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var patterns = {}
patterns[2] = [ 0, 2,
3, 1 ]
patterns[3] = [ 0, 5, 3,
8, 1, 6,
4, 7, 2, ]
patterns[4] = [ 0, 8, 2, 10,
6, 14, 4, 12,
3, 11, 1, 9,
5, 13, 7, 15 ]
CanvasQuery.Wrapper.prototype.threshold = function(factor) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
if (factor < 1) factor *= 255
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / 3
var lum = val > factor ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
CanvasQuery.Wrapper.prototype.randomDither = function() {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / (3*255)
var lum = val > Math.random() ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
CanvasQuery.Wrapper.prototype.pattern2Dither = function() {
this.patternDither(2)
}
CanvasQuery.Wrapper.prototype.pattern3Dither = function() {
this.patternDither(3)
}
CanvasQuery.Wrapper.prototype.pattern4Dither = function() {
this.patternDither(4)
}
CanvasQuery.Wrapper.prototype.patternDither = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
var pat = patterns[n]
var len = pat.length - 1
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var p = ((i % n) * n) + (j % n)
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / (3*255)
var lum = val > pat[p]/len ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
CanvasQuery.Wrapper.prototype.pattern2LiteDither = function() {
this.patternLiteDither(2)
}
CanvasQuery.Wrapper.prototype.pattern3LiteDither = function() {
this.patternLiteDither(3)
}
CanvasQuery.Wrapper.prototype.pattern4LiteDither = function() {
this.patternLiteDither(4)
}
CanvasQuery.Wrapper.prototype.patternLiteDither = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var width = this.canvas.width
var height = this.canvas.height
var pat = patterns[n]
var len = pat.length
for (var i = 0; i < height; i++) {
for (var j = 0; j < width; j++) {
var p = ((i % n) * n) + (j % n)
var a = 4 * (i*width + j)
var val = (bitmapData[a] + bitmapData[a+1] + bitmapData[a+2]) / (3*255)
var lum = val > pat[p]/len ? 255 : 0
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
CanvasQuery.Wrapper.prototype.floydSteinbergDither = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var mask = this.grayscaleToMask()
var width = this.canvas.width
var height = this.canvas.height
for (var y = 0; y < height; y++) {
for (var x = 0; x < width; x++) {
var p = (y*width + x)
var a = 4 * p
var val = mask[p]
var lum = val > 127 ? 255 : 0
var error = val - lum
if (x < width-1)
mask[ (y*width) + x+1 ] += 7/16 * error
if (y < height-1 && x > 0)
mask[ ((y+1)*width) + x-1 ] += 5/16 * error
if (y < height-1)
mask[ ((y+1)*width) + x ] += 3/16 * error
if (y < height-1 && x < width-1)
mask[ ((y+1)*width) + x+1 ] += 1/16 * error
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
CanvasQuery.Wrapper.prototype.rightDither = function(n) {
var bitmap = this.context.getImageData(0, 0, this.canvas.width, this.canvas.height)
var bitmapData = bitmap.data
var mask = this.grayscaleToMask()
var width = this.canvas.width
var height = this.canvas.height
for (var y = 0; y < height; y++) {
for (var x = 0; x < width; x++) {
var p = (y*width + x)
var a = 4 * p
var val = mask[p]
var lum = val > 127 ? 255 : 0
var error = val - lum
if (x < width-1)
mask[ (y*width) + x+1 ] += 7/16 * error
bitmapData[a] = bitmapData[a+1] = bitmapData[a+2] = lum
}
}
this.context.putImageData(bitmap, 0, 0);
return this;
}
CanvasQuery.Wrapper.prototype.halftone = function(radius, angle) {
var mask = this.grayscaleToMask()
this.fillStyle("#fff")
this.fillRect(0, 0, this.canvas.width, this.canvas.height)
var diameter = radius*2
var TWO_PI = Math.PI*2
var angle = angle / 180 * Math.PI
var cos = Math.cos(angle)
var sin = Math.sin(angle)
var xstep = cos * radius
var ystep = sin * radius
var w = this.canvas.width
var h = this.canvas.height
this.fillStyle("#000")
for (var i = -w; i < w; i++) {
for (var j = -h; j < h; j++) {
var x = i * ystep - j * xstep
var y = i * xstep + j * ystep
if (x > -diameter && y > -diameter && x < w+diameter && y < h+diameter) {
circle(this,x,y)
}
}
}
function circle(cq,x,y) {
var xx = x < 0 ? 0 : x > w ? w - 1 : x;
var yy = y < 0 ? 0 : y > h ? h - 1 : y;
var r = (1 - Math.pow( mask[ ~~(~~yy*w+(xx)) ] / 255, Math.E/4 )) * radius
cq.beginPath()
.arc(x,y,r,0,TWO_PI)
.closePath()
.fill();
}
return this;
}
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