587 lines
14 KiB
C
587 lines
14 KiB
C
/*
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* xvgifwr.c - handles writing of GIF files. based on flgife.c and
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* flgifc.c from the FBM Library, by Michael Maudlin
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*
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* Contains:
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* WriteGIF(fp, pic, w, h, rmap, gmap, bmap, numcols, colorstyle)
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*
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* Note: slightly brain-damaged, in that it'll only write non-interlaced
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* GIF files (in the interests of speed, or something)
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*
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*/
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/*****************************************************************
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* Portions of this code Copyright (C) 1989 by Michael Mauldin.
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* Permission is granted to use this file in whole or in
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* part for any purpose, educational, recreational or commercial,
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* provided that this copyright notice is retained unchanged.
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* This software is available to all free of charge by anonymous
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* FTP and in the UUNET archives.
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*
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*
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* Authors: Michael Mauldin (mlm@cs.cmu.edu)
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* David Rowley (mgardi@watdcsu.waterloo.edu)
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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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* 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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*****************************************************************/
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/*
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* Copyright 1989, 1990, 1991, 1992 by John Bradley and
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* The University of Pennsylvania
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*
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* Permission to use, copy, and distribute for non-commercial purposes,
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* is hereby granted without fee, providing that the above copyright
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* notice appear in all copies and that both the copyright notice and this
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* permission notice appear in supporting documentation.
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*
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* The software may be modified for your own purposes, but modified versions
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* may not be distributed.
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*
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* This software is provided "as is" without any expressed or implied warranty.
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*
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* The author may be contacted via:
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* US Mail: John Bradley
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* GRASP Lab, Room 301C
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* 3401 Walnut St.
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* Philadelphia, PA 19104
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*
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* Phone: (215) 898-8813
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* EMail: bradley@cis.upenn.edu
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*/
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#include "xv.h"
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typedef long int count_int;
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static int Width, Height;
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static int curx, cury;
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static long CountDown;
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static int Interlace;
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static byte bw[2] = {0, 0xff};
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#ifdef __STDC__
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static void putword(int, FILE *);
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static void compress(int, FILE *, byte *, int);
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static void output(int);
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static void cl_block(void);
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static void cl_hash(count_int);
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static void char_init(void);
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static void char_out(int);
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static void flush_char(void);
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#else
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static void putword(), compress(), output(), cl_block(), cl_hash();
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static void char_init(), char_out(), flush_char();
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#endif
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static byte pc2nc[256],r1[256],g1[256],b1[256];
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/*************************************************************/
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int WriteGIF(fp, pic, w, h, rmap, gmap, bmap, numcols, colorstyle)
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FILE *fp;
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byte *pic;
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int w,h;
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byte *rmap, *gmap, *bmap;
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int numcols, colorstyle;
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{
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int RWidth, RHeight;
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int LeftOfs, TopOfs;
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int ColorMapSize, InitCodeSize, Background, BitsPerPixel;
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int i,j,nc;
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/* if writing B/W stipple... */
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if (colorstyle==2) {
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rmap = gmap = bmap = bw;
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numcols = 2;
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}
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Interlace = 0;
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Background = 0;
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for (i=0; i<256; i++) { pc2nc[i] = r1[i] = g1[i] = b1[i] = 0; }
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/* compute number of unique colors */
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nc = 0;
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for (i=0; i<numcols; i++) {
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/* see if color #i is already used */
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for (j=0; j<i; j++) {
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if (rmap[i] == rmap[j] && gmap[i] == gmap[j] &&
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bmap[i] == bmap[j]) break;
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}
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if (j==i) { /* wasn't found */
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pc2nc[i] = nc;
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r1[nc] = rmap[i];
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g1[nc] = gmap[i];
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b1[nc] = bmap[i];
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nc++;
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}
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else pc2nc[i] = pc2nc[j];
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}
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/* figure out 'BitsPerPixel' */
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for (i=1; i<8; i++)
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if ( (1<<i) >= nc) break;
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BitsPerPixel = i;
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ColorMapSize = 1 << BitsPerPixel;
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RWidth = Width = w;
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RHeight = Height = h;
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LeftOfs = TopOfs = 0;
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CountDown = w * h; /* # of pixels we'll be doing */
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if (BitsPerPixel <= 1) InitCodeSize = 2;
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else InitCodeSize = BitsPerPixel;
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curx = cury = 0;
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if (!fp) {
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fprintf(stderr, "WriteGIF: file not open for writing\n" );
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return (1);
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}
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fwrite("GIF87a", 1, 6, fp); /* the GIF magic number */
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putword(RWidth, fp); /* screen descriptor */
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putword(RHeight, fp);
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i = 0x80; /* Yes, there is a color map */
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i |= (8-1)<<4; /* OR in the color resolution (hardwired 8) */
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i |= (BitsPerPixel - 1); /* OR in the # of bits per pixel */
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fputc(i,fp);
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fputc(Background, fp); /* background color */
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fputc(0, fp); /* future expansion byte */
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if (colorstyle == 1) { /* greyscale */
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for (i=0; i<ColorMapSize; i++) {
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j = MONO(r1[i], g1[i], b1[i]);
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fputc(j, fp);
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fputc(j, fp);
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fputc(j, fp);
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}
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}
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else {
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for (i=0; i<ColorMapSize; i++) { /* write out Global colormap */
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fputc(r1[i], fp);
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fputc(g1[i], fp);
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fputc(b1[i], fp);
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}
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}
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fputc( ',', fp ); /* image separator */
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/* Write the Image header */
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putword(LeftOfs, fp);
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putword(TopOfs, fp);
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putword(Width, fp);
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putword(Height, fp);
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if (Interlace) fputc(0x40, fp); /* Use Global Colormap, maybe Interlace */
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else fputc(0x00, fp);
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fputc(InitCodeSize, fp);
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compress(InitCodeSize+1, fp, pic, w*h);
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fputc(0,fp); /* Write out a Zero-length packet (EOF) */
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fputc(';',fp); /* Write GIF file terminator */
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return (0);
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}
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/******************************/
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static void putword(w, fp)
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int w;
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FILE *fp;
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{
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/* writes a 16-bit integer in GIF order (LSB first) */
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fputc(w & 0xff, fp);
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fputc((w>>8)&0xff, fp);
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}
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/***********************************************************************/
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static unsigned long cur_accum = 0;
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static int cur_bits = 0;
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#define min(a,b) ((a>b) ? b : a)
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#define XV_BITS 12 /* BITS was already defined on some systems */
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#define MSDOS 1
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#define HSIZE 5003 /* 80% occupancy */
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typedef unsigned char char_type;
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static int n_bits; /* number of bits/code */
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static int maxbits = XV_BITS; /* user settable max # bits/code */
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static int maxcode; /* maximum code, given n_bits */
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static int maxmaxcode = 1 << XV_BITS; /* NEVER generate this */
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#define MAXCODE(n_bits) ( (1 << (n_bits)) - 1)
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static count_int htab [HSIZE];
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static unsigned short codetab [HSIZE];
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#define HashTabOf(i) htab[i]
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#define CodeTabOf(i) codetab[i]
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static int hsize = HSIZE; /* for dynamic table sizing */
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/*
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* To save much memory, we overlay the table used by compress() with those
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* used by decompress(). The tab_prefix table is the same size and type
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* as the codetab. The tab_suffix table needs 2**BITS characters. We
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* get this from the beginning of htab. The output stack uses the rest
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* of htab, and contains characters. There is plenty of room for any
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* possible stack (stack used to be 8000 characters).
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*/
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#define tab_prefixof(i) CodeTabOf(i)
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#define tab_suffixof(i) ((char_type *)(htab))[i]
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#define de_stack ((char_type *)&tab_suffixof(1<<XV_BITS))
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static int free_ent = 0; /* first unused entry */
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/*
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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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*/
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static int clear_flg = 0;
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static long int in_count = 1; /* length of input */
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static long int out_count = 0; /* # of codes output (for debugging) */
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/*
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* compress stdin to stdout
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*
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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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*/
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static int g_init_bits;
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static FILE *g_outfile;
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static int ClearCode;
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static int EOFCode;
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/********************************************************/
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static void compress(init_bits, outfile, data, len)
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int init_bits;
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FILE *outfile;
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byte *data;
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int len;
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{
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register long fcode;
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register int i = 0;
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register int c;
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register int ent;
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register int disp;
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register int hsize_reg;
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register int hshift;
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/*
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* Set up the globals: g_init_bits - initial number of bits
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* g_outfile - pointer to output file
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*/
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g_init_bits = init_bits;
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g_outfile = outfile;
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/* initialize 'compress' globals */
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maxbits = XV_BITS;
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maxmaxcode = 1<<XV_BITS;
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memset((char *) htab, 0, sizeof(htab));
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memset((char *) codetab, 0, sizeof(codetab));
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hsize = HSIZE;
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free_ent = 0;
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clear_flg = 0;
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in_count = 1;
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out_count = 0;
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cur_accum = 0;
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cur_bits = 0;
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/*
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* Set up the necessary values
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*/
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out_count = 0;
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clear_flg = 0;
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in_count = 1;
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maxcode = MAXCODE(n_bits = g_init_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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char_init();
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ent = pc2nc[*data++]; len--;
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hshift = 0;
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for ( fcode = (long) hsize; fcode < 65536L; fcode *= 2L )
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hshift++;
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hshift = 8 - hshift; /* set hash code range bound */
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hsize_reg = hsize;
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cl_hash( (count_int) hsize_reg); /* clear hash table */
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output(ClearCode);
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while (len) {
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c = pc2nc[*data++]; len--;
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in_count++;
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fcode = (long) ( ( (long) c << maxbits) + ent);
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i = (((int) c << hshift) ^ ent); /* xor hashing */
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if ( HashTabOf (i) == fcode ) {
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ent = CodeTabOf (i);
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continue;
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}
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else if ( (long)HashTabOf (i) < 0 ) /* empty slot */
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goto nomatch;
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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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probe:
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if ( (i -= disp) < 0 )
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i += hsize_reg;
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if ( HashTabOf (i) == fcode ) {
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ent = CodeTabOf (i);
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continue;
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}
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if ( (long)HashTabOf (i) > 0 )
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goto probe;
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nomatch:
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output(ent);
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out_count++;
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ent = c;
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if ( free_ent < maxmaxcode ) {
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CodeTabOf (i) = free_ent++; /* code -> hashtable */
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HashTabOf (i) = fcode;
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}
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else
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cl_block();
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}
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/* Put out the final code */
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output(ent);
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out_count++;
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output(EOFCode);
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}
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/*****************************************************************
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* TAG( 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 =< (long)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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*/
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static
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unsigned long masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
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0x001F, 0x003F, 0x007F, 0x00FF,
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0x01FF, 0x03FF, 0x07FF, 0x0FFF,
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0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };
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static void output(code)
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int code;
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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 |= ((long)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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char_out( (unsigned int) (cur_accum & 0xff) );
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cur_accum >>= 8;
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cur_bits -= 8;
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}
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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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*/
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if (free_ent > maxcode || clear_flg) {
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if( clear_flg ) {
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maxcode = MAXCODE (n_bits = g_init_bits);
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clear_flg = 0;
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}
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else {
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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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/* At EOF, write the rest of the buffer */
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while( cur_bits > 0 ) {
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char_out( (unsigned int)(cur_accum & 0xff) );
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cur_accum >>= 8;
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cur_bits -= 8;
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}
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flush_char();
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fflush( g_outfile );
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}
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}
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/********************************/
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static void cl_block () /* table clear for block compress */
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{
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/* Clear out the hash table */
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cl_hash ( (count_int) hsize );
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free_ent = ClearCode + 2;
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clear_flg = 1;
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output(ClearCode);
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}
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/********************************/
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static void cl_hash(hsize) /* reset code table */
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register count_int hsize;
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{
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register count_int *htab_p = htab+hsize;
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register long i;
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register long m1 = -1;
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i = hsize - 16;
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do { /* might use Sys V memset(3) here */
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*(htab_p-16) = m1;
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*(htab_p-15) = m1;
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*(htab_p-14) = m1;
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*(htab_p-13) = m1;
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*(htab_p-12) = m1;
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*(htab_p-11) = m1;
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*(htab_p-10) = m1;
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*(htab_p-9) = m1;
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*(htab_p-8) = m1;
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*(htab_p-7) = m1;
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*(htab_p-6) = m1;
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*(htab_p-5) = m1;
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*(htab_p-4) = m1;
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*(htab_p-3) = m1;
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*(htab_p-2) = m1;
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*(htab_p-1) = m1;
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htab_p -= 16;
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} while ((i -= 16) >= 0);
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for ( i += 16; i > 0; i-- )
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*--htab_p = m1;
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}
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/******************************************************************************
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*
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* GIF Specific routines
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*
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******************************************************************************/
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/*
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* Number of characters so far in this 'packet'
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*/
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static int a_count;
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/*
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* Set up the 'byte output' routine
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*/
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static void char_init()
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{
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|
a_count = 0;
|
|
}
|
|
|
|
/*
|
|
* Define the storage for the packet accumulator
|
|
*/
|
|
static char accum[ 256 ];
|
|
|
|
/*
|
|
* Add a character to the end of the current packet, and if it is 254
|
|
* characters, flush the packet to disk.
|
|
*/
|
|
static void char_out(c)
|
|
int c;
|
|
{
|
|
accum[ a_count++ ] = c;
|
|
if( a_count >= 254 )
|
|
flush_char();
|
|
}
|
|
|
|
/*
|
|
* Flush the packet to disk, and reset the accumulator
|
|
*/
|
|
static void flush_char()
|
|
{
|
|
if( a_count > 0 ) {
|
|
fputc( a_count, g_outfile );
|
|
fwrite( accum, 1, a_count, g_outfile );
|
|
a_count = 0;
|
|
}
|
|
}
|