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fix: CLAHE tile size and alpha channel corruption in image enhancement

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CLAHE width/height is tile size in pixels, not tile count. A 3px tile on
a 992x1088 image created ~330x360 independent histogram regions, producing
crosshatch/etching artifacts. Now uses image_dimension/8 (clamped 8-256)
for ~8 tiles per axis. Also strips alpha before enhancement and re-joins
after to prevent CLAHE/normalise/linear from corrupting transparency.
This commit is contained in:
SnapOtter
2026-05-09 15:20:55 +08:00
parent 7f131d99a6
commit 7b1f09f5d0
3 changed files with 100 additions and 4 deletions
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packages/image-engine/src/operations/auto-enhance.ts
+6 -4
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@@ -226,10 +226,12 @@ export function applyCorrections(
// maxSlope must be an integer (Sharp requirement); skip for tiny images
if (toggles.contrast !== false) {
const maxSlope = clamp(Math.round(1.0 + (intensity / 100) * 4.0 * presets.clahe), 1, 10);
const minDim = imageSize ? Math.min(imageSize.width, imageSize.height) : 4;
const tileSize = minDim >= 3 ? 3 : 1;
if (maxSlope >= 2) {
result = result.clahe({ width: tileSize, height: tileSize, maxSlope });
const w = imageSize?.width ?? 64;
const h = imageSize?.height ?? 64;
const tileW = clamp(Math.round(w / 8), 8, 256);
const tileH = clamp(Math.round(h / 8), 8, 256);
if (maxSlope >= 2 && w >= tileW && h >= tileH) {
result = result.clahe({ width: tileW, height: tileH, maxSlope });
}
}