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Javascript function for sharpening images.
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function sharpen(ctx, w, h, mix) { | |
var x, sx, sy, r, g, b, a, dstOff, srcOff, wt, cx, cy, scy, scx, | |
weights = [0, -1, 0, -1, 5, -1, 0, -1, 0], | |
katet = Math.round(Math.sqrt(weights.length)), | |
half = (katet * 0.5) | 0, | |
dstData = ctx.createImageData(w, h), | |
dstBuff = dstData.data, | |
srcBuff = ctx.getImageData(0, 0, w, h).data, | |
y = h; | |
while (y--) { | |
x = w; | |
while (x--) { | |
sy = y; | |
sx = x; | |
dstOff = (y * w + x) * 4; | |
r = 0; | |
g = 0; | |
b = 0; | |
a = 0; | |
for (cy = 0; cy < katet; cy++) { | |
for (cx = 0; cx < katet; cx++) { | |
scy = sy + cy - half; | |
scx = sx + cx - half; | |
if (scy >= 0 && scy < h && scx >= 0 && scx < w) { | |
srcOff = (scy * w + scx) * 4; | |
wt = weights[cy * katet + cx]; | |
r += srcBuff[srcOff] * wt; | |
g += srcBuff[srcOff + 1] * wt; | |
b += srcBuff[srcOff + 2] * wt; | |
a += srcBuff[srcOff + 3] * wt; | |
} | |
} | |
} | |
dstBuff[dstOff] = r * mix + srcBuff[dstOff] * (1 - mix); | |
dstBuff[dstOff + 1] = g * mix + srcBuff[dstOff + 1] * (1 - mix); | |
dstBuff[dstOff + 2] = b * mix + srcBuff[dstOff + 2] * (1 - mix); | |
dstBuff[dstOff + 3] = srcBuff[dstOff + 3]; | |
} | |
} | |
ctx.putImageData(dstData, 0, 0); | |
} |
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