JPGEncoder

package com.adobe.images
{
 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;
  }
 }
}