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added histogram equalization

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This commit is contained in:
Peihong Guo 2013-11-28 03:14:22 -06:00
parent eaacd74ea9
commit b731aed0a9
2 changed files with 53 additions and 0 deletions
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5
index.html
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@ -143,6 +143,11 @@
options : {
blockSize : 8
}
},
{
effect : 'equalize',
options : {
}
}
];

48
pixastic.effects.js
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@ -1222,6 +1222,54 @@ Pixastic.Effects = (function() {
}
y0 = y1;
}
},
equalize : function(inData, outData, width, height, options, progress) {
var n = width * height, p, i, level, ratio,
prog, lastProg;
var round = Math.round;
// build histogram
var pdf = new Array(256);
for (i=0;i<256;i++) {
pdf[i] = 0;
}
for (i=0;i<n;i++) {
p = i * 4;
level = clamp(round(inData[p] * 0.3 + inData[p+1] * 0.59 + inData[p+2] * 0.11), 0, 255);
outData[p+3] = level;
pdf[ level ]++;
}
// build cdf
var cdf = new Array(256);
cdf[0] = pdf[0];
for(i=1;i<256;i++) {
cdf[i] = cdf[i-1] + pdf[i];
}
// normalize cdf
for(i=0;i<256;i++) {
cdf[i] = cdf[i] / n * 255.0;
}
// map the pixel values
for (i=0;i<n;i++) {
p = i * 4;
level = outData[p+3];
ratio = cdf[level] / (level || 1);
outData[p] = clamp(round(inData[p] * ratio), 0, 255);
outData[p+1] = clamp(round(inData[p+1] * ratio), 0, 255);
outData[p+2] = clamp(round(inData[p+2] * ratio), 0, 255);
outData[p+3] = inData[p+3];
if (progress) {
prog = (i/n*100 >> 0) / 100;
if (prog > lastProg) {
lastProg = progress(prog);
}
}
}
}
};