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fix not being able to use floydsteinberg dithering

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javl
2023-05-02 12:43:19 +02:00
parent a7decafb85
commit 1f8e7f9548
1 changed files with 8 additions and 2 deletions
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dithering.js
+8 -2
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@@ -11,7 +11,7 @@ const bwPalette = [
function dithering(ctx, width, height, threshold, typeIndex) {
const type = ['binary', 'bayer', 'floysteinberg', 'atkinson'][typeIndex];
const type = ['binary', 'bayer', 'floydsteinberg', 'atkinson'][typeIndex];
const bayerThresholdMap = [
[ 15, 135, 45, 165 ],
[ 195, 75, 225, 105 ],
@@ -43,12 +43,14 @@ function dithering(ctx, width, height, threshold, typeIndex) {
if (type ==="binary") {
// No dithering
imageData.data[currentPixel] = imageData.data[currentPixel] < threshold ? 0 : 255;
} else if (type ==="bayer") {
// 4x4 Bayer ordered dithering algorithm
var x = currentPixel/4 % w;
var y = Math.floor(currentPixel/4 / w);
var map = Math.floor( (imageData.data[currentPixel] + bayerThresholdMap[x%4][y%4]) / 2 );
imageData.data[currentPixel] = (map < threshold) ? 0 : 255;
} else if (type ==="floydsteinberg") {
// Floyda€"Steinberg dithering algorithm
newPixel = imageData.data[currentPixel] < 129 ? 0 : 255;
@@ -59,7 +61,8 @@ function dithering(ctx, width, height, threshold, typeIndex) {
imageData.data[currentPixel + 4*w - 4 ] += err*3;
imageData.data[currentPixel + 4*w ] += err*5;
imageData.data[currentPixel + 4*w + 4 ] += err*1;
} else {
} else if (type ==="atkinson") {
// Bill Atkinson's dithering algorithm
newPixel = imageData.data[currentPixel] < threshold ? 0 : 255;
err = Math.floor((imageData.data[currentPixel] - newPixel) / 8);
@@ -71,6 +74,9 @@ function dithering(ctx, width, height, threshold, typeIndex) {
imageData.data[currentPixel + 4*w ] += err;
imageData.data[currentPixel + 4*w + 4 ] += err;
imageData.data[currentPixel + 8*w ] += err;
} else {
console.error("unknown dithering type requested: " + type);
}
// Set g and b pixels equal to r