third_party/WebKit/LayoutTests/fast/canvas/webgl/resources/pnglib.js

   1 /**
   2 * A handy class to calculate color values.
   3 *
   4 * @version 1.0
   5 * @author Robert Eisele <robert@xarg.org>
   6 * @copyright Copyright (c) 2010, Robert Eisele
   7 * @link http://www.xarg.org/2010/03/generate-client-side-png-files-using-javascript/
   8 * @license http://www.opensource.org/licenses/bsd-license.php BSD License
   9 *
  10 */
  11
  12 (function() {
  13
  14     // helper functions for that ctx
  15     function write(buffer, offs) {
  16         for (var i = 2; i < arguments.length; i++) {
  17             for (var j = 0; j < arguments[i].length; j++) {
  18                 buffer[offs++] = arguments[i].charAt(j);
  19             }
  20         }
  21     }
  22
  23     function byte2(w) {
  24         return String.fromCharCode((w >> 8) & 255, w & 255);
  25     }
  26
  27     function byte4(w) {
  28         return String.fromCharCode((w >> 24) & 255, (w >> 16) & 255, (w >> 8) & 255, w & 255);
  29     }
  30
  31     function byte2lsb(w) {
  32         return String.fromCharCode(w & 255, (w >> 8) & 255);
  33     }
  34
  35     window.PNGlib = function(width,height,depth) {
  36
  37         this.width   = width;
  38         this.height  = height;
  39         this.depth   = depth;
  40
  41         // pixel data and row filter identifier size
  42         this.pix_size = height * (width + 1);
  43
  44         // deflate header, pix_size, block headers, adler32 checksum
  45         this.data_size = 2 + this.pix_size + 5 * Math.floor((0xfffe + this.pix_size) / 0xffff) + 4;
  46
  47         // offsets and sizes of Png chunks
  48         this.ihdr_offs = 0;                                    // IHDR offset and size
  49         this.ihdr_size = 4 + 4 + 13 + 4;
  50         this.plte_offs = this.ihdr_offs + this.ihdr_size;    // PLTE offset and size
  51         this.plte_size = 4 + 4 + 3 * depth + 4;
  52         this.trns_offs = this.plte_offs + this.plte_size;    // tRNS offset and size
  53         this.trns_size = 4 + 4 + depth + 4;
  54         this.idat_offs = this.trns_offs + this.trns_size;    // IDAT offset and size
  55         this.idat_size = 4 + 4 + this.data_size + 4;
  56         this.iend_offs = this.idat_offs + this.idat_size;    // IEND offset and size
  57         this.iend_size = 4 + 4 + 4;
  58         this.buffer_size  = this.iend_offs + this.iend_size;    // total PNG size
  59
  60         this.buffer  = new Array();
  61         this.palette = new Object();
  62         this.pindex  = 0;
  63
  64         var _crc32 = new Array();
  65
  66         // initialize buffer with zero bytes
  67         for (var i = 0; i < this.buffer_size; i++) {
  68             this.buffer[i] = "\x00";
  69         }
  70
  71         // initialize non-zero elements
  72         write(this.buffer, this.ihdr_offs, byte4(this.ihdr_size - 12), 'IHDR', byte4(width), byte4(height), "\x08\x03");
  73         write(this.buffer, this.plte_offs, byte4(this.plte_size - 12), 'PLTE');
  74         write(this.buffer, this.trns_offs, byte4(this.trns_size - 12), 'tRNS');
  75         write(this.buffer, this.idat_offs, byte4(this.idat_size - 12), 'IDAT');
  76         write(this.buffer, this.iend_offs, byte4(this.iend_size - 12), 'IEND');
  77
  78         // initialize deflate header
  79         var header = ((8 + (7 << 4)) << 8) | (3 << 6);
  80         header+= 31 - (header % 31);
  81
  82         write(this.buffer, this.idat_offs + 8, byte2(header));
  83
  84         // initialize deflate block headers
  85         for (var i = 0; (i << 16) - 1 < this.pix_size; i++) {
  86             var size, bits;
  87             if (i + 0xffff < this.pix_size) {
  88                 size = 0xffff;
  89                 bits = "\x00";
  90             } else {
  91                 size = this.pix_size - (i << 16) - i;
  92                 bits = "\x01";
  93             }
  94             write(this.buffer, this.idat_offs + 8 + 2 + (i << 16) + (i << 2), bits, byte2lsb(size), byte2lsb(~size));
  95         }
  96
  97         /* Create crc32 lookup table */
  98         for (var i = 0; i < 256; i++) {
  99             var c = i;
 100             for (var j = 0; j < 8; j++) {
 101                 if (c & 1) {
 102                     c = -306674912 ^ ((c >> 1) & 0x7fffffff);
 103                 } else {
 104                     c = (c >> 1) & 0x7fffffff;
 105                 }
 106             }
 107             _crc32[i] = c;
 108         }
 109
 110         // compute the index into a png for a given pixel
 111         this.index = function(x,y) {
 112             var i = y * (this.width + 1) + x + 1;
 113             var j = this.idat_offs + 8 + 2 + 5 * Math.floor((i / 0xffff) + 1) + i;
 114             return j;
 115         }
 116
 117         // convert a color and build up the palette
 118         this.color = function(red, green, blue, alpha) {
 119
 120             alpha = alpha >= 0 ? alpha : 255;
 121             var color = (((((alpha << 8) | red) << 8) | green) << 8) | blue;
 122
 123             if (typeof this.palette[color] == "undefined") {
 124                 if (this.pindex == this.depth) return "\x00";
 125
 126                 var ndx = this.plte_offs + 8 + 3 * this.pindex;
 127
 128                 this.buffer[ndx + 0] = String.fromCharCode(red);
 129                 this.buffer[ndx + 1] = String.fromCharCode(green);
 130                 this.buffer[ndx + 2] = String.fromCharCode(blue);
 131                 this.buffer[this.trns_offs+8+this.pindex] = String.fromCharCode(alpha);
 132
 133                 this.palette[color] = String.fromCharCode(this.pindex++);
 134             }
 135             return this.palette[color];
 136         }
 137
 138         // output a PNG string, Base64 encoded
 139         this.getBase64 = function() {
 140
 141             var s = this.getDump();
 142
 143             var ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
 144             var c1, c2, c3, e1, e2, e3, e4;
 145             var l = s.length;
 146             var i = 0;
 147             var r = "";
 148
 149             do {
 150                 c1 = s.charCodeAt(i);
 151                 e1 = c1 >> 2;
 152                 c2 = s.charCodeAt(i+1);
 153                 e2 = ((c1 & 3) << 4) | (c2 >> 4);
 154                 c3 = s.charCodeAt(i+2);
 155                 if (l < i+2) { e3 = 64; } else { e3 = ((c2 & 0xf) << 2) | (c3 >> 6); }
 156                 if (l < i+3) { e4 = 64; } else { e4 = c3 & 0x3f; }
 157                 r+= ch.charAt(e1) + ch.charAt(e2) + ch.charAt(e3) + ch.charAt(e4);
 158             } while ((i+= 3) < l);
 159             return r;
 160         }
 161
 162         // output a PNG string
 163         this.getDump = function() {
 164
 165             // compute adler32 of output pixels + row filter bytes
 166             var BASE = 65521; /* largest prime smaller than 65536 */
 167             var NMAX = 5552;  /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
 168             var s1 = 1;
 169             var s2 = 0;
 170             var n = NMAX;
 171
 172             for (var y = 0; y < this.height; y++) {
 173                 for (var x = -1; x < this.width; x++) {
 174                     s1+= this.buffer[this.index(x, y)].charCodeAt(0);
 175                     s2+= s1;
 176                     if ((n-= 1) == 0) {
 177                         s1%= BASE;
 178                         s2%= BASE;
 179                         n = NMAX;
 180                     }
 181                 }
 182             }
 183             s1%= BASE;
 184             s2%= BASE;
 185             write(this.buffer, this.idat_offs + this.idat_size - 8, byte4((s2 << 16) | s1));
 186
 187             // compute crc32 of the PNG chunks
 188             function crc32(png, offs, size) {
 189                 var crc = -1;
 190                 for (var i = 4; i < size-4; i += 1) {
 191                     crc = _crc32[(crc ^ png[offs+i].charCodeAt(0)) & 0xff] ^ ((crc >> 8) & 0x00ffffff);
 192                 }
 193                 write(png, offs+size-4, byte4(crc ^ -1));
 194             }
 195
 196             crc32(this.buffer, this.ihdr_offs, this.ihdr_size);
 197             crc32(this.buffer, this.plte_offs, this.plte_size);
 198             crc32(this.buffer, this.trns_offs, this.trns_size);
 199             crc32(this.buffer, this.idat_offs, this.idat_size);
 200             crc32(this.buffer, this.iend_offs, this.iend_size);
 201
 202             // convert PNG to string
 203             return "\211PNG\r\n\032\n"+this.buffer.join('');
 204         }
 205     }
 206
 207 })();