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Fix bKGD conversion from gray to palette

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This commit is contained in:
Andrew 2023-05-03 21:47:08 +12:00
parent a26d225d81
commit d6cc8a003b
2 changed files with 29 additions and 15 deletions
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42
src/reduction/color.rs
View file

@ -98,22 +98,36 @@ pub fn reduce_to_palette(png: &PngImage) -> Option<PngImage> {
let mut aux_headers = png.aux_headers.clone();
if let Some(bkgd_header) = png.aux_headers.get(b"bKGD") {
if bkgd_header.len() != 6 {
// malformed chunk?
return None;
}
// In bKGD 16-bit values are used even for 8-bit images
let bg = RGBA8::new(bkgd_header[1], bkgd_header[3], bkgd_header[5], 255);
let entry = if let Some(&entry) = palette.get(&bg) {
entry
} else if palette.len() < 256 {
let entry = palette.len() as u8;
palette.insert(bg, entry);
entry
let bg = if png.ihdr.color_type.is_rgb() && bkgd_header.len() == 6 {
// In bKGD 16-bit values are used even for 8-bit images
Some(RGBA8::new(
bkgd_header[1],
bkgd_header[3],
bkgd_header[5],
255,
))
} else if png.ihdr.color_type == ColorType::GrayscaleAlpha && bkgd_header.len() == 2 {
Some(RGBA8::new(
bkgd_header[1],
bkgd_header[1],
bkgd_header[1],
255,
))
} else {
return None; // No space in palette to store the bg as an index
None
};
aux_headers.insert(*b"bKGD", vec![entry]);
if let Some(bg) = bg {
let entry = if let Some(&entry) = palette.get(&bg) {
entry
} else if palette.len() < 256 {
let entry = palette.len() as u8;
palette.insert(bg, entry);
entry
} else {
return None; // No space in palette to store the bg as an index
};
aux_headers.insert(*b"bKGD", vec![entry]);
}
}
if let Some(sbit_header) = png.aux_headers.get(b"sBIT") {

2
tests/regression.rs
View file

@ -243,7 +243,7 @@ fn issue_60() {
None,
RGBA,
BitDepth::Eight,
GRAYSCALE_ALPHA,
RGBA,
BitDepth::Eight,
);
}