257 lines
6.8 KiB
JavaScript
257 lines
6.8 KiB
JavaScript
"use strict";
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/*
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Copyright (C) 2012 by Jeremy P. White <jwhite@codeweavers.com>
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This file is part of spice-html5.
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spice-html5 is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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spice-html5 is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with spice-html5. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*----------------------------------------------------------------------------
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** crc logic from rfc2083 ported to Javascript
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**--------------------------------------------------------------------------*/
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var rfc2083_crc_table = Array(256);
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var rfc2083_crc_table_computed = 0;
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/* Make the table for a fast CRC. */
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function rfc2083_make_crc_table()
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{
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var c;
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var n, k;
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for (n = 0; n < 256; n++)
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{
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c = n;
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for (k = 0; k < 8; k++)
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{
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if (c & 1)
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c = ((0xedb88320 ^ (c >>> 1)) >>> 0) & 0xffffffff;
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else
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c = c >>> 1;
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}
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rfc2083_crc_table[n] = c;
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}
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rfc2083_crc_table_computed = 1;
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}
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/* Update a running CRC with the bytes buf[0..len-1]--the CRC
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should be initialized to all 1's, and the transmitted value
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is the 1's complement of the final running CRC (see the
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crc() routine below)). */
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function rfc2083_update_crc(crc, u8buf, at, len)
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{
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var c = crc;
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var n;
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if (!rfc2083_crc_table_computed)
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rfc2083_make_crc_table();
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for (n = 0; n < len; n++)
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{
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c = rfc2083_crc_table[(c ^ u8buf[at + n]) & 0xff] ^ (c >>> 8);
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}
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return c;
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}
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function rfc2083_crc(u8buf, at, len)
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{
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return rfc2083_update_crc(0xffffffff, u8buf, at, len) ^ 0xffffffff;
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}
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function crc32(mb, at, len)
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{
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var u8 = new Uint8Array(mb);
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return rfc2083_crc(u8, at, len);
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}
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function PngIHDR(width, height)
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{
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this.width = width;
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this.height = height;
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this.depth = 8;
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this.type = 6;
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this.compression = 0;
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this.filter = 0;
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this.interlace = 0;
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}
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PngIHDR.prototype =
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{
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to_buffer: function(a, at)
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{
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at = at || 0;
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var orig = at;
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var dv = new SpiceDataView(a);
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dv.setUint32(at, this.buffer_size() - 12); at += 4;
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dv.setUint8(at, 'I'.charCodeAt(0)); at++;
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dv.setUint8(at, 'H'.charCodeAt(0)); at++;
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dv.setUint8(at, 'D'.charCodeAt(0)); at++;
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dv.setUint8(at, 'R'.charCodeAt(0)); at++;
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dv.setUint32(at, this.width); at += 4;
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dv.setUint32(at, this.height); at += 4;
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dv.setUint8(at, this.depth); at++;
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dv.setUint8(at, this.type); at++;
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dv.setUint8(at, this.compression); at++;
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dv.setUint8(at, this.filter); at++;
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dv.setUint8(at, this.interlace); at++;
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dv.setUint32(at, crc32(a, orig + 4, this.buffer_size() - 8)); at += 4;
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return at;
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},
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buffer_size: function()
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{
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return 12 + 13;
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}
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}
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function adler()
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{
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this.s1 = 1;
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this.s2 = 0;
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}
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adler.prototype.update = function(b)
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{
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this.s1 += b;
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this.s1 %= 65521;
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this.s2 += this.s1;
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this.s2 %= 65521;
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}
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function PngIDAT(width, height, bytes)
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{
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if (bytes.byteLength > 65535)
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{
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throw new Error("Cannot handle more than 64K");
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}
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this.data = bytes;
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this.width = width;
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this.height = height;
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}
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PngIDAT.prototype =
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{
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to_buffer: function(a, at)
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{
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at = at || 0;
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var orig = at;
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var x, y, i, j;
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var dv = new SpiceDataView(a);
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var zsum = new adler();
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dv.setUint32(at, this.buffer_size() - 12); at += 4;
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dv.setUint8(at, 'I'.charCodeAt(0)); at++;
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dv.setUint8(at, 'D'.charCodeAt(0)); at++;
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dv.setUint8(at, 'A'.charCodeAt(0)); at++;
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dv.setUint8(at, 'T'.charCodeAt(0)); at++;
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/* zlib header. */
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dv.setUint8(at, 0x78); at++;
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dv.setUint8(at, 0x01); at++;
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/* Deflate header. Specifies uncompressed, final bit */
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dv.setUint8(at, 0x80); at++;
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dv.setUint16(at, this.data.byteLength + this.height); at += 2;
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dv.setUint16(at, ~(this.data.byteLength + this.height)); at += 2;
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var u8 = new Uint8Array(this.data);
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for (i = 0, y = 0; y < this.height; y++)
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{
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/* Filter type 0 - uncompressed */
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dv.setUint8(at, 0); at++;
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zsum.update(0);
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for (x = 0; x < this.width && i < this.data.byteLength; x++)
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{
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zsum.update(u8[i]);
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dv.setUint8(at, u8[i++]); at++;
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zsum.update(u8[i]);
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dv.setUint8(at, u8[i++]); at++;
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zsum.update(u8[i]);
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dv.setUint8(at, u8[i++]); at++;
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zsum.update(u8[i]);
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dv.setUint8(at, u8[i++]); at++;
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}
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}
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/* zlib checksum. */
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dv.setUint16(at, zsum.s2); at+=2;
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dv.setUint16(at, zsum.s1); at+=2;
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/* FIXME - something is not quite right with the zlib code;
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you get an error from libpng if you open the image in
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gimp. But it works, so it's good enough for now... */
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dv.setUint32(at, crc32(a, orig + 4, this.buffer_size() - 8)); at += 4;
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return at;
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},
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buffer_size: function()
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{
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return 12 + this.data.byteLength + this.height + 4 + 2 + 1 + 2 + 2;
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}
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}
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function PngIEND()
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{
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}
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PngIEND.prototype =
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{
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to_buffer: function(a, at)
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{
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at = at || 0;
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var orig = at;
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var i;
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var dv = new SpiceDataView(a);
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dv.setUint32(at, this.buffer_size() - 12); at += 4;
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dv.setUint8(at, 'I'.charCodeAt(0)); at++;
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dv.setUint8(at, 'E'.charCodeAt(0)); at++;
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dv.setUint8(at, 'N'.charCodeAt(0)); at++;
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dv.setUint8(at, 'D'.charCodeAt(0)); at++;
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dv.setUint32(at, crc32(a, orig + 4, this.buffer_size() - 8)); at += 4;
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return at;
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},
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buffer_size: function()
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{
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return 12;
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}
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}
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function create_rgba_png(width, height, bytes)
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{
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var i;
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var ihdr = new PngIHDR(width, height);
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var idat = new PngIDAT(width, height, bytes);
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var iend = new PngIEND;
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var mb = new ArrayBuffer(ihdr.buffer_size() + idat.buffer_size() + iend.buffer_size());
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var at = ihdr.to_buffer(mb);
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at = idat.to_buffer(mb, at);
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at = iend.to_buffer(mb, at);
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var u8 = new Uint8Array(mb);
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var str = "";
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for (i = 0; i < at; i++)
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{
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str += "%";
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if (u8[i] < 16)
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str += "0";
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str += u8[i].toString(16);
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}
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return "%89PNG%0D%0A%1A%0A" + str;
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}
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