AS3、Flex图像解码器（JPG格式）

主要用在把图片信息（客户端通常是BitmapData）编码成JPG格式的二进制流，以便传输。

直接把复制下面的代码创建新类即可用。

import flash.geom.*;
import flash.display.*;
import flash.utils.*;

/**
* Class that converts BitmapData into a valid JPEG
*/
public class JPGEncoder
{

// Static table initialization

private var ZigZag:Array = [
0, 1, 5, 6,14,15,27,28,
2, 4, 7,13,16,26,29,42,
3, 8,12,17,25,30,41,43,
9,11,18,24,31,40,44,53,
10,19,23,32,39,45,52,54,
20,22,33,38,46,51,55,60,
21,34,37,47,50,56,59,61,
35,36,48,49,57,58,62,63
];

private var YTable:Array = new Array(64);
private var UVTable:Array = new Array(64);
private var fdtbl_Y:Array = new Array(64);
private var fdtbl_UV:Array = new Array(64);

private function initQuantTables(sf:int):void
{
var i:int;
var t:Number;
var YQT:Array = [
16, 11, 10, 16, 24, 40, 51, 61,
12, 12, 14, 19, 26, 58, 60, 55,
14, 13, 16, 24, 40, 57, 69, 56,
14, 17, 22, 29, 51, 87, 80, 62,
18, 22, 37, 56, 68,109,103, 77,
24, 35, 55, 64, 81,104,113, 92,
49, 64, 78, 87,103,121,120,101,
72, 92, 95, 98,112,100,103, 99
];
for (i = 0; i < 64; i++) {
t = Math.floor((YQT[i]*sf+50)/100);
if (t < 1) {
t = 1;
} else if (t > 255) {
t = 255;
}
YTable[ZigZag[i]] = t;
}
var UVQT:Array = [
17, 18, 24, 47, 99, 99, 99, 99,
18, 21, 26, 66, 99, 99, 99, 99,
24, 26, 56, 99, 99, 99, 99, 99,
47, 66, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99
];
for (i = 0; i < 64; i++) {
t = Math.floor((UVQT[i]*sf+50)/100);
if (t < 1) {
t = 1;
} else if (t > 255) {
t = 255;
}
UVTable[ZigZag[i]] = t;
}
var aasf:Array = [
1.0, 1.387039845, 1.306562965, 1.175875602,
1.0, 0.785694958, 0.541196100, 0.275899379
];
i = 0;
for (var row:int = 0; row < 8; row++)
{
for (var col:int = 0; col < 8; col++)
{
fdtbl_Y[i] = (1.0 / (YTable [ZigZag[i]] * aasf[row] * aasf[col] * 8.0));
fdtbl_UV[i] = (1.0 / (UVTable[ZigZag[i]] * aasf[row] * aasf[col] * 8.0));
i++;
}
}
}

private var YDC_HT:Array;
private var UVDC_HT:Array;
private var YAC_HT:Array;
private var UVAC_HT:Array;

private function computeHuffmanTbl(nrcodes:Array, std_table:Array):Array
{
var codevalue:int = 0;
var pos_in_table:int = 0;
var HT:Array = new Array();
for (var k:int=1; k<=16; k++) {
for (var j:int=1; j<=nrcodes[k]; j++) {
HT[std_table[pos_in_table]] = new BitString();
HT[std_table[pos_in_table]].val = codevalue;
HT[std_table[pos_in_table]].len = k;
pos_in_table++;
codevalue++;
}
codevalue*=2;
}
return HT;
}

private var std_dc_luminance_nrcodes:Array = [0,0,1,5,1,1,1,1,1,1,0,0,0,0,0,0,0];
private var std_dc_luminance_values:Array = [0,1,2,3,4,5,6,7,8,9,10,11];
private var std_ac_luminance_nrcodes:Array = [0,0,2,1,3,3,2,4,3,5,5,4,4,0,0,1,0x7d];
private var std_ac_luminance_values:Array = [
0x01,0x02,0x03,0x00,0x04,0x11,0x05,0x12,
0x21,0x31,0x41,0x06,0x13,0x51,0x61,0x07,
0x22,0x71,0x14,0x32,0x81,0x91,0xa1,0x08,
0x23,0x42,0xb1,0xc1,0x15,0x52,0xd1,0xf0,
0x24,0x33,0x62,0x72,0x82,0x09,0x0a,0x16,
0x17,0x18,0x19,0x1a,0x25,0x26,0x27,0x28,
0x29,0x2a,0x34,0x35,0x36,0x37,0x38,0x39,
0x3a,0x43,0x44,0x45,0x46,0x47,0x48,0x49,
0x4a,0x53,0x54,0x55,0x56,0x57,0x58,0x59,
0x5a,0x63,0x64,0x65,0x66,0x67,0x68,0x69,
0x6a,0x73,0x74,0x75,0x76,0x77,0x78,0x79,
0x7a,0x83,0x84,0x85,0x86,0x87,0x88,0x89,
0x8a,0x92,0x93,0x94,0x95,0x96,0x97,0x98,
0x99,0x9a,0xa2,0xa3,0xa4,0xa5,0xa6,0xa7,
0xa8,0xa9,0xaa,0xb2,0xb3,0xb4,0xb5,0xb6,
0xb7,0xb8,0xb9,0xba,0xc2,0xc3,0xc4,0xc5,
0xc6,0xc7,0xc8,0xc9,0xca,0xd2,0xd3,0xd4,
0xd5,0xd6,0xd7,0xd8,0xd9,0xda,0xe1,0xe2,
0xe3,0xe4,0xe5,0xe6,0xe7,0xe8,0xe9,0xea,
0xf1,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,0xf8,
0xf9,0xfa
];

private var std_dc_chrominance_nrcodes:Array = [0,0,3,1,1,1,1,1,1,1,1,1,0,0,0,0,0];
private var std_dc_chrominance_values:Array = [0,1,2,3,4,5,6,7,8,9,10,11];
private var std_ac_chrominance_nrcodes:Array = [0,0,2,1,2,4,4,3,4,7,5,4,4,0,1,2,0x77];
private var std_ac_chrominance_values:Array = [
0x00,0x01,0x02,0x03,0x11,0x04,0x05,0x21,
0x31,0x06,0x12,0x41,0x51,0x07,0x61,0x71,
0x13,0x22,0x32,0x81,0x08,0x14,0x42,0x91,
0xa1,0xb1,0xc1,0x09,0x23,0x33,0x52,0xf0,
0x15,0x62,0x72,0xd1,0x0a,0x16,0x24,0x34,
0xe1,0x25,0xf1,0x17,0x18,0x19,0x1a,0x26,
0x27,0x28,0x29,0x2a,0x35,0x36,0x37,0x38,
0x39,0x3a,0x43,0x44,0x45,0x46,0x47,0x48,
0x49,0x4a,0x53,0x54,0x55,0x56,0x57,0x58,
0x59,0x5a,0x63,0x64,0x65,0x66,0x67,0x68,
0x69,0x6a,0x73,0x74,0x75,0x76,0x77,0x78,
0x79,0x7a,0x82,0x83,0x84,0x85,0x86,0x87,
0x88,0x89,0x8a,0x92,0x93,0x94,0x95,0x96,
0x97,0x98,0x99,0x9a,0xa2,0xa3,0xa4,0xa5,
0xa6,0xa7,0xa8,0xa9,0xaa,0xb2,0xb3,0xb4,
0xb5,0xb6,0xb7,0xb8,0xb9,0xba,0xc2,0xc3,
0xc4,0xc5,0xc6,0xc7,0xc8,0xc9,0xca,0xd2,
0xd3,0xd4,0xd5,0xd6,0xd7,0xd8,0xd9,0xda,
0xe2,0xe3,0xe4,0xe5,0xe6,0xe7,0xe8,0xe9,
0xea,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,0xf8,
0xf9,0xfa
];

private function initHuffmanTbl():void
{
YDC_HT = computeHuffmanTbl(std_dc_luminance_nrcodes,std_dc_luminance_values);
UVDC_HT = computeHuffmanTbl(std_dc_chrominance_nrcodes,std_dc_chrominance_values);
YAC_HT = computeHuffmanTbl(std_ac_luminance_nrcodes,std_ac_luminance_values);
UVAC_HT = computeHuffmanTbl(std_ac_chrominance_nrcodes,std_ac_chrominance_values);
}

private var bitcode:Array = new Array(65535);
private var category:Array = new Array(65535);

private function initCategoryNumber():void
{
var nrlower:int = 1;
var nrupper:int = 2;
var nr:int;
for (var cat:int=1; cat<=15; cat++) {
//Positive numbers
for (nr=nrlower; nr<nrupper; nr++) {
category[32767+nr] = cat;
bitcode[32767+nr] = new BitString();
bitcode[32767+nr].len = cat;
bitcode[32767+nr].val = nr;
}
//Negative numbers
for (nr=-(nrupper-1); nr<=-nrlower; nr++) {
category[32767+nr] = cat;
bitcode[32767+nr] = new BitString();
bitcode[32767+nr].len = cat;
bitcode[32767+nr].val = nrupper-1+nr;
}
nrlower <<= 1;
nrupper <<= 1;
}
}

// IO functions

private var byteout:ByteArray;
private var bytenew:int = 0;
private var bytepos:int = 7;

private function writeBits(bs:BitString):void
{
var value:int = bs.val;
var posval:int = bs.len-1;
while ( posval >= 0 ) {
if (value & uint(1 << posval) ) {
bytenew |= uint(1 << bytepos);
}
posval--;
bytepos--;
if (bytepos < 0) {
if (bytenew == 0xFF) {
writeByte(0xFF);
writeByte(0);
}
else {
writeByte(bytenew);
}
bytepos=7;
bytenew=0;
}
}
}

private function writeByte(value:int):void
{
byteout.writeByte(value);
}

private function writeWord(value:int):void
{
writeByte((value>>8)&0xFF);
writeByte((value )&0xFF);
}

// DCT & quantization core

private function fDCTQuant(data:Array, fdtbl:Array):Array
{
var tmp0:Number, tmp1:Number, tmp2:Number, tmp3:Number, tmp4:Number, tmp5:Number, tmp6:Number, tmp7:Number;
var tmp10:Number, tmp11:Number, tmp12:Number, tmp13:Number;
var z1:Number, z2:Number, z3:Number, z4:Number, z5:Number, z11:Number, z13:Number;
var i:int;
/* Pass 1: process rows. */
var dataOff:int=0;
for (i=0; i<8; i++) {
tmp0 = data[dataOff+0] + data[dataOff+7];
tmp7 = data[dataOff+0] - data[dataOff+7];
tmp1 = data[dataOff+1] + data[dataOff+6];
tmp6 = data[dataOff+1] - data[dataOff+6];
tmp2 = data[dataOff+2] + data[dataOff+5];
tmp5 = data[dataOff+2] - data[dataOff+5];
tmp3 = data[dataOff+3] + data[dataOff+4];
tmp4 = data[dataOff+3] - data[dataOff+4];

/* Even part */
tmp10 = tmp0 + tmp3; /* phase 2 */
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;

data[dataOff+0] = tmp10 + tmp11; /* phase 3 */
data[dataOff+4] = tmp10 - tmp11;

z1 = (tmp12 + tmp13) * 0.707106781; /* c4 */
data[dataOff+2] = tmp13 + z1; /* phase 5 */
data[dataOff+6] = tmp13 - z1;

/* Odd part */
tmp10 = tmp4 + tmp5; /* phase 2 */
tmp11 = tmp5 + tmp6;
tmp12 = tmp6 + tmp7;

/* The rotator is modified from fig 4-8 to avoid extra negations. */
z5 = (tmp10 - tmp12) * 0.382683433; /* c6 */
z2 = 0.541196100 * tmp10 + z5; /* c2-c6 */
z4 = 1.306562965 * tmp12 + z5; /* c2+c6 */
z3 = tmp11 * 0.707106781; /* c4 */

z11 = tmp7 + z3; /* phase 5 */
z13 = tmp7 - z3;

data[dataOff+5] = z13 + z2; /* phase 6 */
data[dataOff+3] = z13 - z2;
data[dataOff+1] = z11 + z4;
data[dataOff+7] = z11 - z4;

dataOff += 8; /* advance pointer to next row */
}

/* Pass 2: process columns. */
dataOff = 0;
for (i=0; i<8; i++) {
tmp0 = data[dataOff+ 0] + data[dataOff+56];
tmp7 = data[dataOff+ 0] - data[dataOff+56];
tmp1 = data[dataOff+ 8] + data[dataOff+48];
tmp6 = data[dataOff+ 8] - data[dataOff+48];
tmp2 = data[dataOff+16] + data[dataOff+40];
tmp5 = data[dataOff+16] - data[dataOff+40];
tmp3 = data[dataOff+24] + data[dataOff+32];
tmp4 = data[dataOff+24] - data[dataOff+32];

/* Even part */
tmp10 = tmp0 + tmp3; /* phase 2 */
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;

data[dataOff+ 0] = tmp10 + tmp11; /* phase 3 */
data[dataOff+32] = tmp10 - tmp11;

z1 = (tmp12 + tmp13) * 0.707106781; /* c4 */
data[dataOff+16] = tmp13 + z1; /* phase 5 */
data[dataOff+48] = tmp13 - z1;

/* Odd part */
tmp10 = tmp4 + tmp5; /* phase 2 */
tmp11 = tmp5 + tmp6;
tmp12 = tmp6 + tmp7;

/* The rotator is modified from fig 4-8 to avoid extra negations. */
z5 = (tmp10 - tmp12) * 0.382683433; /* c6 */
z2 = 0.541196100 * tmp10 + z5; /* c2-c6 */
z4 = 1.306562965 * tmp12 + z5; /* c2+c6 */
z3 = tmp11 * 0.707106781; /* c4 */

z11 = tmp7 + z3; /* phase 5 */
z13 = tmp7 - z3;

data[dataOff+40] = z13 + z2; /* phase 6 */
data[dataOff+24] = z13 - z2;
data[dataOff+ 8] = z11 + z4;
data[dataOff+56] = z11 - z4;

dataOff++; /* advance pointer to next column */
}

// Quantize/descale the coefficients
for (i=0; i<64; i++) {
// Apply the quantization and scaling factor & Round to nearest integer
data[i] = Math.round((data[i]*fdtbl[i]));
}
return data;
}

// Chunk writing

private function writeAPP0():void
{
writeWord(0xFFE0); // marker
writeWord(16); // length
writeByte(0x4A); // J
writeByte(0x46); // F
writeByte(0x49); // I
writeByte(0x46); // F
writeByte(0); // = "JFIF",'\0'
writeByte(1); // versionhi
writeByte(1); // versionlo
writeByte(0); // xyunits
writeWord(1); // xdensity
writeWord(1); // ydensity
writeByte(0); // thumbnwidth
writeByte(0); // thumbnheight
}

private function writeSOF0(width:int, height:int):void
{
writeWord(0xFFC0); // marker
writeWord(17); // length, truecolor YUV JPG
writeByte(8); // precision
writeWord(height);
writeWord(width);
writeByte(3); // nrofcomponents
writeByte(1); // IdY
writeByte(0x11); // HVY
writeByte(0); // QTY
writeByte(2); // IdU
writeByte(0x11); // HVU
writeByte(1); // QTU
writeByte(3); // IdV
writeByte(0x11); // HVV
writeByte(1); // QTV
}

private function writeDQT():void
{
writeWord(0xFFDB); // marker
writeWord(132); // length
writeByte(0);
var i:int;
for (i=0; i<64; i++) {
writeByte(YTable[i]);
}
writeByte(1);
for (i=0; i<64; i++) {
writeByte(UVTable[i]);
}
}

private function writeDHT():void
{
writeWord(0xFFC4); // marker
writeWord(0x01A2); // length
var i:int;

writeByte(0); // HTYDCinfo
for (i=0; i<16; i++) {
writeByte(std_dc_luminance_nrcodes[i+1]);
}
for (i=0; i<=11; i++) {
writeByte(std_dc_luminance_values[i]);
}

writeByte(0x10); // HTYACinfo
for (i=0; i<16; i++) {
writeByte(std_ac_luminance_nrcodes[i+1]);
}
for (i=0; i<=161; i++) {
writeByte(std_ac_luminance_values[i]);
}

writeByte(1); // HTUDCinfo
for (i=0; i<16; i++) {
writeByte(std_dc_chrominance_nrcodes[i+1]);
}
for (i=0; i<=11; i++) {
writeByte(std_dc_chrominance_values[i]);
}

writeByte(0x11); // HTUACinfo
for (i=0; i<16; i++) {
writeByte(std_ac_chrominance_nrcodes[i+1]);
}
for (i=0; i<=161; i++) {
writeByte(std_ac_chrominance_values[i]);
}
}

private function writeSOS():void
{
writeWord(0xFFDA); // marker
writeWord(12); // length
writeByte(3); // nrofcomponents
writeByte(1); // IdY
writeByte(0); // HTY
writeByte(2); // IdU
writeByte(0x11); // HTU
writeByte(3); // IdV
writeByte(0x11); // HTV
writeByte(0); // Ss
writeByte(0x3f); // Se
writeByte(0); // Bf
}

// Core processing
private var DU:Array = new Array(64);

private function processDU(CDU:Array, fdtbl:Array, DC:Number, HTDC:Array, HTAC:Array):Number
{
var EOB:BitString = HTAC[0x00];
var M16zeroes:BitString = HTAC[0xF0];
var i:int;

var DU_DCT:Array = fDCTQuant(CDU, fdtbl);
//ZigZag reorder
for (i=0;i<64;i++) {
DU[ZigZag[i]]=DU_DCT[i];
}
var Diff:int = DU[0] - DC; DC = DU[0];
//Encode DC
if (Diff==0) {
writeBits(HTDC[0]); // Diff might be 0
} else {
writeBits(HTDC[category[32767+Diff]]);
writeBits(bitcode[32767+Diff]);
}
//Encode ACs
var end0pos:int = 63;
for (; (end0pos>0)&&(DU[end0pos]==0); end0pos--) {
};
//end0pos = first element in reverse order !=0
if ( end0pos == 0) {
writeBits(EOB);
return DC;
}
i = 1;
while ( i <= end0pos ) {
var startpos:int = i;
for (; (DU[i]==0) && (i<=end0pos); i++) {
}
var nrzeroes:int = i-startpos;
if ( nrzeroes >= 16 ) {
for (var nrmarker:int=1; nrmarker <= nrzeroes/16; nrmarker++) {
writeBits(M16zeroes);
}
nrzeroes = int(nrzeroes&0xF);
}
writeBits(HTAC[nrzeroes*16+category[32767+DU[i]]]);
writeBits(bitcode[32767+DU[i]]);
i++;
}
if ( end0pos != 63 ) {
writeBits(EOB);
}
return DC;
}

private var YDU:Array = new Array(64);
private var UDU:Array = new Array(64);
private var VDU:Array = new Array(64);

private function RGB2YUV(img:BitmapData, xpos:int, ypos:int):void
{
var pos:int=0;
for (var y:int=0; y<8; y++) {
for (var x:int=0; x<8; x++) {
var P:uint = img.getPixel32(xpos+x,ypos+y);
var R:Number = Number((P>>16)&0xFF);
var G:Number = Number((P>> 8)&0xFF);
var B:Number = Number((P )&0xFF);
YDU[pos]=((( 0.29900)*R+( 0.58700)*G+( 0.11400)*B))-128;
UDU[pos]=(((-0.16874)*R+(-0.33126)*G+( 0.50000)*B));
VDU[pos]=((( 0.50000)*R+(-0.41869)*G+(-0.08131)*B));
pos++;
}
}
}

/**
* Constructor for JPEGEncoder class
*
* @param quality The quality level between 1 and 100 that detrmines the
* level of compression used in the generated JPEG
* @langversion ActionScript 3.0
* @playerversion Flash 9.0
* @tiptext
*/
public function JPGEncoder(quality:Number = 50)
{
if (quality <= 0) {
quality = 1;
}
if (quality > 100) {
quality = 100;
}
var sf:int = 0;
if (quality < 50) {
sf = int(5000 / quality);
} else {
sf = int(200 - quality*2);
}
// Create tables
initHuffmanTbl();
initCategoryNumber();
initQuantTables(sf);
}

/**
* Created a JPEG image from the specified BitmapData
*
* @param image The BitmapData that will be converted into the JPEG format.
* @return a ByteArray representing the JPEG encoded image data.
* @langversion ActionScript 3.0
* @playerversion Flash 9.0
* @tiptext
*/
public function encode(image:BitmapData):ByteArray
{
// Initialize bit writer
byteout = new ByteArray();
bytenew=0;
bytepos=7;

// Add JPEG headers
writeWord(0xFFD8); // SOI
writeAPP0();
writeDQT();
writeSOF0(image.width,image.height);
writeDHT();
writeSOS();


// Encode 8x8 macroblocks
var DCY:Number=0;
var DCU:Number=0;
var DCV:Number=0;
bytenew=0;
bytepos=7;
for (var ypos:int=0; ypos<image.height; ypos+=8) {
for (var xpos:int=0; xpos<image.width; xpos+=8) {
RGB2YUV(image, xpos, ypos);
DCY = processDU(YDU, fdtbl_Y, DCY, YDC_HT, YAC_HT);
DCU = processDU(UDU, fdtbl_UV, DCU, UVDC_HT, UVAC_HT);
DCV = processDU(VDU, fdtbl_UV, DCV, UVDC_HT, UVAC_HT);
}
}

// Do the bit alignment of the EOI marker
if ( bytepos >= 0 ) {
var fillbits:BitString = new BitString();
fillbits.len = bytepos+1;
fillbits.val = (1<<(bytepos+1))-1;
writeBits(fillbits);
}

writeWord(0xFFD9); //EOI
return byteout;
}
}

 

 使用方式：

var jpg:JPGEncoder=new JPGEncoder;

var byteArray:ByteArray=jpg.encode(getBitmapData(lImage));