOrder, PhotometricInterpretation, SampleFormat, Type};
 use tiff::ColorType;
 
 use std::fs::File;
-use std::io::{Read, Seek};
+use std::io::{Cursor, Read, Seek};
 use std::path::PathBuf;
 
 const TEST_IMAGE_DIR: &str = "./tests/images/";
@@ -16,7 +16,9 @@ macro_rules! test_image_sum {
         fn $name(file: &str, expected_type: ColorType, expected_sum: $sum_ty) {
             let path = PathBuf::from(TEST_IMAGE_DIR).join(file);
             let img_file = File::open(path).expect("Cannot find test image!");
-            let mut decoder = Decoder::open(img_file).expect("Cannot create decoder");
+            let mut decoder = Decoder::open(img_file)
+                .expect("Cannot create decoder")
+                .with_lenient(true);
 
             decoder.next_image().expect("Cannot read image IFD");
             assert_eq!(decoder.colortype().unwrap(), expected_type);
@@ -404,7 +406,10 @@ 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,
@@ -470,6 +475,78 @@ fn test_tiled_rect_rgb_u8() {
     test_image_sum_u8("tiled-rect-rgb-u8.tif", ColorType::RGB(8), 62081032);
 }
 
+#[test]
+fn test_tiled_extra_samples_border_u8() {
+    // Regression test for https://github.com/image-rs/image-tiff/issues/400
+    //
+    // A tiled image whose dimensions are not multiples of the tile size, with
+    // an extra sample that is discarded on decode. The horizontal padding of
+    // the right border tiles used to be written past the end of the output
+    // row, spilling into the leftmost columns of the following row. The
+    // fixture's tile padding is filled with 0xEE so any spill is visible.
+    let path = PathBuf::from(TEST_IMAGE_DIR).join("tiled-extra-samples-border-u8.tif");
+    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.dimensions().unwrap(), (40, 40));
+    assert_eq!(decoder.colortype().unwrap(), ColorType::RGB(8));
+
+    let DecodingSampleBuffer::U8(data) = decoder.read_image().unwrap() else {
+        panic!("Wrong bit depth")
+    };
+
+    let mut expected = Vec::with_capacity(40 * 40 * 3);
+    for y in 0..40u32 {
+        for x in 0..40u32 {
+            expected.push(((x * 3) % 251) as u8);
+            expected.push(((y * 7) % 251) as u8);
+            expected.push(((x + y) % 251) as u8);
+        }
+    }
+    assert_eq!(data, expected);
+}
+
+#[test]
+fn test_tiled_planar_border_u16() {
+    // A planar (separate) tiled image whose dimensions are not multiples of the tile size.
+    // The tile grid repeats for every plane, but the chunk (tile) index counts all planes, so
+    // the border padding of the second plane used to be looked up with the wrong tile index.
+    // The bottom-right tile of plane 1 then claimed a full tile height, and the decoder ran
+    // past the end of the output buffer.
+    //
+    // Note that `read_image` only decodes the first plane, so this has to go through
+    // `read_image_to_buffer` to reach the tiles that were mis-sized.
+    let path = PathBuf::from(TEST_IMAGE_DIR).join("tiled-planar-2c-16b.tif");
+    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.dimensions().unwrap(), (30, 20));
+    assert_eq!(
+        decoder.colortype().unwrap(),
+        ColorType::Multiband {
+            bit_depth: 16,
+            num_samples: 2
+        }
+    );
+
+    let mut buffer = DecodingSampleBuffer::U16(Vec::new());
+    decoder.read_image_to_buffer(&mut buffer).unwrap();
+    let DecodingSampleBuffer::U16(data) = buffer else {
+        panic!("Wrong bit depth")
+    };
+    assert_eq!(data.len(), 2 * 20 * 30);
+
+    let mut expected = Vec::with_capacity(2 * 20 * 30);
+    for plane in 0..2u16 {
+        for y in 0..20u16 {
+            for x in 0..30u16 {
+                expected.push(1000 * plane + 10 * y + x);
+            }
+        }
+    }
+    assert_eq!(data, expected);
+}
+
 #[test]
 fn test_inner_access() {
     let path = PathBuf::from(TEST_IMAGE_DIR).join("tiled-rect-rgb-u8.tif");
@@ -478,7 +555,8 @@ 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()
@@ -487,13 +565,13 @@ 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()
@@ -821,7 +899,7 @@ fn test_predictor_3_gray_f32() {
 }
 
 #[test]
-#[cfg(feature = "zstd")]
+#[cfg(any(feature = "zstd", feature = "zstd-safe-rust"))]
 fn test_zstd_compression() {
     // gdal_translate -co COMPRESS=ZSTD -co ZSTD_LEVEL=20 int16.tif int16_zstd.tif
     test_image_sum_i16("int16_zstd.tif", ColorType::Gray(16), 354396);
@@ -861,22 +939,22 @@ fn test_image_bytes(
 }
 
 fn byte_order_u16(bytes: &mut [u8]) {
-    for chunk in bytes.chunks_exact_mut(2) {
+    for chunk in bytes.as_chunks_mut::<2>().0 {
-        let n = u16::from_ne_bytes(chunk.try_into().unwrap());
+        let n = u16::from_ne_bytes(*chunk);
         chunk.copy_from_slice(&n.to_le_bytes());
     }
 }
 
 fn byte_order_u32(bytes: &mut [u8]) {
-    for chunk in bytes.chunks_exact_mut(4) {
+    for chunk in bytes.as_chunks_mut::<4>().0 {
-        let n = u32::from_ne_bytes(chunk.try_into().unwrap());
+        let n = u32::from_ne_bytes(*chunk);
         chunk.copy_from_slice(&n.to_le_bytes());
     }
 }
 
 fn byte_order_u64(bytes: &mut [u8]) {
-    for chunk in bytes.chunks_exact_mut(8) {
+    for chunk in bytes.as_chunks_mut::<8>().0 {
-        let n = u64::from_ne_bytes(chunk.try_into().unwrap());
+        let n = u64::from_ne_bytes(*chunk);
         chunk.copy_from_slice(&n.to_le_bytes());
     }
 }
@@ -971,7 +1049,7 @@ fn extra_bits_gray() {
 
 #[test]
 fn extra_bits_rgb() {
-    test_image_sum_u8("extra_bits_rgb_8b.tiff", ColorType::RGB(8), 0);
+    test_image_sum_u8("extra_bits_rgb_8b.tiff", ColorType::RGBA(8), 64);
 }
 
 #[test]
@@ -1053,3 +1131,295 @@ 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);
 }
+
+// ---- Old-style LZW ----
+
+#[test]
+fn test_old_style_lzw() {
+    // Pre-TIFF-6.0 "old-style" LZW: LSB-first bit order with no early-change size
+    // switch. Auto-detected from the stream (first byte 0x00, second byte odd).
+    // Same image as libtiffpic's quad-lzw.tif; the decoded pixels must match.
+    test_image_sum_u8("quad-lzw-compat.tiff", ColorType::RGB(8), 21048924);
+}
+
+// ---- TransparencyMask ----
+
+/// Build a minimal uncompressed 2x2 TIFF in memory, in the requested byte order,
+/// with the given photometric interpretation and the pixel data as a single strip.
+/// `sample_format` is emitted as a SampleFormat tag when `Some`; when `None` the
+/// tag is omitted (the decoder then defaults to unsigned). Pixel bytes must already
+/// be in `byte_order`.
+fn build_raw_tiff(
+    byte_order: ByteOrder,
+    photometric: PhotometricInterpretation,
+    bits_per_sample: u16,
+    samples_per_pixel: u16,
+    sample_format: Option<SampleFormat>,
+    pixel_data: &[u8],
+) -> Vec<u8> {
+    let le = matches!(byte_order, ByteOrder::LittleEndian);
+    let put16 = |buf: &mut Vec<u8>, v: u16| {
+        if le {
+            buf.extend_from_slice(&v.to_le_bytes());
+        } else {
+            buf.extend_from_slice(&v.to_be_bytes());
+        }
+    };
+    let put32 = |buf: &mut Vec<u8>, v: u32| {
+        if le {
+            buf.extend_from_slice(&v.to_le_bytes());
+        } else {
+            buf.extend_from_slice(&v.to_be_bytes());
+        }
+    };
+
+    let width: u16 = 2;
+    let height: u16 = 2;
+    let num_tags: u16 = if sample_format.is_some() { 9 } else { 8 };
+    let ifd_offset: u32 = 8;
+    let ifd_size = 2 + (num_tags as u32) * 12 + 4;
+    let strip_offset = 8 + ifd_size;
+
+    // IFD entries (must be ascending tag order). Tag IDs stay raw for the
+    // ascending-order property; the field type uses the `Type` enum.
+    let mut tags: Vec<(u16, Type, u32)> = vec![
+        (256, Type::SHORT, width as u32),                // ImageWidth
+        (257, Type::SHORT, height as u32),               // ImageLength
+        (258, Type::SHORT, bits_per_sample as u32),      // BitsPerSample
+        (259, Type::SHORT, 1),                           // Compression = None
+        (262, Type::SHORT, photometric.to_u16() as u32), // PhotometricInterpretation
+        (273, Type::LONG, strip_offset),                 // StripOffsets
+        (277, Type::SHORT, samples_per_pixel as u32),    // SamplesPerPixel
+        (279, Type::LONG, pixel_data.len() as u32),      // StripByteCounts
+    ];
+    if let Some(sf) = sample_format {
+        tags.push((339, Type::SHORT, sf.to_u16() as u32)); // SampleFormat (tag 339 > 279)
+    }
+
+    let mut buf = Vec::new();
+    buf.extend_from_slice(if le { b"II" } else { b"MM" });
+    put16(&mut buf, 42);
+    put32(&mut buf, ifd_offset);
+    put16(&mut buf, num_tags);
+
+    for (tag, typ, value) in tags {
+        put16(&mut buf, tag);
+        put16(&mut buf, typ.to_u16());
+        put32(&mut buf, 1); // count
+                            // A SHORT value is left-justified in the 4-byte value field (value in the
+                            // first two bytes, then padding); a LONG fills all four.
+        match typ {
+            Type::SHORT => {
+                put16(&mut buf, value as u16);
+                put16(&mut buf, 0);
+            }
+            _ => put32(&mut buf, value),
+        }
+    }
+
+    put32(&mut buf, 0); // next IFD = 0
+    buf.extend_from_slice(pixel_data);
+    buf
+}
+
+#[test]
+fn test_transparency_mask() {
+    // 2x2 mask: values 0, 255, 128, 64
+    let data = build_raw_tiff(
+        ByteOrder::LittleEndian,
+        PhotometricInterpretation::TransparencyMask,
+        8,
+        1,
+        None,
+        &[0, 255, 128, 64],
+    );
+    let mut decoder = Decoder::open(Cursor::new(&data)).unwrap();
+    decoder.next_image().unwrap();
+
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Gray(8));
+
+    let result = decoder.read_image().unwrap();
+    match result {
+        DecodingSampleBuffer::U8(pixels) => {
+            // TransparencyMask is decoded as grayscale
+            assert_eq!(pixels.len(), 4);
+            assert_eq!(pixels[0], 0);
+            assert_eq!(pixels[1], 255);
+            assert_eq!(pixels[2], 128);
+            assert_eq!(pixels[3], 64);
+        }
+        _ => panic!("Expected U8 buffer"),
+    }
+}
+
+// ---- CIE L*a*b* ----
+
+#[test]
+fn test_cielab_decode() {
+    // 2x2 CIELab image: 3 bytes per pixel (L, a, b)
+    // L=128, a=0 (signed neutral), b=0 (signed neutral)
+    // After re-biasing: a=128 (unsigned neutral), b=128 (unsigned neutral)
+    let pixels: Vec<u8> = vec![
+        128, 0, 0, // pixel 0: L=128, a=0, b=0 (neutral gray)
+        255, 50, 50, // pixel 1: L=255, a=+50, b=+50
+        100, 206, 206, // pixel 2: L=100, a=-50 (as i8), b=-50 (as i8)
+        0, 128, 128, // pixel 3: L=0, a=-128 (as i8), b=-128 (as i8)
+    ];
+
+    let data = build_raw_tiff(
+        ByteOrder::LittleEndian,
+        PhotometricInterpretation::CIELab,
+        8,
+        3,
+        None,
+        &pixels,
+    );
+    let mut decoder = Decoder::open(Cursor::new(&data)).unwrap();
+    decoder.next_image().unwrap();
+
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Lab(8));
+
+    let result = decoder.read_image().unwrap();
+    match result {
+        DecodingSampleBuffer::U8(decoded) => {
+            assert_eq!(decoded.len(), 12); // 4 pixels * 3 channels
+
+            // Pixel 0: L=128, a=0+128=128, b=0+128=128
+            assert_eq!(decoded[0], 128);
+            assert_eq!(decoded[1], 128);
+            assert_eq!(decoded[2], 128);
+
+            // Pixel 1: L=255, a=50+128=178, b=50+128=178
+            assert_eq!(decoded[3], 255);
+            assert_eq!(decoded[4], 178);
+            assert_eq!(decoded[5], 178);
+
+            // Pixel 2: L=100, a=206+128=78 (wrapping), b=206+128=78
+            assert_eq!(decoded[6], 100);
+            assert_eq!(decoded[7], 78);
+            assert_eq!(decoded[8], 78);
+
+            // Pixel 3: L=0, a=128+128=0 (wrapping), b=128+128=0
+            assert_eq!(decoded[9], 0);
+            assert_eq!(decoded[10], 0);
+            assert_eq!(decoded[11], 0);
+        }
+        _ => panic!("Expected U8 buffer"),
+    }
+}
+
+#[test]
+fn test_cielab_decode_16() {
+    // 2x2 16-bit CIELab image: 3 u16 samples per pixel (L, a, b), a/b signed.
+    // Re-biasing maps signed a/b to unsigned by adding 0x8000 (wrapping):
+    //   0 -> 32768, +1000 -> 33768, -1000 -> 31768, -32768 -> 0, +32767 -> 65535.
+    let samples: [u16; 12] = [
+        32768, 0, 0, // pixel 0: L, a=0, b=0 (neutral)
+        65535, 1000, 1000, // pixel 1: a=+1000, b=+1000
+        10000, 64536, 64536, // pixel 2: a=-1000, b=-1000 (as u16)
+        0, 32768, 32767, // pixel 3: a=-32768, b=+32767 (as u16)
+    ];
+    let mut pixels = Vec::new();
+    for s in samples {
+        pixels.extend_from_slice(&s.to_le_bytes());
+    }
+
+    let data = build_raw_tiff(
+        ByteOrder::LittleEndian,
+        PhotometricInterpretation::CIELab,
+        16,
+        3,
+        None,
+        &pixels,
+    );
+    let mut decoder = Decoder::open(Cursor::new(&data)).unwrap();
+    decoder.next_image().unwrap();
+
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Lab(16));
+
+    let result = decoder.read_image().unwrap();
+    match result {
+        DecodingSampleBuffer::U16(decoded) => {
+            assert_eq!(decoded.len(), 12); // 4 pixels * 3 channels
+
+            // L unchanged; a/b re-biased by +0x8000 (wrapping).
+            let expected: [u16; 12] = [
+                32768, 32768, 32768, // pixel 0
+                65535, 33768, 33768, // pixel 1
+                10000, 31768, 31768, // pixel 2
+                0, 0, 65535, // pixel 3
+            ];
+            assert_eq!(decoded, expected);
+        }
+        _ => panic!("Expected U16 buffer"),
+    }
+}
+
+#[test]
+fn test_cielab_decode_16_big_endian() {
+    // Same image and expected output as `test_cielab_decode_16`, but stored as a
+    // big-endian ("MM") TIFF. 16-bit is the case where byte order matters: the
+    // decoder must swap to native before the a/b re-bias, so the result is
+    // identical to the little-endian case.
+    let samples: [u16; 12] = [
+        32768, 0, 0, // pixel 0
+        65535, 1000, 1000, // pixel 1
+        10000, 64536, 64536, // pixel 2
+        0, 32768, 32767, // pixel 3
+    ];
+    let mut pixels = Vec::new();
+    for s in samples {
+        pixels.extend_from_slice(&s.to_be_bytes());
+    }
+
+    let data = build_raw_tiff(
+        ByteOrder::BigEndian,
+        PhotometricInterpretation::CIELab,
+        16,
+        3,
+        None,
+        &pixels,
+    );
+    let mut decoder = Decoder::open(Cursor::new(&data)).unwrap();
+    decoder.next_image().unwrap();
+
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Lab(16));
+
+    let result = decoder.read_image().unwrap();
+    match result {
+        DecodingSampleBuffer::U16(decoded) => {
+            let expected: [u16; 12] = [
+                32768, 32768, 32768, // pixel 0
+                65535, 33768, 33768, // pixel 1
+                10000, 31768, 31768, // pixel 2
+                0, 0, 65535, // pixel 3
+            ];
+            assert_eq!(decoded, expected);
+        }
+        _ => panic!("Expected U16 buffer"),
+    }
+}
+
+#[test]
+fn test_cielab_rejects_non_uint_sample_format() {
+    // CIELab treats a/b as signed via the photometric interpretation and requires
+    // SampleFormat::Uint (matching the ICCLab arm). A file declaring Int must be
+    // rejected rather than silently producing a signed output buffer.
+    let pixels = vec![0u8; 12]; // 2x2, 3 samples, 8-bit
+    let data = build_raw_tiff(
+        ByteOrder::LittleEndian,
+        PhotometricInterpretation::CIELab,
+        8,
+        3,
+        Some(SampleFormat::Int),
+        &pixels,
+    );
+
+    let mut decoder = Decoder::open(Cursor::new(&data)).unwrap();
+    // Rejection may surface at either next_image() or colortype().
+    let rejected = decoder.next_image().is_err() || decoder.colortype().is_err();
+    assert!(
+        rejected,
+        "CIELab with SampleFormat=Int must be rejected, not decoded"
+    );
+}

tests/decode_libtiffpic.rs

@@ -190,7 +190,7 @@ const FILES: &[(&str, Option<u32>)] = &[
     ("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-lzw.tif", Some(0x6055f9ee)), // old-style (LSB) LZW
     ("tests/libtiffpic/quad-tile.tif", Some(0x6055f9ee)),
     ("tests/libtiffpic/README", None),
     ("tests/libtiffpic/smallliz.tif", Some(0)), // unsupported YCbCr chroma subsampling

tests/encode_images.rs

@@ -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<_>>();
@@ -80,7 +81,7 @@ 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())
         );
 
@@ -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<_>>();
@@ -165,7 +167,7 @@ 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::DecodingSampleBuffer::U8(vec![]);
@@ -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()
@@ -776,7 +798,13 @@ 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 {
@@ -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/predict.rs

@@ -233,3 +233,167 @@ fn test_rgb_u64_predict_roundtrip() {
 fn test_ycbcr_u8_predict_roundtrip() {
     test_u8_predict_roundtrip::<colortype::YCbCr8>("tiled-jpeg-ycbcr.tif", ColorType::YCbCr(8));
 }
+
+// ---------------------------------------------------------------------------
+// Extended bit depths (9-15 promoted to u16, 17-31 promoted to u32).
+//
+// A horizontal-predicted n-bit sample stores its delta in exactly n bits,
+// i.e. modulo 2^n, so reconstruction must also be modulo 2^n. The decoder
+// accumulates in the promoted storage width and reduces back to n bits;
+// these tests pin that reduction down with exact pixel values, including
+// deltas that wrap modulo 2^n. The encoder does not support extended
+// depths, so the TIFFs are hand-built.
+// ---------------------------------------------------------------------------
+
+/// Hand-build a minimal little-endian, single-strip, uncompressed grayscale
+/// TIFF with `Predictor::Horizontal` and the given (possibly non-standard)
+/// bit depth. `pixels` are the intended sample values; they are converted to
+/// horizontal differences modulo `2^bits` and bit-packed MSB-first with each
+/// row padded to a byte boundary — the only representation an n-bit field
+/// can hold.
+fn build_gray_hpredict_tiff(
+    width: u32,
+    height: u32,
+    bits: u8,
+    photometric: u16,
+    pixels: &[u32],
+) -> Vec<u8> {
+    let max = ((1u64 << bits) - 1) as u32;
+    let row_samples = width as usize;
+    assert_eq!(pixels.len(), row_samples * height as usize);
+    assert!(pixels.iter().all(|&v| v <= max));
+
+    // Per-row horizontal differencing modulo 2^bits.
+    let mut deltas = Vec::with_capacity(pixels.len());
+    for row in pixels.chunks(row_samples) {
+        for (i, &v) in row.iter().enumerate() {
+            deltas.push(if i == 0 {
+                v
+            } else {
+                v.wrapping_sub(row[i - 1]) & max
+            });
+        }
+    }
+
+    // Bit-pack MSB-first, each row padded to a byte boundary.
+    let row_bytes = (row_samples * bits as usize).div_ceil(8);
+    let mut data = vec![0u8; row_bytes * height as usize];
+    for (r, row) in deltas.chunks(row_samples).enumerate() {
+        for (i, &d) in row.iter().enumerate() {
+            let start = r * row_bytes * 8 + i * bits as usize;
+            for (off, b) in (start..).zip((0..bits).rev()) {
+                if (d >> b) & 1 == 1 {
+                    data[off / 8] |= 0x80 >> (off % 8);
+                }
+            }
+        }
+    }
+
+    // Classic little-endian TIFF: header, strip data, then a single IFD.
+    let mut out = Vec::new();
+    out.extend_from_slice(b"II");
+    out.extend_from_slice(&42u16.to_le_bytes());
+    let data_offset = 8u32;
+    let ifd_offset = data_offset + data.len() as u32;
+    out.extend_from_slice(&ifd_offset.to_le_bytes());
+    out.extend_from_slice(&data);
+
+    const SHORT: u16 = 3;
+    const LONG: u16 = 4;
+    let entries: &[(u16, u16, u32)] = &[
+        (256, LONG, width),                   // ImageWidth
+        (257, LONG, height),                  // ImageLength
+        (258, SHORT, u32::from(bits)),        // BitsPerSample
+        (259, SHORT, 1),                      // Compression: none
+        (262, SHORT, u32::from(photometric)), // PhotometricInterpretation
+        (273, LONG, data_offset),             // StripOffsets
+        (277, SHORT, 1),                      // SamplesPerPixel
+        (278, LONG, height),                  // RowsPerStrip
+        (279, LONG, data.len() as u32),       // StripByteCounts
+        (317, SHORT, 2),                      // Predictor: horizontal
+        (339, SHORT, 1),                      // SampleFormat: unsigned integer
+    ];
+    out.extend_from_slice(&(entries.len() as u16).to_le_bytes());
+    for &(tag, ty, value) in entries {
+        out.extend_from_slice(&tag.to_le_bytes());
+        out.extend_from_slice(&ty.to_le_bytes());
+        out.extend_from_slice(&1u32.to_le_bytes());
+        // A count-1 SHORT payload occupies the low bytes of the value field.
+        out.extend_from_slice(&value.to_le_bytes());
+    }
+    out.extend_from_slice(&0u32.to_le_bytes()); // no next IFD
+    out
+}
+
+fn decode_gray_u16(tiff: Vec<u8>, bits: u8) -> Vec<u16> {
+    let mut decoder = Decoder::open(Cursor::new(tiff)).expect("Cannot create decoder");
+    decoder.next_image().unwrap();
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Gray(bits));
+    match decoder.read_image().unwrap() {
+        DecodingSampleBuffer::U16(res) => res,
+        _ => panic!("Wrong data type"),
+    }
+}
+
+fn decode_gray_u32(tiff: Vec<u8>, bits: u8) -> Vec<u32> {
+    let mut decoder = Decoder::open(Cursor::new(tiff)).expect("Cannot create decoder");
+    decoder.next_image().unwrap();
+    assert_eq!(decoder.colortype().unwrap(), ColorType::Gray(bits));
+    match decoder.read_image().unwrap() {
+        DecodingSampleBuffer::U32(res) => res,
+        _ => panic!("Wrong data type"),
+    }
+}
+
+#[test]
+fn test_gray12_hpredict_wraparound_exact() {
+    // Pixel row [4095, 0, 1] encodes as deltas [4095, 1, 1] (mod 2^12).
+    // u16 accumulation yields [4095, 4096, 4097]; reduction modulo 2^12
+    // must restore [4095, 0, 1]. Saturating instead would corrupt the two
+    // wrapped samples to 4095.
+    let tiff = build_gray_hpredict_tiff(3, 1, 12, 1, &[4095, 0, 1]);
+    assert_eq!(decode_gray_u16(tiff, 12), vec![4095, 0, 1]);
+}
+
+#[test]
+fn test_gray12_hpredict_wraparound_white_is_zero_exact() {
+    // Same stored samples with PhotometricInterpretation = WhiteIsZero:
+    // after the mod-2^12 reduction the decoder inverts as (2^12 - 1) - v.
+    let tiff = build_gray_hpredict_tiff(3, 1, 12, 0, &[4095, 0, 1]);
+    assert_eq!(decode_gray_u16(tiff, 12), vec![0, 4095, 4094]);
+}
+
+#[test]
+fn test_gray20_hpredict_wraparound_exact() {
+    // The same wrap-around shape on the u32 storage path (17-31 bits).
+    let tiff = build_gray_hpredict_tiff(3, 1, 20, 1, &[0xF_FFFF, 0, 1]);
+    assert_eq!(decode_gray_u32(tiff, 20), vec![0xF_FFFF, 0, 1]);
+}
+
+#[test]
+fn test_extended_depth_hpredict_random_roundtrip() {
+    // Deterministic pseudo-random pixels across a spread of extended depths;
+    // encode-then-decode must be the identity for every sample, including
+    // every mod-2^n wrap-around the differencing produces. Three rows verify
+    // that prediction restarts per row.
+    let mut state = 0x243F_6A88_85A3_08D3u64;
+    let mut next = move || {
+        state = state
+            .wrapping_mul(6364136223846793005)
+            .wrapping_add(1442695040888963407);
+        (state >> 33) as u32
+    };
+    for &bits in &[9u8, 11, 12, 15] {
+        let max = (1u32 << bits) - 1;
+        let pixels: Vec<u32> = (0..16 * 3).map(|_| next() & max).collect();
+        let tiff = build_gray_hpredict_tiff(16, 3, bits, 1, &pixels);
+        let expected: Vec<u16> = pixels.iter().map(|&v| v as u16).collect();
+        assert_eq!(decode_gray_u16(tiff, bits), expected, "bits={bits}");
+    }
+    for &bits in &[17u8, 20, 25, 31] {
+        let max = ((1u64 << bits) - 1) as u32;
+        let pixels: Vec<u32> = (0..16 * 3).map(|_| next() & max).collect();
+        let tiff = build_gray_hpredict_tiff(16, 3, bits, 1, &pixels);
+        assert_eq!(decode_gray_u32(tiff, bits), pixels, "bits={bits}");
+    }
+}