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/*
Copyright (c) 2008, Adobe Systems Incorporated
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Adobe Systems Incorporated nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.adobe.images
{
import flash.geom.*;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.utils.ByteArray;
/**
* Class that converts BitmapData into a valid PNG
*/
public class PNGEncoder
{
/**
* Created a PNG image from the specified BitmapData
*
* @param image The BitmapData that will be converted into the PNG format.
* @return a ByteArray representing the PNG encoded image data.
* @langversion ActionScript 3.0
* @playerversion Flash 9.0
* @tiptext
*/
public static function encode(img:BitmapData):ByteArray {
// Create output byte array
var png:ByteArray = new ByteArray();
// Write PNG signature
png.writeUnsignedInt(0x89504e47);
png.writeUnsignedInt(0x0D0A1A0A);
// Build IHDR chunk
var IHDR:ByteArray = new ByteArray();
IHDR.writeInt(img.width);
IHDR.writeInt(img.height);
IHDR.writeUnsignedInt(0x08060000); // 32bit RGBA
IHDR.writeByte(0);
writeChunk(png,0x49484452,IHDR);
// Build IDAT chunk
var IDAT:ByteArray= new ByteArray();
for(var i:int=0;i < img.height;i++) {
// no filter
IDAT.writeByte(0);
var p:uint;
var j:int;
if ( !img.transparent ) {
for(j=0;j < img.width;j++) {
p = img.getPixel(j,i);
IDAT.writeUnsignedInt(
uint(((p&0xFFFFFF) << 8)|0xFF));
}
} else {
for(j=0;j < img.width;j++) {
p = img.getPixel32(j,i);
IDAT.writeUnsignedInt(
uint(((p&0xFFFFFF) << 8)|
(p>>>24)));
}
}
}
IDAT.compress();
writeChunk(png,0x49444154,IDAT);
// Build IEND chunk
writeChunk(png,0x49454E44,null);
// return PNG
return png;
}
private static var crcTable:Array;
private static var crcTableComputed:Boolean = false;
private static function writeChunk(png:ByteArray,
type:uint, data:ByteArray):void {
if (!crcTableComputed) {
crcTableComputed = true;
crcTable = [];
var c:uint;
for (var n:uint = 0; n < 256; n++) {
c = n;
for (var k:uint = 0; k < 8; k++) {
if (c & 1) {
c = uint(uint(0xedb88320) ^
uint(c >>> 1));
} else {
c = uint(c >>> 1);
}
}
crcTable[n] = c;
}
}
var len:uint = 0;
if (data != null) {
len = data.length;
}
png.writeUnsignedInt(len);
var p:uint = png.position;
png.writeUnsignedInt(type);
if ( data != null ) {
png.writeBytes(data);
}
var e:uint = png.position;
png.position = p;
c = 0xffffffff;
for (var i:int = 0; i < (e-p); i++) {
c = uint(crcTable[
(c ^ png.readUnsignedByte()) &
uint(0xff)] ^ uint(c >>> 8));
}
c = uint(c^uint(0xffffffff));
png.position = e;
png.writeUnsignedInt(c);
}
}
}
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