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Use most popular color as first for mzeng and battiato

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This commit is contained in:
Andrew 2024-04-02 20:34:00 +13:00
parent c88a67a2ca
commit 3a387b3eca
1 changed files with 25 additions and 6 deletions
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31
src/reduction/palette.rs
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@ -145,7 +145,7 @@ pub fn sorted_palette_mzeng(png: &PngImage) -> Option<PngImage> {
let edges = weighted_edges(&matrix); let edges = weighted_edges(&matrix);
let mut remapping = mzeng_reindex(palette.len(), edges, &matrix); let mut remapping = mzeng_reindex(palette.len(), edges, &matrix);
apply_most_popular_edge_color(png, &mut remapping); apply_most_popular_color(png, &mut remapping);
apply_palette_reorder(png, &remapping) apply_palette_reorder(png, &remapping)
} }
@ -167,7 +167,7 @@ pub fn sorted_palette_battiato(png: &PngImage) -> Option<PngImage> {
let edges = weighted_edges(&matrix); let edges = weighted_edges(&matrix);
let mut remapping = battiato_reindex(palette.len(), edges); let mut remapping = battiato_reindex(palette.len(), edges);
apply_most_popular_edge_color(png, &mut remapping); apply_most_popular_color(png, &mut remapping);
apply_palette_reorder(png, &remapping) apply_palette_reorder(png, &remapping)
} }
@ -222,10 +222,29 @@ fn most_popular_edge_color(num_colors: usize, png: &PngImage) -> usize {
.0 .0
} }
// Put the most popular edge color first, which can help slightly if the filter bytes are 0 // Find the most popular color in the image, along with its count
fn apply_most_popular_edge_color(png: &PngImage, remapping: &mut [usize]) { fn most_popular_color(num_colors: usize, png: &PngImage) -> (usize, u32) {
let keep_first = most_popular_edge_color(remapping.len(), png); let mut counts = [0u32; 256];
let first_idx = remapping.iter().position(|&i| i == keep_first).unwrap(); for &val in &png.data {
counts[val as usize] += 1;
}
counts
.iter()
.copied()
.take(num_colors)
.enumerate()
.max_by_key(|&(_, v)| v)
.unwrap_or_default()
}
// Put the most popular color first
fn apply_most_popular_color(png: &PngImage, remapping: &mut [usize]) {
let most_popular = most_popular_color(remapping.len(), png);
// If the most popular color is less than 15% of the image, don't use it
if most_popular.1 < png.data.len() as u32 * 3 / 20 {
return;
}
let first_idx = remapping.iter().position(|&i| i == most_popular.0).unwrap();
// If the index is past halfway, reverse the order so as to minimize the change // If the index is past halfway, reverse the order so as to minimize the change
if first_idx >= remapping.len() / 2 { if first_idx >= remapping.len() / 2 {
remapping.reverse(); remapping.reverse();