path: root/contexts/data/lib/closure-library/third_party/closure/goog/jpeg_encoder/jpeg_encoder_basic.js

/**
 * @license
  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.
*/
/**
 * @license
JPEG encoder ported to JavaScript and optimized by Andreas Ritter, www.bytestrom.eu, 11/2009

Basic GUI blocking jpeg encoder

v 0.9
*/

/**
 * @fileoverview This code was ported from
 * http://www.bytestrom.eu/blog/2009/1120a_jpeg_encoder_for_javascript and
 * modified slightly for Closure.
 */

goog.provide('goog.crypt.JpegEncoder');

goog.require('goog.crypt.base64');

/**
 * Initializes the JpegEncoder.
 *
 * @constructor
 * @param {number=} opt_quality The compression quality. Default 50.
 */
goog.crypt.JpegEncoder = function(opt_quality) {
  var self = this;
  var fround = Math.round;
  var ffloor = Math.floor;
  var YTable = new Array(64);
  var UVTable = new Array(64);
  var fdtbl_Y = new Array(64);
  var fdtbl_UV = new Array(64);
  var YDC_HT;
  var UVDC_HT;
  var YAC_HT;
  var UVAC_HT;

  var bitcode = new Array(65535);
  var category = new Array(65535);
  var outputfDCTQuant = new Array(64);
  var DU = new Array(64);
  var byteout = [];
  var bytenew = 0;
  var bytepos = 7;

  var YDU = new Array(64);
  var UDU = new Array(64);
  var VDU = new Array(64);
  var clt = new Array(256);
  var RGB_YUV_TABLE = new Array(2048);
  var currentQuality;

  var ZigZag = [
       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
    ];

  var std_dc_luminance_nrcodes = [0,0,1,5,1,1,1,1,1,1,0,0,0,0,0,0,0];
  var std_dc_luminance_values = [0,1,2,3,4,5,6,7,8,9,10,11];
  var std_ac_luminance_nrcodes = [0,0,2,1,3,3,2,4,3,5,5,4,4,0,0,1,0x7d];
  var std_ac_luminance_values = [
      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
    ];

  var std_dc_chrominance_nrcodes = [0,0,3,1,1,1,1,1,1,1,1,1,0,0,0,0,0];
  var std_dc_chrominance_values = [0,1,2,3,4,5,6,7,8,9,10,11];
  var std_ac_chrominance_nrcodes = [0,0,2,1,2,4,4,3,4,7,5,4,4,0,1,2,0x77];
  var std_ac_chrominance_values = [
      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
    ];

  function initQuantTables(sf){
      var YQT = [
        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 (var i = 0; i < 64; i++) {
        var t = ffloor((YQT[i]*sf+50)/100);
        if (t < 1) {
          t = 1;
        } else if (t > 255) {
          t = 255;
        }
        YTable[ZigZag[i]] = t;
      }
      var UVQT = [
        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 (var j = 0; j < 64; j++) {
        var u = ffloor((UVQT[j]*sf+50)/100);
        if (u < 1) {
          u = 1;
        } else if (u > 255) {
          u = 255;
        }
        UVTable[ZigZag[j]] = u;
      }
      var aasf = [
        1.0, 1.387039845, 1.306562965, 1.175875602,
        1.0, 0.785694958, 0.541196100, 0.275899379
      ];
      var k = 0;
      for (var row = 0; row < 8; row++)
      {
        for (var col = 0; col < 8; col++)
        {
          fdtbl_Y[k]  = (1.0 / (YTable [ZigZag[k]] * aasf[row] * aasf[col] * 8.0));
          fdtbl_UV[k] = (1.0 / (UVTable[ZigZag[k]] * aasf[row] * aasf[col] * 8.0));
          k++;
        }
      }
    }

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

    function initHuffmanTbl()
    {
      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);
    }

    function initCategoryNumber()
    {
      var nrlower = 1;
      var nrupper = 2;
      for (var cat = 1; cat <= 15; cat++) {
        //Positive numbers
        for (var nr = nrlower; nr<nrupper; nr++) {
          category[32767+nr] = cat;
          bitcode[32767+nr] = [];
          bitcode[32767+nr][1] = cat;
          bitcode[32767+nr][0] = nr;
        }
        //Negative numbers
        for (var nrneg =-(nrupper-1); nrneg<=-nrlower; nrneg++) {
          category[32767+nrneg] = cat;
          bitcode[32767+nrneg] = [];
          bitcode[32767+nrneg][1] = cat;
          bitcode[32767+nrneg][0] = nrupper-1+nrneg;
        }
        nrlower <<= 1;
        nrupper <<= 1;
      }
    }

    function initRGBYUVTable() {
      for(var i = 0; i < 256;i++) {
        RGB_YUV_TABLE[i]          =  19595 * i;
        RGB_YUV_TABLE[(i+ 256)>>0]   =  38470 * i;
        RGB_YUV_TABLE[(i+ 512)>>0]   =   7471 * i + 0x8000;
        RGB_YUV_TABLE[(i+ 768)>>0]   = -11059 * i;
        RGB_YUV_TABLE[(i+1024)>>0]   = -21709 * i;
        RGB_YUV_TABLE[(i+1280)>>0]   =  32768 * i + 0x807FFF;
        RGB_YUV_TABLE[(i+1536)>>0]   = -27439 * i;
        RGB_YUV_TABLE[(i+1792)>>0]   = - 5329 * i;
      }
    }

    // IO functions
    function writeBits(bs)
    {
      var value = bs[0];
      var posval = bs[1]-1;
      while ( posval >= 0 ) {
        if (value & (1 << posval) ) {
          bytenew |= (1 << bytepos);
        }
        posval--;
        bytepos--;
        if (bytepos < 0) {
          if (bytenew == 0xFF) {
            writeByte(0xFF);
            writeByte(0);
          }
          else {
            writeByte(bytenew);
          }
          bytepos=7;
          bytenew=0;
        }
      }
    }

    function writeByte(value)
    {
      byteout.push(clt[value]); // write char directly instead of converting later
    }

    function writeWord(value)
    {
      writeByte((value>>8)&0xFF);
      writeByte((value   )&0xFF);
    }

    // DCT & quantization core
    function fDCTQuant(data, fdtbl)
    {
      var d0, d1, d2, d3, d4, d5, d6, d7;
      /* Pass 1: process rows. */
      var dataOff=0;
      var i;
      var I8 = 8;
      var I64 = 64;
      for (i=0; i<I8; ++i)
      {
        d0 = data[dataOff];
        d1 = data[dataOff+1];
        d2 = data[dataOff+2];
        d3 = data[dataOff+3];
        d4 = data[dataOff+4];
        d5 = data[dataOff+5];
        d6 = data[dataOff+6];
        d7 = data[dataOff+7];

        var tmp0 = d0 + d7;
        var tmp7 = d0 - d7;
        var tmp1 = d1 + d6;
        var tmp6 = d1 - d6;
        var tmp2 = d2 + d5;
        var tmp5 = d2 - d5;
        var tmp3 = d3 + d4;
        var tmp4 = d3 - d4;

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

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

        var 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. */
        var z5 = (tmp10 - tmp12) * 0.382683433; /* c6 */
        var z2 = 0.541196100 * tmp10 + z5; /* c2-c6 */
        var z4 = 1.306562965 * tmp12 + z5; /* c2+c6 */
        var z3 = tmp11 * 0.707106781; /* c4 */

        var z11 = tmp7 + z3;  /* phase 5 */
        var 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<I8; ++i)
      {
        d0 = data[dataOff];
        d1 = data[dataOff + 8];
        d2 = data[dataOff + 16];
        d3 = data[dataOff + 24];
        d4 = data[dataOff + 32];
        d5 = data[dataOff + 40];
        d6 = data[dataOff + 48];
        d7 = data[dataOff + 56];

        var tmp0p2 = d0 + d7;
        var tmp7p2 = d0 - d7;
        var tmp1p2 = d1 + d6;
        var tmp6p2 = d1 - d6;
        var tmp2p2 = d2 + d5;
        var tmp5p2 = d2 - d5;
        var tmp3p2 = d3 + d4;
        var tmp4p2 = d3 - d4;

        /* Even part */
        var tmp10p2 = tmp0p2 + tmp3p2;  /* phase 2 */
        var tmp13p2 = tmp0p2 - tmp3p2;
        var tmp11p2 = tmp1p2 + tmp2p2;
        var tmp12p2 = tmp1p2 - tmp2p2;

        data[dataOff] = tmp10p2 + tmp11p2; /* phase 3 */
        data[dataOff+32] = tmp10p2 - tmp11p2;

        var z1p2 = (tmp12p2 + tmp13p2) * 0.707106781; /* c4 */
        data[dataOff+16] = tmp13p2 + z1p2; /* phase 5 */
        data[dataOff+48] = tmp13p2 - z1p2;

        /* Odd part */
        tmp10p2 = tmp4p2 + tmp5p2; /* phase 2 */
        tmp11p2 = tmp5p2 + tmp6p2;
        tmp12p2 = tmp6p2 + tmp7p2;

        /* The rotator is modified from fig 4-8 to avoid extra negations. */
        var z5p2 = (tmp10p2 - tmp12p2) * 0.382683433; /* c6 */
        var z2p2 = 0.541196100 * tmp10p2 + z5p2; /* c2-c6 */
        var z4p2 = 1.306562965 * tmp12p2 + z5p2; /* c2+c6 */
        var z3p2 = tmp11p2 * 0.707106781; /* c4 */

        var z11p2 = tmp7p2 + z3p2;  /* phase 5 */
        var z13p2 = tmp7p2 - z3p2;

        data[dataOff+40] = z13p2 + z2p2; /* phase 6 */
        data[dataOff+24] = z13p2 - z2p2;
        data[dataOff+ 8] = z11p2 + z4p2;
        data[dataOff+56] = z11p2 - z4p2;

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

      // Quantize/descale the coefficients
      var fDCTQuant;
      for (i=0; i<I64; ++i)
      {
        // Apply the quantization and scaling factor & Round to nearest integer
        fDCTQuant = data[i]*fdtbl[i];
        outputfDCTQuant[i] = (fDCTQuant > 0.0) ? ((fDCTQuant + 0.5)|0) : ((fDCTQuant - 0.5)|0);
        //outputfDCTQuant[i] = fround(fDCTQuant);

      }
      return outputfDCTQuant;
    }

    function writeAPP0()
    {
      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
    }

    function writeSOF0(width, height)
    {
      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
    }

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

    function writeDHT()
    {
      writeWord(0xFFC4); // marker
      writeWord(0x01A2); // length

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

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

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

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

    function writeSOS()
    {
      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
    }

    function processDU(CDU, fdtbl, DC, HTDC, HTAC){
      var EOB = HTAC[0x00];
      var M16zeroes = HTAC[0xF0];
      var pos;
      var I16 = 16;
      var I63 = 63;
      var I64 = 64;
      var DU_DCT = fDCTQuant(CDU, fdtbl);
      //ZigZag reorder
      for (var j=0;j<I64;++j) {
        DU[ZigZag[j]]=DU_DCT[j];
      }
      var Diff = DU[0] - DC; DC = DU[0];
      //Encode DC
      if (Diff==0) {
        writeBits(HTDC[0]); // Diff might be 0
      } else {
        pos = 32767+Diff;
        writeBits(HTDC[category[pos]]);
        writeBits(bitcode[pos]);
      }
      //Encode ACs
      var end0pos = 63; // was const... which is crazy
      for (; (end0pos>0)&&(DU[end0pos]==0); end0pos--) {};
      //end0pos = first element in reverse order !=0
      if ( end0pos == 0) {
        writeBits(EOB);
        return DC;
      }
      var i = 1;
      var lng;
      while ( i <= end0pos ) {
        var startpos = i;
        for (; (DU[i]==0) && (i<=end0pos); ++i) {}
        var nrzeroes = i-startpos;
        if ( nrzeroes >= I16 ) {
          lng = nrzeroes>>4;
          for (var nrmarker=1; nrmarker <= lng; ++nrmarker)
            writeBits(M16zeroes);
          nrzeroes = nrzeroes&0xF;
        }
        pos = 32767+DU[i];
        writeBits(HTAC[(nrzeroes<<4)+category[pos]]);
        writeBits(bitcode[pos]);
        i++;
      }
      if ( end0pos != I63 ) {
        writeBits(EOB);
      }
      return DC;
    }

    function initCharLookupTable(){
      var sfcc = String.fromCharCode;
      for(var i=0; i < 256; i++){ ///// ACHTUNG // 255
        clt[i] = sfcc(i);
      }
    }

/**
 * Encodes ImageData to JPEG.
 *
 * @param {ImageData} image
 * @param {number=} opt_quality The compression quality.
 * @return {string} base64-encoded JPEG data.
 */
    this.encode = function(image,opt_quality) // image data object
    {
      if(opt_quality) setQuality(opt_quality);

      // Initialize bit writer
      byteout = new Array();
      bytenew=0;
      bytepos=7;

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


      // Encode 8x8 macroblocks
      var _DCY=0;
      var _DCU=0;
      var _DCV=0;

      bytenew=0;
      bytepos=7;


      this.encode.displayName = "_encode_";

      var imageData = image.data;
      var width = image.width;
      var height = image.height;

      var quadWidth = width*4;
      var tripleWidth = width*3;

      var x, y = 0;
      var r, g, b;
      var start,p, col,row,pos;
      while(y < height){
        x = 0;
        while(x < quadWidth){
        start = quadWidth * y + x;
        p = start;
        col = -1;
        row = 0;

        for(pos=0; pos < 64; pos++){
          row = pos >> 3;// /8
          col = ( pos & 7 ) * 4; // %8
          p = start + ( row * quadWidth ) + col;

          if(y+row >= height){ // padding bottom
            p-= (quadWidth*(y+1+row-height));
          }

          if(x+col >= quadWidth){ // padding right
            p-= ((x+col) - quadWidth +4)
          }

          r = imageData[ p++ ];
          g = imageData[ p++ ];
          b = imageData[ p++ ];


          /* // calculate YUV values dynamically
          YDU[pos]=((( 0.29900)*r+( 0.58700)*g+( 0.11400)*b))-128; //-0x80
          UDU[pos]=(((-0.16874)*r+(-0.33126)*g+( 0.50000)*b));
          VDU[pos]=((( 0.50000)*r+(-0.41869)*g+(-0.08131)*b));
          */

          // use lookup table (slightly faster)
          YDU[pos] = ((RGB_YUV_TABLE[r]             + RGB_YUV_TABLE[(g +  256)>>0] + RGB_YUV_TABLE[(b +  512)>>0]) >> 16)-128;
          UDU[pos] = ((RGB_YUV_TABLE[(r +  768)>>0] + RGB_YUV_TABLE[(g + 1024)>>0] + RGB_YUV_TABLE[(b + 1280)>>0]) >> 16)-128;
          VDU[pos] = ((RGB_YUV_TABLE[(r + 1280)>>0] + RGB_YUV_TABLE[(g + 1536)>>0] + RGB_YUV_TABLE[(b + 1792)>>0]) >> 16)-128;

        }

        _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);
        x+=32;
        }
        y+=8;
      }


      ////////////////////////////////////////////////////////////////

      // Do the bit alignment of the EOI marker
      if ( bytepos >= 0 ) {
        var fillbits = [];
        fillbits[1] = bytepos+1;
        fillbits[0] = (1<<(bytepos+1))-1;
        writeBits(fillbits);
      }

      writeWord(0xFFD9); //EOI

      var jpegDataUri = 'data:image/jpeg;base64,'
        + goog.crypt.base64.encodeString(byteout.join(''));

      byteout = [];

      return jpegDataUri
  }

  function setQuality(quality){
    if (quality <= 0) {
      quality = 1;
    }
    if (quality > 100) {
      quality = 100;
    }

    if(currentQuality == quality) return // don't recalc if unchanged

    var sf = 0;
    if (quality < 50) {
      sf = Math.floor(5000 / quality);
    } else {
      sf = Math.floor(200 - quality*2);
    }

    initQuantTables(sf);
    currentQuality = quality;
  }

  function init(){
    if(!opt_quality) opt_quality = 50;
    // Create tables
    initCharLookupTable()
    initHuffmanTbl();
    initCategoryNumber();
    initRGBYUVTable();

    setQuality(opt_quality);
  }

  init();

};