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Diffstat (limited to 'js/vendor/gif-encode/LZWEncoder.js')
| -rw-r--r-- | js/vendor/gif-encode/LZWEncoder.js | 328 |
1 files changed, 328 insertions, 0 deletions
diff --git a/js/vendor/gif-encode/LZWEncoder.js b/js/vendor/gif-encode/LZWEncoder.js new file mode 100644 index 0000000..e3c512a --- /dev/null +++ b/js/vendor/gif-encode/LZWEncoder.js @@ -0,0 +1,328 @@ +/**
+* This class handles LZW encoding
+* Adapted from Jef Poskanzer's Java port by way of J. M. G. Elliott.
+* @author Kevin Weiner (original Java version - kweiner@fmsware.com)
+* @author Thibault Imbert (AS3 version - bytearray.org)
+* @version 0.1 AS3 implementation
+*/
+
+//import flash.utils.ByteArray;
+
+LZWEncoder = function()
+{
+ var exports = {};
+ /*private_static*/ var EOF/*int*/ = -1;
+ /*private*/ var imgW/*int*/;
+ /*private*/ var imgH/*int*/
+ /*private*/ var pixAry/*ByteArray*/;
+ /*private*/ var initCodeSize/*int*/;
+ /*private*/ var remaining/*int*/;
+ /*private*/ var curPixel/*int*/;
+
+ // GIFCOMPR.C - GIF Image compression routines
+ // Lempel-Ziv compression based on 'compress'. GIF modifications by
+ // David Rowley (mgardi@watdcsu.waterloo.edu)
+ // General DEFINEs
+
+ /*private_static*/ var BITS/*int*/ = 12;
+ /*private_static*/ var HSIZE/*int*/ = 5003; // 80% occupancy
+
+ // GIF Image compression - modified 'compress'
+ // Based on: compress.c - File compression ala IEEE Computer, June 1984.
+ // By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
+ // Jim McKie (decvax!mcvax!jim)
+ // Steve Davies (decvax!vax135!petsd!peora!srd)
+ // Ken Turkowski (decvax!decwrl!turtlevax!ken)
+ // James A. Woods (decvax!ihnp4!ames!jaw)
+ // Joe Orost (decvax!vax135!petsd!joe)
+
+ /*private*/ var n_bits/*int*/ // number of bits/code
+ /*private*/ var maxbits/*int*/ = BITS; // user settable max # bits/code
+ /*private*/ var maxcode/*int*/ // maximum code, given n_bits
+ /*private*/ var maxmaxcode/*int*/ = 1 << BITS; // should NEVER generate this code
+ /*private*/ var htab/*Array*/ = new Array;
+ /*private*/ var codetab/*Array*/ = new Array;
+ /*private*/ var hsize/*int*/ = HSIZE; // for dynamic table sizing
+ /*private*/ var free_ent/*int*/ = 0; // first unused entry
+
+ // block compression parameters -- after all codes are used up,
+ // and compression rate changes, start over.
+
+ /*private*/ var clear_flg/*Boolean*/ = false;
+
+ // Algorithm: use open addressing double hashing (no chaining) on the
+ // prefix code / next character combination. We do a variant of Knuth's
+ // algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
+ // secondary probe. Here, the modular division first probe is gives way
+ // to a faster exclusive-or manipulation. Also do block compression with
+ // an adaptive reset, whereby the code table is cleared when the compression
+ // ratio decreases, but after the table fills. The variable-length output
+ // codes are re-sized at this point, and a special CLEAR code is generated
+ // for the decompressor. Late addition: construct the table according to
+ // file size for noticeable speed improvement on small files. Please direct
+ // questions about this implementation to ames!jaw.
+
+ /*private*/ var g_init_bits/*int*/;
+ /*private*/ var ClearCode/*int*/;
+ /*private*/ var EOFCode/*int*/;
+
+ // output
+ // Output the given code.
+ // Inputs:
+ // code: A n_bits-bit integer. If == -1, then EOF. This assumes
+ // that n_bits =< wordsize - 1.
+ // Outputs:
+ // Outputs code to the file.
+ // Assumptions:
+ // Chars are 8 bits long.
+ // Algorithm:
+ // Maintain a BITS character long buffer (so that 8 codes will
+ // fit in it exactly). Use the VAX insv instruction to insert each
+ // code in turn. When the buffer fills up empty it and start over.
+
+ /*private*/ var cur_accum/*int*/ = 0;
+ /*private*/ var cur_bits/*int*/ = 0;
+ /*private*/ var masks/*Array*/ = [ 0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, 0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF ];
+
+ // Number of characters so far in this 'packet'
+ /*private*/ var a_count/*int*/;
+
+ // Define the storage for the packet accumulator
+ /*private*/ var accum/*ByteArray*/ = [];
+
+ var LZWEncoder = exports.LZWEncoder = function LZWEncoder (width/*int*/, height/*int*/, pixels/*ByteArray*/, color_depth/*int*/)
+ {
+
+ imgW = width;
+ imgH = height;
+ pixAry = pixels;
+ initCodeSize = Math.max(2, color_depth);
+
+ }
+
+ // Add a character to the end of the current packet, and if it is 254
+ // characters, flush the packet to disk.
+ var char_out = function char_out(c/*Number*/, outs/*ByteArray*/)/*void*/
+ {
+ accum[a_count++] = c;
+ if (a_count >= 254) flush_char(outs);
+
+ }
+
+ // Clear out the hash table
+ // table clear for block compress
+
+ var cl_block = function cl_block(outs/*ByteArray*/)/*void*/
+ {
+
+ cl_hash(hsize);
+ free_ent = ClearCode + 2;
+ clear_flg = true;
+ output(ClearCode, outs);
+
+ }
+
+ // reset code table
+ var cl_hash = function cl_hash(hsize/*int*/)/*void*/
+ {
+
+ for (var i/*int*/ = 0; i < hsize; ++i) htab[i] = -1;
+
+ }
+
+ var compress = exports.compress = function compress(init_bits/*int*/, outs/*ByteArray*/)/*void*/
+
+ {
+ var fcode/*int*/;
+ var i/*int*/ /* = 0 */;
+ var c/*int*/;
+ var ent/*int*/;
+ var disp/*int*/;
+ var hsize_reg/*int*/;
+ var hshift/*int*/;
+
+ // Set up the globals: g_init_bits - initial number of bits
+ g_init_bits = init_bits;
+
+ // Set up the necessary values
+ clear_flg = false;
+ n_bits = g_init_bits;
+ maxcode = MAXCODE(n_bits);
+
+ ClearCode = 1 << (init_bits - 1);
+ EOFCode = ClearCode + 1;
+ free_ent = ClearCode + 2;
+
+ a_count = 0; // clear packet
+
+ ent = nextPixel();
+
+ hshift = 0;
+ for (fcode = hsize; fcode < 65536; fcode *= 2)
+ ++hshift;
+ hshift = 8 - hshift; // set hash code range bound
+
+ hsize_reg = hsize;
+ cl_hash(hsize_reg); // clear hash table
+
+ output(ClearCode, outs);
+
+ outer_loop: while ((c = nextPixel()) != EOF)
+
+ {
+
+ fcode = (c << maxbits) + ent;
+ i = (c << hshift) ^ ent; // xor hashing
+
+ if (htab[i] == fcode)
+ {
+ ent = codetab[i];
+ continue;
+ } else if (htab[i] >= 0) // non-empty slot
+ {
+ disp = hsize_reg - i; // secondary hash (after G. Knott)
+ if (i == 0)
+ disp = 1;
+ do
+ {
+
+ if ((i -= disp) < 0) i += hsize_reg;
+
+ if (htab[i] == fcode)
+ {
+ ent = codetab[i];
+ continue outer_loop;
+ }
+ } while (htab[i] >= 0);
+ }
+
+ output(ent, outs);
+ ent = c;
+ if (free_ent < maxmaxcode)
+ {
+ codetab[i] = free_ent++; // code -> hashtable
+ htab[i] = fcode;
+ } else cl_block(outs);
+ }
+
+ // Put out the final code.
+ output(ent, outs);
+ output(EOFCode, outs);
+
+ }
+
+ // ----------------------------------------------------------------------------
+ var encode = exports.encode = function encode(os/*ByteArray*/)/*void*/
+ {
+ os.writeByte(initCodeSize); // write "initial code size" byte
+ remaining = imgW * imgH; // reset navigation variables
+ curPixel = 0;
+ compress(initCodeSize + 1, os); // compress and write the pixel data
+ os.writeByte(0); // write block terminator
+
+ }
+
+ // Flush the packet to disk, and reset the accumulator
+ var flush_char = function flush_char(outs/*ByteArray*/)/*void*/
+ {
+
+ if (a_count > 0)
+ {
+ outs.writeByte(a_count);
+ outs.writeBytes(accum, 0, a_count);
+ a_count = 0;
+ }
+
+ }
+
+ var MAXCODE = function MAXCODE(n_bits/*int*/)/*int*/
+ {
+
+ return (1 << n_bits) - 1;
+
+ }
+
+ // ----------------------------------------------------------------------------
+ // Return the next pixel from the image
+ // ----------------------------------------------------------------------------
+
+ var nextPixel = function nextPixel()/*int*/
+ {
+
+ if (remaining == 0) return EOF;
+
+ --remaining;
+
+ var pix/*Number*/ = pixAry[curPixel++];
+
+ return pix & 0xff;
+
+ }
+
+ var output = function output(code/*int*/, outs/*ByteArray*/)/*void*/
+
+ {
+ cur_accum &= masks[cur_bits];
+
+ if (cur_bits > 0) cur_accum |= (code << cur_bits);
+ else cur_accum = code;
+
+ cur_bits += n_bits;
+
+ while (cur_bits >= 8)
+
+ {
+
+ char_out((cur_accum & 0xff), outs);
+ cur_accum >>= 8;
+ cur_bits -= 8;
+
+ }
+
+ // If the next entry is going to be too big for the code size,
+ // then increase it, if possible.
+
+ if (free_ent > maxcode || clear_flg)
+ {
+
+ if (clear_flg)
+ {
+
+ maxcode = MAXCODE(n_bits = g_init_bits);
+ clear_flg = false;
+
+ } else
+ {
+
+ ++n_bits;
+
+ if (n_bits == maxbits) maxcode = maxmaxcode;
+
+ else maxcode = MAXCODE(n_bits);
+
+ }
+
+ }
+
+ if (code == EOFCode)
+ {
+
+ // At EOF, write the rest of the buffer.
+ while (cur_bits > 0)
+ {
+
+ char_out((cur_accum & 0xff), outs);
+ cur_accum >>= 8;
+ cur_bits -= 8;
+ }
+
+
+ flush_char(outs);
+
+ }
+
+ }
+ LZWEncoder.apply(this, arguments);
+ return exports;
+}
+
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