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zazaulola/floyd-steinberg.js

Created July 20, 2024 05:38
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Grayscale image halftone dithering
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floyd-steinberg.js
onmessage = ({ data: { data, width, height } }) => {
const add = (d, i, v) => {
if (i >= d.length) return;
d[i] += v;
};
const w = width * 4;
let i = 0;
for (let y = 0; y < height; y++) {
for (let x = 0; x < width; x++, i += 4) {
const curPixel = data[i];
const newPixel = curPixel < 129 ? 0 : 255;
const err = (curPixel - newPixel) / 16;
data[i + 0] = newPixel;
data[i + 1] = newPixel;
data[i + 2] = newPixel;
add(data, i + 4, err * 7);
add(data, i + w - 4, err * 3);
add(data, i + w, err * 5);
add(data, i + w + 4, err);
}
}
postMessage(data);
};
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