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Tiff: Support decoding f16 images #3015

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c4c4a13
Add support for decoding fp16 TIFF images
RunDevelopment Jun 8, 2026
ad1e61c
Merge branch 'main' into tiff-f16
RunDevelopment Jun 8, 2026
bc1a5b0
Merge branch 'main' into tiff-f16
RunDevelopment Jul 16, 2026
51b43c8
Fix color type typo
RunDevelopment Jul 16, 2026
c802566
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RunDevelopment Jul 16, 2026
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18 changes: 18 additions & 0 deletions src/codecs/tiff.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,7 @@ where
(tiff::ColorType::Gray(1), Uint) => ColorType::L8,
(tiff::ColorType::Gray(8), Uint) => ColorType::L8,
(tiff::ColorType::Gray(16), Uint) => ColorType::L16,
(tiff::ColorType::Gray(16), IEEEFP) => ColorType::L32F,
(tiff::ColorType::Gray(32), IEEEFP) => ColorType::L32F,
(tiff::ColorType::GrayA(8), Uint) => ColorType::La8,
(tiff::ColorType::GrayA(16), Uint) => ColorType::La16,
Expand All @@ -135,6 +136,8 @@ where
(tiff::ColorType::RGBA(16), Uint) => ColorType::Rgba16,
(tiff::ColorType::CMYK(8), Uint) => ColorType::Rgb8,
(tiff::ColorType::CMYK(16), Uint) => ColorType::Rgb16,
(tiff::ColorType::CMYK(16), IEEEFP) => ColorType::Rgb32F,
(tiff::ColorType::RGBA(16), IEEEFP) => ColorType::Rgba32F,
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(tiff::ColorType::RGB(32), IEEEFP) => ColorType::Rgb32F,
(tiff::ColorType::RGBA(32), IEEEFP) => ColorType::Rgba32F,
(tiff::ColorType::YCbCr(8), Uint) => ColorType::Rgb8,
Expand All @@ -152,6 +155,9 @@ where
(tiff::ColorType::CMYK(8), Uint) => ExtendedColorType::Cmyk8,
(tiff::ColorType::CMYK(16), Uint) => ExtendedColorType::Cmyk16,
(tiff::ColorType::YCbCr(8), Uint) => ExtendedColorType::YCbCr8,
(tiff::ColorType::Gray(16), IEEEFP) => ExtendedColorType::L16F,
(tiff::ColorType::CMYK(16), IEEEFP) => ExtendedColorType::Rgb16F,
(tiff::ColorType::RGBA(16), IEEEFP) => ExtendedColorType::Rgba16F,
_ => color_type.into(),
};

Expand Down Expand Up @@ -534,6 +540,18 @@ impl<R: BufRead + Seek> ImageDecoder for TiffDecoder<R> {

ycbcr_to_rgb8(ycbcr, lr, lg, lb, out);
}
DecodingResult::F16(v)
if matches!(
info.original_color_type,
ExtendedColorType::L16F
| ExtendedColorType::Rgb16F
| ExtendedColorType::Rgba16F
) =>
{
for (half, out) in v.iter().zip(buf.as_chunks_mut::<4>().0.iter_mut()) {
*out = half.to_f32().to_ne_bytes();
}
Comment on lines +535 to +537

@mhils mhils Jul 16, 2026

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Maybe a bit more intuitive:

Suggested change
for (half, out) in v.iter().zip(buf.as_chunks_mut::<4>().0.iter_mut()) {
*out = half.to_f32().to_ne_bytes();
}
for (out, f) in bytemuck::cast_slice_mut::<u8, f32>(buf).iter_mut().zip(v) {
*out = f.to_f32();
}

@RunDevelopment RunDevelopment Jul 16, 2026

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This is wrong, unfortunately. A slice of f32 must have an alignment requirement of 4, but the slice of u8 we have doesn't guarantee that. So bytemuck::cast_slice_mut will panic if the slice doesn't happen to be aligned to a multiple of 4. Users are allowed to give us slices of any alignment, so we have to be careful.

}
DecodingResult::U8(v) => {
buf.copy_from_slice(v);
}
Expand Down
19 changes: 18 additions & 1 deletion src/color.rs
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Expand Up @@ -153,7 +153,16 @@ pub enum ExtendedColorType {
/// Pixel is 8-bit BGR with an alpha channel
Bgra8,

// TODO f16 types?
// TODO: Should the new f16 types come after Ycbcr8 for serde backwards compatibility?
/// Pixel is 16-bit float luminance
L16F,
/// Pixel is 16-bit float luminance with an alpha channel
La16F,
/// Pixel is 16-bit float RGB
Rgb16F,
/// Pixel is 16-bit float RGBA
Rgba16F,

/// Pixel is 32-bit float luminance
L32F,
/// Pixel is 32-bit float luminance with an alpha channel
Expand Down Expand Up @@ -191,20 +200,23 @@ impl ExtendedColorType {
| ExtendedColorType::L4
| ExtendedColorType::L8
| ExtendedColorType::L16
| ExtendedColorType::L16F
| ExtendedColorType::L32F
| ExtendedColorType::Unknown(_) => 1,
ExtendedColorType::La1
| ExtendedColorType::La2
| ExtendedColorType::La4
| ExtendedColorType::La8
| ExtendedColorType::La16
| ExtendedColorType::La16F
| ExtendedColorType::La32F => 2,
ExtendedColorType::Rgb1
| ExtendedColorType::Rgb2
| ExtendedColorType::Rgb4
| ExtendedColorType::Rgb5x1
| ExtendedColorType::Rgb8
| ExtendedColorType::Rgb16
| ExtendedColorType::Rgb16F
| ExtendedColorType::Rgb32F
| ExtendedColorType::YCbCr8
| ExtendedColorType::Bgr8 => 3,
Expand All @@ -213,6 +225,7 @@ impl ExtendedColorType {
| ExtendedColorType::Rgba4
| ExtendedColorType::Rgba8
| ExtendedColorType::Rgba16
| ExtendedColorType::Rgba16F
| ExtendedColorType::Rgba32F
| ExtendedColorType::Bgra8
| ExtendedColorType::Cmyk8
Expand Down Expand Up @@ -246,6 +259,10 @@ impl ExtendedColorType {
ExtendedColorType::La16 => 32,
ExtendedColorType::Rgb16 => 48,
ExtendedColorType::Rgba16 => 64,
ExtendedColorType::L16F => 16,
ExtendedColorType::La16F => 32,
ExtendedColorType::Rgb16F => 48,
ExtendedColorType::Rgba16F => 64,
ExtendedColorType::L32F => 32,
ExtendedColorType::La32F => 64,
ExtendedColorType::Rgb32F => 96,
Expand Down
Binary file added tests/images/tiff/testsuite/random-fp16.tiff
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6 changes: 6 additions & 0 deletions tests/reference_images.rs
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Expand Up @@ -133,6 +133,12 @@ fn main() -> std::process::ExitCode {

if reference_format == ImageFormat::Png && image_format == Some(ImageFormat::Tiff) {
match test_img {
DynamicImage::ImageLuma32F(_) => {
test_img = test_img.to_luma16().into();
}
DynamicImage::ImageLumaA32F(_) => {
test_img = test_img.to_luma_alpha16().into();
}
DynamicImage::ImageRgb32F(_) => {
test_img = test_img.to_rgb16().into();
}
Expand Down
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