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Unify grayscale integer code paths

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RunDevelopment committed 2026-03-03 14:54:32 +01:00
1 parent 0a878888db
commit d872ff8751
1 file changed
+9 -26
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src/decoder/mod.rs
+9 -26
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@@ -717,36 +717,19 @@ fn invert_colors(
sample_format: SampleFormat,
) -> TiffResult<()> {
match (color_type, sample_format) {
// Where pixels do not cross a byte boundary
(ColorType::Gray(1 | 2 | 4 | 8), SampleFormat::Uint) => {
(ColorType::Gray(1 | 2 | 4 | 8 | 16 | 32 | 64), SampleFormat::Uint) => {
// It's guaranteed that pixels do not cross a byte boundary.
// To invert a single N-bit pixel, we can calculate:
// (2^N - 1) - x = (2^N - 1) + !x + 1 (because -x = !x + 1)
// = 2^n + !x
// = !x (because modular arithmetic)
//
// Further, since !x operates on bits independently, negating bytes
// also works for multi-byte pixels.
for x in buf {
// Equivalent to both of the following:
//
// *x = 0xff - *x
// *x = !*x
//
// since -x = !x+1
*x = !*x;
}
}
(ColorType::Gray(16), SampleFormat::Uint) => {
for x in buf.as_chunks_mut::<2>().0 {
let v = u16::from_ne_bytes(*x);
*x = (0xffff - v).to_ne_bytes();
}
}
(ColorType::Gray(32), SampleFormat::Uint) => {
for x in buf.as_chunks_mut::<4>().0 {
let v = u32::from_ne_bytes(*x);
*x = (0xffff_ffff - v).to_ne_bytes();
}
}
(ColorType::Gray(64), SampleFormat::Uint) => {
for x in buf.as_chunks_mut::<8>().0 {
let v = u64::from_ne_bytes(*x);
*x = (0xffff_ffff_ffff_ffff - v).to_ne_bytes();
}
}
(ColorType::Gray(32), SampleFormat::IEEEFP) => {
for x in buf.as_chunks_mut::<4>().0 {
let v = f32::from_ne_bytes(*x);