content/canvas/test/webgl-conformance/conformance/resources/pnglib.js@925c144e1f1f
content/canvas/test/webgl-conformance/conformance/resources/pnglib.js
Fri, 16 Jan 2015 18:13:44 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Fri, 16 Jan 2015 18:13:44 +0100
- branch
- TOR_BUG_9701
- changeset 14
- 925c144e1f1f
- permissions
- -rw-r--r--
Integrate suggestion from review to improve consistency with existing code.
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 */
12 (function() {
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 }
23 function byte2(w) {
24 return String.fromCharCode((w >> 8) & 255, w & 255);
25 }
27 function byte4(w) {
28 return String.fromCharCode((w >> 24) & 255, (w >> 16) & 255, (w >> 8) & 255, w & 255);
29 }
31 function byte2lsb(w) {
32 return String.fromCharCode(w & 255, (w >> 8) & 255);
33 }
35 window.PNGlib = function(width,height,depth) {
37 this.width = width;
38 this.height = height;
39 this.depth = depth;
41 // pixel data and row filter identifier size
42 this.pix_size = height * (width + 1);
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;
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
60 this.buffer = new Array();
61 this.palette = new Object();
62 this.pindex = 0;
64 var _crc32 = new Array();
66 // initialize buffer with zero bytes
67 for (var i = 0; i < this.buffer_size; i++) {
68 this.buffer[i] = "\x00";
69 }
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');
78 // initialize deflate header
79 var header = ((8 + (7 << 4)) << 8) | (3 << 6);
80 header+= 31 - (header % 31);
82 write(this.buffer, this.idat_offs + 8, byte2(header));
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 }
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 }
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 }
117 // convert a color and build up the palette
118 this.color = function(red, green, blue, alpha) {
120 alpha = alpha >= 0 ? alpha : 255;
121 var color = (((((alpha << 8) | red) << 8) | green) << 8) | blue;
123 if (typeof this.palette[color] == "undefined") {
124 if (this.pindex == this.depth) return "\x00";
126 var ndx = this.plte_offs + 8 + 3 * this.pindex;
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);
133 this.palette[color] = String.fromCharCode(this.pindex++);
134 }
135 return this.palette[color];
136 }
138 // output a PNG string, Base64 encoded
139 this.getBase64 = function() {
141 var s = this.getDump();
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 = "";
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 }
162 // output a PNG string
163 this.getDump = function() {
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;
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));
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 }
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);
202 // convert PNG to string
203 return "\211PNG\r\n\032\n"+this.buffer.join('');
204 }
205 }
207 })();
