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filters.js
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filters.js
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Filters = {};
Filters.filterImage = function(filter, imageData, var_args) {
var args = [imageData];
for (var i=2; i<arguments.length; i++) {
args.push(arguments[i]);
}
return filter.apply(null, args);
};
Filters.grayscale = function(pixels, args) {
var d = pixels.data;
for (var i=0; i<d.length; i+=4) {
var r = d[i];
var g = d[i+1];
var b = d[i+2];
// CIE luminance for the RGB
// The human eye is bad at seeing red and blue, so we de-emphasize them.
var v = 0.2126*r + 0.7152*g + 0.0722*b;
d[i] = d[i+1] = d[i+2] = v
}
return pixels;
};
Filters.brightness = function(pixels, adjustment) {
var d = pixels.data;
for (var i=0; i<d.length; i+=4) {
d[i] += adjustment;
d[i+1] += adjustment;
d[i+2] += adjustment;
}
return pixels;
};
Filters.threshold = function(pixels, threshold) {
var d = pixels.data;
for (var i=0; i<d.length; i+=4) {
var r = d[i];
var g = d[i+1];
var b = d[i+2];
var v = (0.2126*r + 0.7152*g + 0.0722*b >= threshold) ? 255 : 0;
d[i] = d[i+1] = d[i+2] = v
}
return pixels;
};
Filters.createImageData = function(w,h) {
Filters.tmpCanvas = document.querySelector('#canv2')
Filters.tmpCtx = Filters.tmpCanvas.getContext('2d');
//console.log(Filters.tmpCanvas);
return this.tmpCtx.createImageData(w,h);
};
Filters.convolute = function(pixels, weights, opaque) {
var side = Math.round(Math.sqrt(weights.length));
var halfSide = Math.floor(side/2);
var src = pixels.data;
var sw = pixels.width;
var sh = pixels.height;
// pad output by the convolution matrix
var w = sw;
var h = sh;
var output = Filters.createImageData(w, h);
var dst = output.data;
// go through the destination image pixels
var alphaFac = opaque ? 1 : 0;
for (var y=0; y<h; y++) {
for (var x=0; x<w; x++) {
var sy = y;
var sx = x;
var dstOff = (y*w+x)*4;
// calculate the weighed sum of the source image pixels that
// fall under the convolution matrix
var r=0, g=0, b=0, a=0;
for (var cy=0; cy<side; cy++) {
for (var cx=0; cx<side; cx++) {
var scy = sy + cy - halfSide;
var scx = sx + cx - halfSide;
if (scy >= 0 && scy < sh && scx >= 0 && scx < sw) {
var srcOff = (scy*sw+scx)*4;
var wt = weights[cy*side+cx];
r += src[srcOff] * wt;
g += src[srcOff+1] * wt;
b += src[srcOff+2] * wt;
a += src[srcOff+3] * wt;
}
}
}
dst[dstOff] = r;
dst[dstOff+1] = g;
dst[dstOff+2] = b;
dst[dstOff+3] = a + alphaFac*(255-a);
// console.log(sx);
}
}
return output;
};