Created
November 22, 2014 00:16
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(function(global) { | |
function Dither(container, width, height) { | |
this.container = container; | |
this.width = width; | |
this.height = height; | |
this.canvas = null; | |
this.image = null; | |
this.draw = this.draw.bind(this); | |
this.handleSliderChange = this.handleSliderChange.bind(this); | |
this.handleDragOver = this.handleDragOver.bind(this); | |
this.handleDrop = this.handleDrop.bind(this); | |
} | |
Dither.prototype.init = function() { | |
this.canvas = this.container.ownerDocument.createElement('canvas'); | |
this.canvas.width = this.width; | |
this.canvas.height = this.height; | |
this.canvas.addEventListener('dragover', this.handleDragOver, true); | |
this.canvas.addEventListener('drop', this.handleDrop, true); | |
this.canvas.style.outline = '1px outset #ccc'; | |
this.slider = this.container.ownerDocument.createElement('input'); | |
this.slider.type = 'range'; | |
this.slider.min = 2; | |
this.slider.max = 16; | |
this.slider.value = 2; | |
this.slider.addEventListener('change', this.handleSliderChange); | |
this.container.appendChild(this.canvas); | |
this.container.appendChild(this.slider); | |
}; | |
Dither.prototype.loadImage = function(file) { | |
this.image = new Image; | |
this.image.src = URL.createObjectURL(file); | |
this.image.onload = this.draw; | |
} | |
Dither.prototype.draw = function() { | |
var ctx = this.canvas.getContext('2d'); | |
ctx.drawImage(this.image, 0, 0, this.width, this.height); | |
var pixels = ctx.getImageData(0, 0, this.width, this.height); | |
for (var j = 0; j < this.height - 1; j++) { | |
for (var i = 0; i < this.width - 1; i++) { | |
var idx = 4 * (j * this.height + i), | |
r = pixels[idx], | |
g = pixels[idx+1], | |
b = pixels[idx+2], | |
l = this.constructor.luma(r, g, b), | |
v = Math.round(Math.round((l / 255) * this.slider.value) / this.slider.value * 255); | |
pixels[idx] = pixels[idx + 1] = pixels[idx + 2] = v; | |
} | |
} | |
ctx.putImageData(pixels, 0, 0); | |
}; | |
Dither.prototype.handleSliderChange = function(ev) { | |
this.draw(); | |
}; | |
Dither.prototype.handleDragOver = function(ev) { | |
ev.preventDefault(); | |
}; | |
Dither.prototype.handleDrop = function(ev){ | |
ev.preventDefault(); | |
this.loadImage(ev.dataTransfer.files[0]); | |
}; | |
Dither.luma = function(r, g, b) { | |
return Math.round(0.2126 * r + 0.7152 * g + 0.0722 * b); | |
}; | |
global.Dither = Dither; | |
})(this); |
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