Created
April 3, 2013 22:12
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pure Javascript PNG parser
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(function() { | |
/* | |
# MIT LICENSE | |
# Copyright (c) 2011 Devon Govett | |
# | |
# Permission is hereby granted, free of charge, to any person obtaining a copy of this | |
# software and associated documentation files (the "Software"), to deal in the Software | |
# without restriction, including without limitation the rights to use, copy, modify, merge, | |
# publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons | |
# to whom the Software is furnished to do so, subject to the following conditions: | |
# | |
# The above copyright notice and this permission notice shall be included in all copies or | |
# substantial portions of the Software. | |
# | |
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING | |
# BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | |
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, | |
# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | |
*/ | |
var PNG; | |
PNG = (function() { | |
var APNG_BLEND_OP_OVER, APNG_BLEND_OP_SOURCE, APNG_DISPOSE_OP_BACKGROUND, APNG_DISPOSE_OP_NONE, APNG_DISPOSE_OP_PREVIOUS, makeImage, scratchCanvas, scratchCtx; | |
PNG.load = function(url, canvas, callback) { | |
var xhr; | |
var _this = this; | |
if (typeof canvas === 'function') callback = canvas; | |
xhr = new XMLHttpRequest; | |
xhr.open("GET", url, true); | |
xhr.responseType = "arraybuffer"; | |
xhr.onload = function() { | |
var data, png; | |
data = new Uint8Array(xhr.response || xhr.mozResponseArrayBuffer); | |
png = new PNG(data); | |
if (typeof (canvas != null ? canvas.getContext : void 0) === 'function') { | |
png.render(canvas); | |
} | |
return typeof callback === "function" ? callback(png) : void 0; | |
}; | |
return xhr.send(null); | |
}; | |
PNG.binload = function(base64_string, canvas, callback) { | |
var xhr; | |
var _this = this; | |
if (typeof canvas === 'function') callback = canvas; | |
var data, png; | |
data = Base64Binary.decode(base64_string); | |
png = new PNG(data); | |
if (typeof (canvas != null ? canvas.getContext : void 0) === 'function') { | |
png.render(canvas); | |
} | |
return typeof callback === "function" ? callback(png) : void 0; | |
}; | |
APNG_DISPOSE_OP_NONE = 0; | |
APNG_DISPOSE_OP_BACKGROUND = 1; | |
APNG_DISPOSE_OP_PREVIOUS = 2; | |
APNG_BLEND_OP_SOURCE = 0; | |
APNG_BLEND_OP_OVER = 1; | |
function PNG(data) { | |
var chunkSize, colors, delayDen, delayNum, frame, i, index, key, section, _short, text, _ref; | |
this.data = data; | |
this.pos = 8; | |
this.palette = []; | |
this.imgData = []; | |
this.transparency = {}; | |
this.animation = null; | |
this.text = {}; | |
frame = null; | |
while (true) { | |
chunkSize = this.readUInt32(); | |
section = ((function() { | |
var _results; | |
_results = []; | |
for (i = 0; i < 4; i++) { | |
_results.push(String.fromCharCode(this.data[this.pos++])); | |
} | |
return _results; | |
}).call(this)).join(''); | |
switch (section) { | |
case 'IHDR': | |
this.width = this.readUInt32(); | |
this.height = this.readUInt32(); | |
this.bits = this.data[this.pos++]; | |
this.colorType = this.data[this.pos++]; | |
this.compressionMethod = this.data[this.pos++]; | |
this.filterMethod = this.data[this.pos++]; | |
this.interlaceMethod = this.data[this.pos++]; | |
break; | |
case 'acTL': | |
this.animation = { | |
numFrames: this.readUInt32(), | |
numPlays: this.readUInt32() || Infinity, | |
frames: [] | |
}; | |
break; | |
case 'PLTE': | |
this.palette = this.read(chunkSize); | |
break; | |
case 'fcTL': | |
if (frame) this.animation.frames.push(frame); | |
this.pos += 4; | |
frame = { | |
width: this.readUInt32(), | |
height: this.readUInt32(), | |
xOffset: this.readUInt32(), | |
yOffset: this.readUInt32() | |
}; | |
delayNum = this.readUInt16(); | |
delayDen = this.readUInt16() || 100; | |
frame.delay = 1000 * delayNum / delayDen; | |
frame.disposeOp = this.data[this.pos++]; | |
frame.blendOp = this.data[this.pos++]; | |
frame.data = []; | |
break; | |
case 'IDAT': | |
case 'fdAT': | |
if (section === 'fdAT') { | |
this.pos += 4; | |
chunkSize -= 4; | |
} | |
data = (frame != null ? frame.data : void 0) || this.imgData; | |
for (i = 0; 0 <= chunkSize ? i < chunkSize : i > chunkSize; 0 <= chunkSize ? i++ : i--) { | |
data.push(this.data[this.pos++]); | |
} | |
break; | |
case 'tRNS': | |
this.transparency = {}; | |
switch (this.colorType) { | |
case 3: | |
this.transparency.indexed = this.read(chunkSize); | |
_short = 255 - this.transparency.indexed.length; | |
if (_short > 0) { | |
for (i = 0; 0 <= _short ? i < _short : i > _short; 0 <= _short ? i++ : i--) { | |
this.transparency.indexed.push(255); | |
} | |
} | |
break; | |
case 0: | |
this.transparency.grayscale = this.read(chunkSize)[0]; | |
break; | |
case 2: | |
this.transparency.rgb = this.read(chunkSize); | |
} | |
break; | |
case 'tEXt': | |
text = this.read(chunkSize); | |
index = text.indexOf(0); | |
key = String.fromCharCode.apply(String, text.slice(0, index)); | |
this.text[key] = String.fromCharCode.apply(String, text.slice(index + 1)); | |
break; | |
case 'IEND': | |
if (frame) this.animation.frames.push(frame); | |
this.colors = (function() { | |
switch (this.colorType) { | |
case 0: | |
case 3: | |
case 4: | |
return 1; | |
case 2: | |
case 6: | |
return 3; | |
} | |
}).call(this); | |
this.hasAlphaChannel = (_ref = this.colorType) === 4 || _ref === 6; | |
colors = this.colors + (this.hasAlphaChannel ? 1 : 0); | |
this.pixelBitlength = this.bits * colors; | |
this.colorSpace = (function() { | |
switch (this.colors) { | |
case 1: | |
return 'DeviceGray'; | |
case 3: | |
return 'DeviceRGB'; | |
} | |
}).call(this); | |
this.imgData = new Uint8Array(this.imgData); | |
return; | |
default: | |
this.pos += chunkSize; | |
} | |
this.pos += 4; | |
} | |
return; | |
} | |
PNG.prototype.read = function(bytes) { | |
var i, _results; | |
_results = []; | |
for (i = 0; 0 <= bytes ? i < bytes : i > bytes; 0 <= bytes ? i++ : i--) { | |
_results.push(this.data[this.pos++]); | |
} | |
return _results; | |
}; | |
PNG.prototype.readUInt32 = function() { | |
var b1, b2, b3, b4; | |
b1 = this.data[this.pos++] << 24; | |
b2 = this.data[this.pos++] << 16; | |
b3 = this.data[this.pos++] << 8; | |
b4 = this.data[this.pos++]; | |
return b1 | b2 | b3 | b4; | |
}; | |
PNG.prototype.readUInt16 = function() { | |
var b1, b2; | |
b1 = this.data[this.pos++] << 8; | |
b2 = this.data[this.pos++]; | |
return b1 | b2; | |
}; | |
PNG.prototype.decodePixels = function(data) { | |
var _byte, c, col, i, left, length, p, pa, paeth, pb, pc, pixelBytes, pixels, pos, row, scanlineLength, upper, upperLeft; | |
if (data == null) data = this.imgData; | |
if (data.length === 0) return new Uint8Array(0); | |
data = new FlateStream(data); | |
data = data.getBytes(); | |
pixelBytes = this.pixelBitlength / 8; | |
scanlineLength = pixelBytes * this.width; | |
pixels = new Uint8Array(scanlineLength * this.height); | |
length = data.length; | |
row = 0; | |
pos = 0; | |
c = 0; | |
while (pos < length) { | |
switch (data[pos++]) { | |
case 0: | |
for (i = 0; i < scanlineLength; i += 1) { | |
pixels[c++] = data[pos++]; | |
} | |
break; | |
case 1: | |
for (i = 0; i < scanlineLength; i += 1) { | |
_byte = data[pos++]; | |
left = i < pixelBytes ? 0 : pixels[c - pixelBytes]; | |
pixels[c++] = (_byte + left) % 256; | |
} | |
break; | |
case 2: | |
for (i = 0; i < scanlineLength; i += 1) { | |
_byte = data[pos++]; | |
col = (i - (i % pixelBytes)) / pixelBytes; | |
upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)]; | |
pixels[c++] = (upper + _byte) % 256; | |
} | |
break; | |
case 3: | |
for (i = 0; i < scanlineLength; i += 1) { | |
_byte = data[pos++]; | |
col = (i - (i % pixelBytes)) / pixelBytes; | |
left = i < pixelBytes ? 0 : pixels[c - pixelBytes]; | |
upper = row && pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)]; | |
pixels[c++] = (_byte + Math.floor((left + upper) / 2)) % 256; | |
} | |
break; | |
case 4: | |
for (i = 0; i < scanlineLength; i += 1) { | |
_byte = data[pos++]; | |
col = (i - (i % pixelBytes)) / pixelBytes; | |
left = i < pixelBytes ? 0 : pixels[c - pixelBytes]; | |
if (row === 0) { | |
upper = upperLeft = 0; | |
} else { | |
upper = pixels[(row - 1) * scanlineLength + col * pixelBytes + (i % pixelBytes)]; | |
upperLeft = col && pixels[(row - 1) * scanlineLength + (col - 1) * pixelBytes + (i % pixelBytes)]; | |
} | |
p = left + upper - upperLeft; | |
pa = Math.abs(p - left); | |
pb = Math.abs(p - upper); | |
pc = Math.abs(p - upperLeft); | |
if (pa <= pb && pa <= pc) { | |
paeth = left; | |
} else if (pb <= pc) { | |
paeth = upper; | |
} else { | |
paeth = upperLeft; | |
} | |
pixels[c++] = (_byte + paeth) % 256; | |
} | |
break; | |
default: | |
throw new Error("Invalid filter algorithm: " + data[pos - 1]); | |
} | |
row++; | |
} | |
return pixels; | |
}; | |
PNG.prototype.decodePalette = function() { | |
var c, i, length, palette, pos, ret, transparency, _ref, _ref2; | |
palette = this.palette; | |
transparency = this.transparency.indexed || []; | |
ret = new Uint8Array((transparency.length || 0) + palette.length); | |
pos = 0; | |
length = palette.length; | |
c = 0; | |
for (i = 0, _ref = palette.length; i < _ref; i += 3) { | |
ret[pos++] = palette[i]; | |
ret[pos++] = palette[i + 1]; | |
ret[pos++] = palette[i + 2]; | |
ret[pos++] = (_ref2 = transparency[c++]) != null ? _ref2 : 255; | |
} | |
return ret; | |
}; | |
PNG.prototype.copyToImageData = function(imageData, pixels) { | |
var alpha, colors, data, i, input, j, k, length, palette, v, _ref; | |
colors = this.colors; | |
palette = null; | |
alpha = this.hasAlphaChannel; | |
if (this.palette.length) { | |
palette = (_ref = this._decodedPalette) != null ? _ref : this._decodedPalette = this.decodePalette(); | |
colors = 4; | |
alpha = true; | |
} | |
data = imageData.data; | |
length = data.length; | |
input = palette || pixels; | |
i = j = 0; | |
if (colors === 1) { | |
while (i < length) { | |
k = palette ? pixels[i / 4] * 4 : j; | |
v = input[k++]; | |
data[i++] = v; | |
data[i++] = v; | |
data[i++] = v; | |
data[i++] = alpha ? input[k++] : 255; | |
j = k; | |
} | |
} else { | |
while (i < length) { | |
k = palette ? pixels[i / 4] * 4 : j; | |
data[i++] = input[k++]; | |
data[i++] = input[k++]; | |
data[i++] = input[k++]; | |
data[i++] = alpha ? input[k++] : 255; | |
j = k; | |
} | |
} | |
}; | |
PNG.prototype.decode = function() { | |
var ret; | |
ret = new Uint8Array(this.width * this.height * 4); | |
this.copyToImageData(ret, this.decodePixels()); | |
return ret; | |
}; | |
scratchCanvas = document.createElement('canvas'); | |
scratchCtx = scratchCanvas.getContext('2d'); | |
makeImage = function(imageData) { | |
var img; | |
scratchCtx.width = imageData.width; | |
scratchCtx.height = imageData.height; | |
scratchCtx.clearRect(0, 0, imageData.width, imageData.height); | |
scratchCtx.putImageData(imageData, 0, 0); | |
img = new Image; | |
img.src = scratchCanvas.toDataURL(); | |
return img; | |
}; | |
PNG.prototype.decodeFrames = function(ctx) { | |
var frame, i, imageData, pixels, _len, _ref, _results; | |
if (!this.animation) return; | |
_ref = this.animation.frames; | |
_results = []; | |
for (i = 0, _len = _ref.length; i < _len; i++) { | |
frame = _ref[i]; | |
imageData = ctx.createImageData(frame.width, frame.height); | |
pixels = this.decodePixels(new Uint8Array(frame.data)); | |
this.copyToImageData(imageData, pixels); | |
frame.imageData = imageData; | |
_results.push(frame.image = makeImage(imageData)); | |
} | |
return _results; | |
}; | |
PNG.prototype.renderFrame = function(ctx, number) { | |
var frame, frames, prev; | |
frames = this.animation.frames; | |
frame = frames[number]; | |
prev = frames[number - 1]; | |
if (number === 0) ctx.clearRect(0, 0, this.width, this.height); | |
if ((prev != null ? prev.disposeOp : void 0) === APNG_DISPOSE_OP_BACKGROUND) { | |
ctx.clearRect(prev.xOffset, prev.yOffset, prev.width, prev.height); | |
} else if ((prev != null ? prev.disposeOp : void 0) === APNG_DISPOSE_OP_PREVIOUS) { | |
ctx.putImageData(prev.imageData, prev.xOffset, prev.yOffset); | |
} | |
if (frame.blendOp === APNG_BLEND_OP_SOURCE) { | |
ctx.clearRect(frame.xOffset, frame.yOffset, frame.width, frame.height); | |
} | |
return ctx.drawImage(frame.image, frame.xOffset, frame.yOffset); | |
}; | |
PNG.prototype.animate = function(ctx) { | |
var doFrame, frameNumber, frames, numFrames, numPlays, _ref; | |
var _this = this; | |
frameNumber = 0; | |
_ref = this.animation, numFrames = _ref.numFrames, frames = _ref.frames, numPlays = _ref.numPlays; | |
return (doFrame = function() { | |
var f, frame; | |
f = frameNumber++ % numFrames; | |
frame = frames[f]; | |
_this.renderFrame(ctx, f); | |
if (numFrames > 1 && frameNumber / numFrames < numPlays) { | |
return _this.animation._timeout = setTimeout(doFrame, frame.delay); | |
} | |
})(); | |
}; | |
PNG.prototype.stopAnimation = function() { | |
var _ref; | |
return clearTimeout((_ref = this.animation) != null ? _ref._timeout : void 0); | |
}; | |
PNG.prototype.render = function(canvas) { | |
var ctx, data; | |
if (canvas._png) canvas._png.stopAnimation(); | |
canvas._png = this; | |
canvas.width = this.width; | |
canvas.height = this.height; | |
ctx = canvas.getContext("2d"); | |
if (this.animation) { | |
this.decodeFrames(ctx); | |
return this.animate(ctx); | |
} else { | |
data = ctx.createImageData(this.width, this.height); | |
this.copyToImageData(data, this.decodePixels()); | |
return ctx.putImageData(data, 0, 0); | |
} | |
}; | |
return PNG; | |
})(); | |
window.PNG = PNG; | |
}).call(this); |
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