Bump version to 0.11

Recognize Ycbcr/Chroma subsampling tags

CHANGES.md

@@ -1,4 +1,4 @@
-# Version 0.10.4 (unreleased)
+# Version 0.11.0
 
 - `Directory` now implements `FromIterator<(Tag, Value)>`.
 
@@ -10,6 +10,45 @@ Changes:
   as unspecified relation.  Previously, these may have been interpreted as
   alpha by the total sample count (e.g. RgbA if 4 samples under a photometric
   interpretation of RGB).
+- The decoder handles planar data, current limited to non-subsampled channels.
+  The `Decoder::read_image` method return planes one-after-another depending on
+  the size of the buffer that was passed.
+- `Decoder::read_image_to_buffer` now takes `&mut DecodingResult` and resizes
+  it according to the required layout. Previously, a borrowed `DecodingBuffer`
+  was passed which can be replaced by calling `as_bytes_mut` and
+  `read_image_bytes`.
+- Several methods of tags are now `const`. Note that does not guarantee any
+  particular value when calling these methods.
+
+Fixes:
+- Fix a bug in the uncompressed encoder that could lead to short writes, i.e.
+  data silently dropped when the underlying writer did not accept all data in a
+  single write call.
+- Encoding YCbCr data now writes the `ChromaSubsampling` tag as `(1, 1)` to
+  indicate no subsampling, instead of leaving it at its default of `(2, 2)`.
+- The decoder will reject subsampled YCbCr data as there is no upsampling
+  routine, except for JPEG compressed images where the JPEG decoders handles
+  this. Since the buffer in that case indicates a full-sized plane for all
+  color samples any future support for the tag will upsample all planes (at
+  least within this major version).
+
+Additions:
+- Added support for the `CieLab` color type.
+- Added `DecodingResult::resize_to` to create a buffer with a matching sample
+  type and dimensions.
+- Added `ByteOrder::native` to access the platform's native endianness.
+- Added `ByteOrder::convert` to change the byte-order of values in a byte
+  buffer, depending on their `Type` as described at runtime.
+- Added `DirectoryOffset::new` to encode a directory whose offset is known to
+  the caller but that has not been written through the encoder itself.
+- Added `Encoder::extra_samples` to encode images with more samples than their
+  color's trait implementation would otherwise suggest.
+- Added `DirectoryEncoder::extend_from` to encode multiple tag entries from a
+  directory whose values were written to the file by means outside the
+  encoder's control.
+- Added `Decoder::read_coding_unit_bytes` to retrieve data of corresponding
+  coordinates from potentially planar data, which is encoded in multiple chunks
+  of the file.
 
 # Version 0.10.3
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tiff"
-version = "0.10.3"
+version = "0.11.0"
 edition = "2021"
 resolver = "2"
 

src/decoder/image.rs

@@ -85,6 +85,7 @@ pub(crate) struct Image {
     pub tile_attributes: Option<TileAttributes>,
     pub chunk_offsets: Vec<u64>,
     pub chunk_bytes: Vec<u64>,
+    pub chroma_subsampling: (u16, u16),
 }
 
 /// Describes how to read a tile-aligned portion of the image.
@@ -95,6 +96,19 @@ pub(crate) struct ReadoutLayout {
     pub planar_config: PlanarConfiguration,
 
     /// The sample interpretation (interpret with planar_config).
+    ///
+    /// FIXME: we should not require this here. The ability to turn out the raw bytes from the
+    /// sample arrays is very different from turning out interpretable color. Firstly we can always
+    /// readout `Multiband` but currently only use that ColorType in special circumstances (it must
+    /// not overlap cases where actually want to use a ColorType).
+    ///
+    /// And then we have CIE Lab, which uses a tuple of `(u8, i8, i8)`, that is still filterable
+    /// but still not represented by any of our `DecoderResult` variants. Other color variants
+    /// depend on extra tags (YCbCrCoefficients/0x0211) and we don't have a good side channel to
+    /// tag the output with all that TIFF specific information, so arguably we should process and
+    /// apply those to the data so it becomes a self-contained representation.
+    ///
+    /// This should be computed at a higher level, in `Decoder`, instead.
     pub color: ColorType,
     /// The number of bytes from one row to another.
     pub minimum_row_stride: usize,
@@ -262,6 +276,25 @@ impl Image {
             .transpose()?
             .unwrap_or(PlanarConfiguration::Chunky);
 
+        let ycbcr_subsampling = tag_reader.find_tag_uint_vec::<u16>(Tag::ChromaSubsampling)?;
+
+        let chroma_subsampling = if let Some(subsamples) = &ycbcr_subsampling {
+            let [a, b] = subsamples.as_slice() else {
+                return Err(TiffError::FormatError(TiffFormatError::InvalidCountForTag(
+                    Tag::ChromaSubsampling,
+                    subsamples.len(),
+                )));
+            };
+
+            // ImageWidth and ImageLength are constrained to be integer multiples of
+            // YCbCrSubsampleHoriz and YCbCrSubsampleVert respectively. TileWidth and TileLength
+            // have the same constraints. RowsPerStrip must be an integer multiple of
+            // YCbCrSubsampleVert.
+            (*a, *b)
+        } else {
+            (2, 2)
+        };
+
         let planes = match planar_config {
             PlanarConfiguration::Chunky => 1,
             PlanarConfiguration::Planar => samples,
@@ -373,6 +406,7 @@ impl Image {
             tile_attributes,
             chunk_offsets,
             chunk_bytes,
+            chroma_subsampling,
         })
     }
 
@@ -435,15 +469,60 @@ impl Image {
                     }),
                 }
             }
-            // TODO: this is bad we should not fail at this point
+            // ```
-            PhotometricInterpretation::RGBPalette
+            // struct IccLab /* Interpretation 9* {
-            | PhotometricInterpretation::TransparencyMask
+            //     pub L: u8, // SampleFormat::Uint
-            | PhotometricInterpretation::CIELab => Err(TiffError::UnsupportedError(
+            //     pub a: u8, // SampleFormat::Uint, defined as TiffLab::a + 128
+            //     pub b: u8, // SampleFormat::Uint, defined as TiffLab::b + 128
+            // }
+            // ```
+            PhotometricInterpretation::IccLab => match self.photometric_samples {
+                3 if matches!(self.sample_format, SampleFormat::Uint) => {
+                    Ok(ColorType::Lab(self.bits_per_sample))
+                }
+                _ => Err(TiffError::UnsupportedError(
+                    TiffUnsupportedError::InterpretationWithBits(
+                        self.photometric_interpretation,
+                        vec![self.bits_per_sample; self.samples as usize],
+                    ),
+                )),
+            },
+            // Unsupported due to inherently heterogeneous sample types. This is represented as:
+            // ```
+            // struct TiffLab /* Interpretation 8* {
+            //     pub L: u8, // SampleFormat::Uint
+            //     pub a: i8, // SampleFormat::Int
+            //     pub b: i8, // SampleFormat::Int
+            // }
+            // ```
+            PhotometricInterpretation::CIELab => Err(TiffError::UnsupportedError(
                 TiffUnsupportedError::InterpretationWithBits(
-                    self.photometric_interpretation,
+                    PhotometricInterpretation::CIELab,
                     vec![self.bits_per_sample; self.samples as usize],
                 ),
             )),
+            // Unsupported due to extra unfiltering and conversion steps. We need to find the
+            // Decode tag (SRATIONAL; 2 * SamplesPerPixel) and apply the following conversion:
+            //
+            // L* = Decode[0] + Lsample x (Decode[1] - Decode[0]) / (2^n -1)
+            // …
+            //
+            // So we'll have a larger depth in the output and either worry about reducing fractions
+            // or turn everything into floats. That's a lot of decisions.
+            PhotometricInterpretation::ItuLab => Err(TiffError::UnsupportedError(
+                TiffUnsupportedError::InterpretationWithBits(
+                    PhotometricInterpretation::CIELab,
+                    vec![self.bits_per_sample; self.samples as usize],
+                ),
+            )),
+            PhotometricInterpretation::RGBPalette | PhotometricInterpretation::TransparencyMask => {
+                Err(TiffError::UnsupportedError(
+                    TiffUnsupportedError::InterpretationWithBits(
+                        self.photometric_interpretation,
+                        vec![self.bits_per_sample; self.samples as usize],
+                    ),
+                ))
+            }
         }
     }
 
@@ -657,6 +736,23 @@ impl Image {
             ));
         }
 
+        // Only this color type interprets the tag, which is defined with a default of (2, 2)
+        if matches!(color, ColorType::YCbCr(_)) && self.chroma_subsampling != (1, 1) {
+            // The JPEG library does upsampling for us and defines its buffers correctly
+            // (presumably). All other compression schemes are not supported..
+            //
+            // NOTE: as explained in <fa225e820b96bef35f01bf4685654beeb4a8df0c> we may be better
+            // off supporting this tag by consistently upsampling, not by adjusting the buffer
+            // size. At least as a default this makes more sense and is much more permissive in
+            // case the compression stream disagrees with the tags (we would not have enough / or
+            // the wrong buffer layout if we only asked for subsampled planes in a planar layout).
+            if !matches!(self.compression_method, CompressionMethod::ModernJPEG) {
+                return Err(TiffError::UnsupportedError(
+                    TiffUnsupportedError::ChromaSubsampling,
+                ));
+            }
+        }
+
         Ok(ReadoutLayout {
             planar_config: self.planar_config,
             color,

src/decoder/mod.rs

@@ -860,6 +860,7 @@ impl<R: Read + Seek> Decoder<R> {
                 tile_attributes: None,
                 chunk_offsets: Vec::new(),
                 chunk_bytes: Vec::new(),
+                chroma_subsampling: (2, 2),
             },
         };
         decoder.next_image()?;
@@ -1277,7 +1278,7 @@ impl<R: Read + Seek> Decoder<R> {
     ///
     /// It will re-allocate the buffer into the correct type and size, within the decoder's
     /// configured limits, and then pass it to the underlying method. This is essentially a
-    /// type-safe wrapper around the raw [`Self::read_chunk_to_bytes`] method.
+    /// type-safe wrapper around the raw [`Self::read_chunk_bytes`] method.
     ///
     /// Note that for planar images each chunk contains only one sample of the underlying data.
     pub fn read_chunk_to_buffer(

src/encoder/mod.rs

@@ -11,7 +11,10 @@ use std::{
 use crate::{
     decoder::ifd::Entry,
     error::{TiffResult, UsageError},
-    tags::{CompressionMethod, ExtraSamples, IfdPointer, ResolutionUnit, SampleFormat, Tag, Type},
+    tags::{
+        CompressionMethod, ExtraSamples, IfdPointer, PhotometricInterpretation, ResolutionUnit,
+        SampleFormat, Tag, Type,
+    },
     Directory, TiffError, TiffFormatError,
 };
 
@@ -565,6 +568,12 @@ impl<'a, W: 'a + Write + Seek, T: ColorType, K: TiffKind> ImageEncoder<'a, W, T,
 
         encoder.write_tag(Tag::PhotometricInterpretation, <T>::TIFF_VALUE.to_u16())?;
 
+        if matches!(<T>::TIFF_VALUE, PhotometricInterpretation::YCbCr) {
+            // The default for this tag is 2,2 for subsampling but we do not support such a
+            // transformation. Instead all samples must be provided.
+            encoder.write_tag(Tag::ChromaSubsampling, &[1u16, 1u16][..])?;
+        }
+
         encoder.write_tag(Tag::RowsPerStrip, u32::try_from(rows_per_strip)?)?;
 
         encoder.write_tag(

src/error.rs

@@ -90,6 +90,9 @@ quick_error! {
         InvalidTypeForTag {
             display("tag has invalid type")
         }
+        InvalidCountForTag(tag: Tag, len: usize) {
+            display("tag `{tag:?}` with incorrect number of elements ({len}) encountered")
+        }
         StripTileTagConflict {
             display("file should contain either (StripByteCounts and StripOffsets) or (TileByteCounts and TileOffsets), other combination was found")
         }
@@ -156,6 +159,9 @@ quick_error! {
         UnsupportedInterpretation(interpretation: PhotometricInterpretation) {
             display("unsupported photometric interpretation \"{interpretation:?}\"")
         }
+        ChromaSubsampling {
+            display("chroma subsampling of YCbCr color is unsupported")
+        }
         MisalignedTileBoundaries {
             display("tile rows are not aligned to byte boundaries")
         }

src/lib.rs

@@ -44,6 +44,9 @@ pub enum ColorType {
     /// Pixel is YCbCr
     YCbCr(u8),
 
+    /// Pixel is CIE L*a*b* (ICC LAb)
+    Lab(u8),
+
     /// Pixel has multiple bands/channels
     Multiband { bit_depth: u8, num_samples: u16 },
 }
@@ -58,6 +61,7 @@ impl ColorType {
             | ColorType::CMYK(b)
             | ColorType::CMYKA(b)
             | ColorType::YCbCr(b)
+            | ColorType::Lab(b)
             | ColorType::Multiband { bit_depth: b, .. } => b,
         }
     }
@@ -72,6 +76,7 @@ impl ColorType {
             ColorType::CMYK(_) => 4,
             ColorType::CMYKA(_) => 5,
             ColorType::YCbCr(_) => 3,
+            ColorType::Lab(_) => 3,
             ColorType::Multiband { num_samples, .. } => num_samples,
         }
     }

src/tags.rs

@@ -20,7 +20,7 @@ macro_rules! tags {
 
         impl $name {
             #[inline(always)]
-            fn __from_inner_type(n: $ty) -> Result<Self, $ty> {
+            const fn __from_inner_type(n: $ty) -> Result<Self, $ty> {
                 match n {
                     $( $val => Ok($name::$tag), )*
                     n => Err(n),
@@ -28,7 +28,7 @@ macro_rules! tags {
             }
 
             #[inline(always)]
-            fn __to_inner_type(&self) -> $ty {
+            const fn __to_inner_type(&self) -> $ty {
                 match *self {
                     $( $name::$tag => $val, )*
                     $( $name::Unknown($unknown_doc) => { $unknown_doc }, )*
@@ -42,19 +42,25 @@ macro_rules! tags {
     ($name:tt, u16, $($unknown_doc:ident)*) => {
         impl $name {
             #[inline(always)]
-            pub fn from_u16(val: u16) -> Option<Self> {
+            pub const fn from_u16(val: u16) -> Option<Self> {
-                Self::__from_inner_type(val).ok()
+                match Self::__from_inner_type(val) {
+                    Ok(v) => Some(v),
+                    Err(_) => None,
+                }
             }
 
             $(
             #[inline(always)]
-            pub fn from_u16_exhaustive($unknown_doc: u16) -> Self {
+            pub const fn from_u16_exhaustive($unknown_doc: u16) -> Self {
-                Self::__from_inner_type($unknown_doc).unwrap_or_else(|_| $name::Unknown($unknown_doc))
+                match Self::__from_inner_type($unknown_doc) {
+                    Ok(v) => v,
+                    Err(_) => $name::Unknown($unknown_doc),
+                }
             }
             )*
 
             #[inline(always)]
-            pub fn to_u16(&self) -> u16 {
+            pub const fn to_u16(&self) -> u16 {
                 Self::__to_inner_type(self)
             }
         }
@@ -122,6 +128,11 @@ pub enum Tag(u16) unknown(
     SMaxSampleValue = 341, // TODO add support
     // JPEG
     JPEGTables = 347,
+    // Subsampling
+    #[doc(alias = "YCbCrSubsampling")]
+    ChromaSubsampling = 530, // TODO add support
+    #[doc(alias = "YCbCrPositioning")]
+    ChromaPositioning = 531, // TODO add support
     // GeoTIFF
     ModelPixelScaleTag = 33550, // (SoftDesk)
     ModelTransformationTag = 34264, // (JPL Carto Group)
@@ -266,6 +277,8 @@ pub enum PhotometricInterpretation(u16) {
     CMYK = 5,
     YCbCr = 6,
     CIELab = 8,
+    IccLab = 9,
+    ItuLab = 10,
 }
 }