/**
* PNG encoding class from kaourantin.net, optimised by 5etdemi.com/blog
* @author kaourantin
* @version 0.1
*/
package org.alivepdf.encoding
{
import flash.display.BitmapData;
import flash.geom.Rectangle;
import flash.utils.ByteArray;
public final class PNGEncoder {
public static function encode(img:BitmapData, type:uint = 0):ByteArray
{
var png:ByteArray = new ByteArray();
png.writeUnsignedInt(0x89504e47);
png.writeUnsignedInt(0x0D0A1A0A);
var IHDR:ByteArray = new ByteArray();
IHDR.writeInt(img.width);
IHDR.writeInt(img.height);
if(img.transparent || type == 0)
{
IHDR.writeUnsignedInt(0x08060000); }
else
{
IHDR.writeUnsignedInt(0x08020000); }
IHDR.writeByte(0);
writeChunk(png,0x49484452,IHDR);
var IDAT:ByteArray= new ByteArray();
switch(type)
{
case 0:
writeRaw(img, IDAT);
break;
case 1:
writeSub(img, IDAT);
break;
}
IDAT.compress();
writeChunk(png,0x49444154,IDAT);
writeChunk(png,0x49454E44,null);
return png;
}
private static function writeRaw(img:BitmapData, IDAT:ByteArray):void
{
var h:int = img.height;
var w:int = img.width;
var transparent:Boolean = img.transparent;
var subImage:ByteArray;
for(var i:int=0;i < h;i++) {
if ( !transparent ) {
subImage = img.getPixels(
new Rectangle(0, i, w, 1));
subImage[0] = 0;
IDAT.writeBytes(subImage);
IDAT.writeByte(0xff);
} else {
IDAT.writeByte(0);
var p:uint;
for(var j:int=0;j < w;j++) {
p = img.getPixel32(j,i);
IDAT.writeUnsignedInt(
uint(((p&0xFFFFFF) << 8)|
(p>>>24)));
}
}
}
}
private static function writeSub(img:BitmapData, IDAT:ByteArray):void
{
var r1:uint;
var g1:uint;
var b1:uint;
var a1:uint;
var r2:uint;
var g2:uint;
var b2:uint;
var a2:uint;
var r3:uint;
var g3:uint;
var b3:uint;
var a3:uint;
var p:uint;
var h:int = img.height;
var w:int = img.width;
for(var i:int=0;i < h;i++) {
IDAT.writeByte(1);
if ( !img.transparent ) {
r1 = 0;
g1 = 0;
b1 = 0;
a1 = 0xff;
for(var j:int=0;j < w;j++) {
p = img.getPixel(j,i);
r2 = p >> 16 & 0xff;
g2 = p >> 8 & 0xff;
b2 = p & 0xff;
r3 = (r2 - r1 + 256) & 0xff;
g3 = (g2 - g1 + 256) & 0xff;
b3 = (b2 - b1 + 256) & 0xff;
IDAT.writeByte(r3);
IDAT.writeByte(g3);
IDAT.writeByte(b3);
r1 = r2;
g1 = g2;
b1 = b2;
a1 = 0;
}
} else {
r1 = 0;
g1 = 0;
b1 = 0;
a1 = 0;
for(var k:int=0;k < w;k++) {
p = img.getPixel32(k,i);
a2 = p >> 24 & 0xff;
r2 = p >> 16 & 0xff;
g2 = p >> 8 & 0xff;
b2 = p & 0xff;
r3 = (r2 - r1 + 256) & 0xff;
g3 = (g2 - g1 + 256) & 0xff;
b3 = (b2 - b1 + 256) & 0xff;
a3 = (a2 - a1 + 256) & 0xff;
IDAT.writeByte(r3);
IDAT.writeByte(g3);
IDAT.writeByte(b3);
IDAT.writeByte(a3);
r1 = r2;
g1 = g2;
b1 = b2;
a1 = a2;
}
}
}
}
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 = [];
for (var n:uint = 0; n < 256; n++) {
var c:uint = n;
for (var k:uint = 0; k < 8; k++) {
if (n & 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()) &
0xff] ^ (c >>> 8));
}
c = uint(c^uint(0xffffffff));
png.position = e;
png.writeUnsignedInt(c);
}
}
}