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chore: fix Clippy lint, very slightly optimize optimize_alpha function

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Alejandro González 2025-09-20 13:20:14 +02:00
parent 82cae58794
commit 2a3aa83928
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1 changed files with 19 additions and 2 deletions
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21
src/filters.rs
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@ -163,11 +163,28 @@ impl RowFilter {
.unwrap_or(i),
_ => i - 1,
};
// These assertions help eliminate a few bounds checks in the slice accesses below
assert!(prev < pixels.len());
assert!(i < prev_pixels.len());
match self {
Self::None => unreachable!(),
Self::Sub => {
for j in 0..color_bytes {
pixels[i][j] = pixels[prev][j];
// The code below is roughly equivalent to pixels[i][0..color_bytes].copy_from_slice(&pixels[prev][0..color_bytes]),
// if such a thing was possible to do without violating Rust aliasing rules. See:
// https://users.rust-lang.org/t/problem-borrowing-two-elements-of-vec-mutably/21446/2
if prev < i {
let (pixels_head, pixels_tail) = pixels.split_at_mut(prev + 1);
pixels_tail[i - prev - 1][0..color_bytes]
.copy_from_slice(&pixels_head[prev][0..color_bytes]);
} else if prev > i {
let (pixels_head, pixels_tail) = pixels.split_at_mut(i + 1);
pixels_head[i][0..color_bytes]
.copy_from_slice(&pixels_tail[prev - i - 1][0..color_bytes]);
} else {
// If prev == i, we'd be copying the pixels onto themselves, which is useless
}
}
Self::Up => {