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Revert "feat: add YCbCr chroma subsampling support for non-JPEG compression"

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This reverts commit 83409cbdf3.
This commit is contained in:
Lilith River committed 2026-03-11 00:39:37 -06:00
1 parent 617dc6eed8
commit 85215e81e3
3 files changed
+14 -107
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src/decoder/image.rs
+10 -19
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@@ -952,10 +952,15 @@ 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. For other compression methods,
// the expand_chunk pipeline wraps the decompressor in a YCbCrUpsamplingReader
// that converts the subsampled block layout to full-resolution pixel rows.
if matches!(self.planar_config, PlanarConfiguration::Planar) {
// 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,
));
@@ -1155,7 +1160,7 @@ impl Image {
let is_all_bits = samples == data_samples;
let is_output_chunk_rows = layout.row_stride == chunk_row_bytes;
let mut reader: Box<dyn Read> = Self::create_reader(
let mut reader = Self::create_reader(
reader.inner(),
compression_method,
*compressed_bytes,
@@ -1165,20 +1170,6 @@ impl Image {
self.fill_order,
)?;
// For non-JPEG YCbCr with chroma subsampling, wrap the decompressor in an
// upsampling reader that converts the subsampled block layout to full-resolution
// pixel rows. JPEG handles upsampling internally.
if matches!(color_type, ColorType::YCbCr(_))
&& self.chroma_subsampling != (1, 1)
&& !matches!(compression_method, CompressionMethod::ModernJPEG)
{
reader = Box::new(super::stream::YCbCrUpsamplingReader::new(
reader,
data_dims,
self.chroma_subsampling,
));
}
// Extended bit depths (9-15, 17-31): packed N-bit samples must be unpacked to
// standard-width output samples before endianness fix and predictor.
let needs_unpacking = layout.tiff_bits_per_sample != layout.output_bits_per_sample