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23 lines
1.3 KiB
23 lines
1.3 KiB
9 years ago
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module.exports = function desaturate(image){
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var width, height;
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if(image.data){
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var src = image.data;
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width = image.width, height = image.height;
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var dst = new Uint8Array(width * height);
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var srcLength = src.length | 0, srcLength_16 = (srcLength - 16) | 0;
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for (var i = 0, j = 0; i <= srcLength_16; i += 16, j += 4) {
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// convert to grayscale 4 pixels at a time; eveything with alpha gets put in front of 50% gray
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dst[j] = (((src[i] * 77 + src[i+1] * 151 + src[i+2] * 28) * src[i+3]) + ((255-src[i+3]) << 15) + 32768) >> 16
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dst[j+1] = (((src[i+4] * 77 + src[i+5] * 151 + src[i+6] * 28) * src[i+7]) + ((255-src[i+7]) << 15) + 32768) >> 16
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dst[j+2] = (((src[i+8] * 77 + src[i+9] * 151 + src[i+10] * 28) * src[i+11]) + ((255-src[i+11]) << 15) + 32768) >> 16
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dst[j+3] = (((src[i+12] * 77 + src[i+13] * 151 + src[i+14] * 28) * src[i+15]) + ((255-src[i+15]) << 15) + 32768) >> 16
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}
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for (; i < srcLength; i += 4, ++j) //finish up
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dst[j] = (((src[i] * 77 + src[i+1] * 151 + src[i+2] * 28) * src[i+3]) + ((255-src[i+3]) << 15) + 32768) >> 16
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image = dst;
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} else {
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throw 'Expected ImageData'
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}
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return image
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}
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