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46 lines
1.6 KiB
JavaScript
46 lines
1.6 KiB
JavaScript
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module.exports = (ctx, canvas, matrix, opaque) => {
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const side = Math.round(Math.sqrt(matrix.length));
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const halfSide = Math.floor(side / 2);
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const pixels = ctx.getImageData(0, 0, canvas.width, canvas.height);
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const src = pixels.data;
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const sw = pixels.width;
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const sh = pixels.height;
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const w = sw;
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const h = sh;
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const output = ctx.getImageData(0, 0, canvas.width, canvas.height);
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const dst = output.data;
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const alphaFac = opaque ? 1 : 0;
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for (let y = 0; y < h; y++) {
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for (let x = 0; x < w; x++) {
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const sy = y;
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const sx = x;
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const dstOff = (y * w + x) * 4;
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let r = 0;
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let g = 0;
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let b = 0;
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let a = 0;
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for (let cy = 0; cy < side; cy++) {
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for (let cx = 0; cx < side; cx++) {
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const scy = sy + cy - halfSide;
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const scx = sx + cx - halfSide;
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if (scy >= 0 && scy < sh && scx >= 0 && scx < sw) {
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const srcOff = (scy * sw + scx) * 4;
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const wt = matrix[cy * side + cx];
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r += src[srcOff] * wt;
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g += src[srcOff + 1] * wt;
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b += src[srcOff + 2] * wt;
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a += src[srcOff + 3] * wt;
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}
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}
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}
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dst[dstOff] = r;
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dst[dstOff + 1] = g;
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dst[dstOff + 2] = b;
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dst[dstOff + 3] = a + alphaFac * (255 - a);
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}
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}
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ctx.putImageData(output, 0, 0);
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return ctx;
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};
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