Repe [T3DU] Update - 31f26d171bba0355ce2a77031e3aad4c64dbc7e9
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350
leenkx/Sources/iron/format/gif/LzwEncoder.hx
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350
leenkx/Sources/iron/format/gif/LzwEncoder.hx
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package iron.format.gif;
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/*
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* No copyright asserted on the source code of this class. May be used
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* for any purpose, however, refer to the Unisys LZW patent for restrictions
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* on use of the associated LZWEncoder class :
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*
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* The Unisys patent expired on 20 June 2003 in the USA, in Europe it expired
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* on 18 June 2004, in Japan the patent expired on 20 June 2004 and in Canada
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* it expired on 7 July 2004. The U.S. IBM patent expired 11 August 2006, The
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* Software Freedom Law Center says that after 1 October 2006, there will be
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* no significant patent claims interfering with employment of the GIF format.
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*
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* Original code by Kevin Weiner, FM Software.
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* Adapted from Jef Poskanzer's Java port by way of J. M. G. Elliott.
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* Ported to Haxe by Tilman Schmidt and Sven Bergstr├╢m
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*
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*/
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import haxe.io.Int32Array;
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import haxe.io.UInt8Array;
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class LzwEncoder {
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static var EOF(default, never):Int = -1;
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var pixAry:UInt8Array;
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var initCodeSize:Int;
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var curPixel:Int;
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// GIFCOMPR.C - GIF Image compression routines
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//
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// Lempel-Ziv compression based on 'compress'. GIF modifications by
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// David Rowley (mgardi@watdcsu.waterloo.edu)
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// General DEFINEs
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static var BITS(default, never):Int = 12;
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static var HSIZE(default, never):Int = 5003; // 80% occupancy
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// GIF Image compression - modified 'compress'
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//
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// Based on: compress.c - File compression ala IEEE Computer, June 1984.
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//
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// By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
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// Jim McKie (decvax!mcvax!jim)
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// Steve Davies (decvax!vax135!petsd!peora!srd)
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// Ken Turkowski (decvax!decwrl!turtlevax!ken)
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// James A. Woods (decvax!ihnp4!ames!jaw)
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// Joe Orost (decvax!vax135!petsd!joe)
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var n_bits:Int; // number of bits/code
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var maxbits:Int = BITS; // user settable max # bits/code
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var maxcode:Int; // maximum code, given n_bits
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var maxmaxcode:Int = 1 << BITS; // should NEVER generate this code
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var htab:Int32Array;
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var codetab:Int32Array;
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var hsize:Int = HSIZE; // for dynamic table sizing
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var free_ent:Int = 0; // first unused entry
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// block compression parameters -- after all codes are used up,
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// and compression rate changes, start over.
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var clear_flg:Bool = false;
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// Algorithm: use open addressing double hashing (no chaining) on the
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// prefix code / next character combination. We do a variant of Knuth's
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// algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
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// secondary probe. Here, the modular division first probe is gives way
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// to a faster exclusive-or manipulation. Also do block compression with
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// an adaptive reset, whereby the code table is cleared when the compression
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// ratio decreases, but after the table fills. The variable-length output
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// codes are re-sized at this point, and a special CLEAR code is generated
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// for the decompressor. Late addition: construct the table according to
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// file size for noticeable speed improvement on small files. Please direct
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// questions about this implementation to ames!jaw.
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var g_init_bits:Int;
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var ClearCode:Int;
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var EOFCode:Int;
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// output
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//
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// output the given code.
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// Inputs:
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// code: A n_bits-bit integer. If == -1, then EOF. This assumes
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// that n_bits =< wordsize - 1.
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// outputs:
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// outputs code to the file.
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// Assumptions:
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// Chars are 8 bits long.
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// Algorithm:
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// Maintain a BITS character long buffer (so that 8 codes will
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// fit in it exactly). Use the VAX insv instruction to insert each
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// code in turn. When the buffer fills up empty it and start over.
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var cur_accum:Int = 0;
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var cur_bits:Int = 0;
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var masks:Array<Int> =
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[
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0x0000,
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0x0001,
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0x0003,
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0x0007,
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0x000F,
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0x001F,
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0x003F,
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0x007F,
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0x00FF,
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0x01FF,
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0x03FF,
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0x07FF,
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0x0FFF,
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0x1FFF,
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0x3FFF,
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0x7FFF,
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0xFFFF ];
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// Number of characters so far in this 'packet'
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var a_count:Int;
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// Define the storage for the packet accumulator
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var accum:UInt8Array;
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//----------------------------------------------------------------------------
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public function new()
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{
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htab = new Int32Array(HSIZE);
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codetab = new Int32Array(HSIZE);
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accum = new UInt8Array(256);
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}
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//Reset the encoder to new pixel data and default values
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public function reset(pixels:UInt8Array, color_depth:Int) { //width and height used to be passed in though they were never used
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pixAry = pixels;
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initCodeSize = Std.int(Math.max(2, color_depth));
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maxbits = BITS;
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maxmaxcode = 1 << BITS;
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hsize = HSIZE;
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free_ent = 0;
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clear_flg = false;
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cur_accum = 0;
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cur_bits = 0;
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}
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// add a character to the end of the current packet, and if it is 254
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// characters, flush the packet to disk.
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function add(c:UInt, out:haxe.io.Output):Void
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{
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accum[a_count++] = c;
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if (a_count >= 254)
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flush(out);
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}
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// Clear out the hash table
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// table clear for block compress
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function clearTable(out:haxe.io.Output):Void
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{
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resetCodeTable(hsize);
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free_ent = ClearCode + 2;
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clear_flg = true;
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output(ClearCode, out);
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}
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// reset code table
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function resetCodeTable(hsize:Int):Void
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{
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for (i in 0...hsize)
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htab[i] = -1;
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}
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function compress(init_bits:Int, out:haxe.io.Output):Void
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{
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var fcode:Int;
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var i:Int /* = 0 */;
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var c:Int;
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var ent:Int;
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var disp:Int;
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var hsize_reg:Int;
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var hshift:Int;
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// Set up the globals: g_init_bits - initial number of bits
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g_init_bits = init_bits;
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// Set up the necessary values
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clear_flg = false;
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n_bits = g_init_bits;
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maxcode = maxCode(n_bits);
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ClearCode = 1 << (init_bits - 1);
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EOFCode = ClearCode + 1;
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free_ent = ClearCode + 2;
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a_count = 0; // clear packet
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ent = nextPixel();
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hshift = 0;
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fcode = hsize;
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while (fcode < 65536) {
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++hshift;
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fcode *= 2;
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}
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hshift = 8 - hshift; // set hash code range bound
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hsize_reg = hsize;
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resetCodeTable(hsize_reg); // clear hash table
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output(ClearCode, out);
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while ((c = nextPixel()) != EOF)
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{
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fcode = (c << maxbits) + ent;
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i = (c << hshift) ^ ent; // xor hashing
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if (htab[i] == fcode)
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{
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ent = codetab[i];
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continue;
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}
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else if (htab[i] >= 0) // non-empty slot
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{
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disp = hsize_reg - i; // secondary hash (after G. Knott)
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if (i == 0)
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disp = 1;
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do
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{
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if ((i -= disp) < 0)
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i += hsize_reg;
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if (htab[i] == fcode)
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{
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ent = codetab[i];
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break;
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}
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} while (htab[i] >= 0);
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if (htab[i] == fcode) continue;
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}
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output(ent, out);
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ent = c;
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if (free_ent < maxmaxcode)
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{
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codetab[i] = free_ent++; // code -> hashtable
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htab[i] = fcode;
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}
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else
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clearTable(out);
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}
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// Put out the final code.
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output(ent, out);
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output(EOFCode, out);
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}
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//----------------------------------------------------------------------------
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public function encode(os:haxe.io.Output):Void
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{
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os.writeByte( initCodeSize ); // write "initial code size" byte
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curPixel = 0;
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compress(initCodeSize + 1, os); // compress and write the pixel data
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os.writeByte(0); // write block terminator
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}
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// flush the packet to disk, and reset the accumulator
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function flush(out:haxe.io.Output):Void
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{
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if (a_count > 0)
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{
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out.writeByte(a_count);
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out.writeBytes(accum.view.buffer, 0, a_count);
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a_count = 0;
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}
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}
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inline function maxCode(n_bits:Int):Int
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{
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return (1 << n_bits) - 1;
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}
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//----------------------------------------------------------------------------
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// Return the next pixel from the image
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//----------------------------------------------------------------------------
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function nextPixel():Int
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{
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if (curPixel == pixAry.length)
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return EOF;
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curPixel++;
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return pixAry[curPixel - 1] & 0xff;
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}
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function output(code:Int, out:haxe.io.Output):Void
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{
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cur_accum &= masks[cur_bits];
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if (cur_bits > 0)
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cur_accum |= (code << cur_bits);
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else
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cur_accum = code;
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cur_bits += n_bits;
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while (cur_bits >= 8)
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{
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add(cur_accum & 0xff, out);
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cur_accum >>= 8;
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cur_bits -= 8;
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}
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// If the next entry is going to be too big for the code size,
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// then increase it, if possible.
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if (free_ent > maxcode || clear_flg)
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{
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if (clear_flg)
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{
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maxcode = maxCode(n_bits = g_init_bits);
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clear_flg = false;
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}
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else
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{
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++n_bits;
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if (n_bits == maxbits)
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maxcode = maxmaxcode;
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else
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maxcode = maxCode(n_bits);
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}
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}
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if (code == EOFCode)
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{
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// At EOF, write the rest of the buffer.
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while (cur_bits > 0)
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{
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add(cur_accum & 0xff, out);
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cur_accum >>= 8;
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cur_bits -= 8;
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}
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flush(out);
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}
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}
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}
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