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/* -----------------------------------------------------------------------------
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* GIF encoding with broken compression algorithm to avoid LZW.
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* Author(s) : David Beazley (beazley@cs.uchicago.edu)
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* Copyright (C) 1995-1996
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* See the file LICENSE for information on usage and redistribution.
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* ----------------------------------------------------------------------------- */
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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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* WriteGIF(fp, pic, ptype, w, h, rmap, gmap, bmap, numcols, colorstyle,
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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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* 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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* Authors: Michael Mauldin (mlm@cs.cmu.edu)
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* David Rowley (mgardi@watdcsu.waterloo.edu)
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* Based on: compress.c - File compression ala IEEE Computer, June 1984.
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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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typedef long int count_int;
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typedef unsigned char byte;
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static unsigned char *op;
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static int Width, Height;
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static int curx, cury;
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static void putgifword(int);
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static void compress(int, byte **, int);
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static void output_GIF(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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static void *OutBuffer;
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static int OutBufSize;
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static FrameBuffer *GIF_frame;
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static unsigned char pc2nc[256],r1[256],g1[256],b1[256];
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/*************************************************************/
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int FrameBuffer_makeGIF(FrameBuffer *f, ColorMap *c, void *outbuffer, unsigned int outbufsize)
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int ColorMapSize, InitCodeSize, Background, BitsPerPixel;
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char *rmap, *gmap, *bmap;
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OutBuffer = outbuffer;
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OutBufSize = outbufsize;
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cmap = (char *) c->cmap;
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op = (unsigned char *) outbuffer;
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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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for (i=0; i<256; 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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if (j==i) { /* wasn't found */
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else pc2nc[i] = pc2nc[j];
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/* figure out 'BitsPerPixel' */
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if ( (1<<i) >= nc) break;
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ColorMapSize = 1 << BitsPerPixel;
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RWidth = Width = f->width;
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RHeight = Height = f->height;
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LeftOfs = TopOfs = 0;
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if (BitsPerPixel <= 1) InitCodeSize = 2;
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else InitCodeSize = BitsPerPixel;
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cury = f->height - 1;
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strcpy((char *) op,"GIF89a"); /* Put in GIF magic number */
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putgifword(RWidth); /* screen descriptor */
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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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*(op++) = Background; /* background color */
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for (i=0; i<ColorMapSize; i++) { /* write out Global colormap */
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*(op++) = ','; /* image separator */
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/* Write the Image header */
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*(op++) = InitCodeSize;
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compress(InitCodeSize+1, f->pixels, f->width*f->height);
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count = (op - (unsigned char *) OutBuffer);
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if (gif_error) return -1;
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/******************************/
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static void putgifword(w)
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/* writes a 16-bit integer in GIF order (LSB first) */
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*(op++) = (w>>8)&0xff;
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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 GP_BITS 12 /* BITS was already defined on some systems */
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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 = GP_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 << GP_BITS; /* NEVER generate this */
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#define MAXCODE(n_bits) ( (1 << (n_bits)) - 1)
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static count_int *htab;
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static unsigned short *codetab;
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static GIFOutBufSize;
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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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* 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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#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<<GP_BITS))
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static int free_ent = 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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static int clear_flg = 0;
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static long int out_count = 0; /* # of codes output (for debugging) */
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* compress stdin to stdout
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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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static int g_init_bits;
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static int ClearCode;
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/********************************************************/
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static void compress(init_bits, data, len)
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unsigned char **data;
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register int hsize_reg;
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/* Use the output buffer as temporary storage for GIF data */
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if (OutBufSize < HSIZE*(sizeof(count_int) + sizeof(unsigned short))) {
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/* Put htab and codetab arrays into the output buffer */
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GIFOutBufSize = OutBufSize - HSIZE*(sizeof(count_int) + sizeof(unsigned short)) - 16;
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GIFOutBufSize = GIFOutBufSize & (~0x3); /* Make sure it's double word alligned */
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htab = (count_int *) ((char *) OutBuffer + GIFOutBufSize);
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codetab = (unsigned short *) ((char *) OutBuffer + GIFOutBufSize + HSIZE*sizeof(count_int));
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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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g_init_bits = init_bits;
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/* initialize 'compress' globals */
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maxmaxcode = 1<<GP_BITS;
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memset(htab,0,sizeof(htab));
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memset(codetab,0,sizeof(codetab));
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* Set up the necessary values
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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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ent = pc2nc[data[cury][curx]];
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if (curx >= GIF_frame->width) {
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for ( fcode = (long) hsize; fcode < 65536L; fcode *= 2L )
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hshift = 8 - hshift; /* set hash code range bound */
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cl_hash( (count_int) hsize_reg); /* clear hash table */
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output_GIF(ClearCode);
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c = pc2nc[data[cury][curx]];
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if (curx >= GIF_frame->width) {
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/* Uncompressed GIF */
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if (code_count >= ClearCode-2) {
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output_GIF(ClearCode);
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/* Put out the final code */
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/*****************************************************************
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* Output the given code.
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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 code to the file.
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* Chars are 8 bits long.
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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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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_GIF(code)
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cur_accum &= masks[cur_bits];
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cur_accum |= ((long)code << cur_bits);
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while( cur_bits >= 8 ) {
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char_out( (int) (cur_accum & 0xff) );
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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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maxcode = MAXCODE (n_bits = g_init_bits);
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if ( n_bits == maxbits )
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maxcode = maxmaxcode;
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maxcode = MAXCODE(n_bits);
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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( (int)(cur_accum & 0xff) );
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/********************************/
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static void cl_block () /* table clear for block compress */
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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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output_GIF(ClearCode);
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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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register count_int *htab_p = htab+hsize;
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register long m1 = -1;
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do { /* might use Sys V memset(3) here */
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} while ((i -= 16) >= 0);
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for ( i += 16; i > 0; i-- )
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/******************************************************************************
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* GIF Specific routines
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******************************************************************************/
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* Number of characters so far in this 'packet'
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* Set up the 'byte output' routine
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static void char_init()
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* Define the storage for the packet accumulator
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static char accum[ 256 ];
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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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static void char_out(c)
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accum[ a_count++ ] = c;
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* Flush the packet to disk, and reset the accumulator
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static void flush_char()
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if (gif_error) return;
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memcpy(op,accum,a_count);
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if (op > (unsigned char *) ((char *) OutBuffer + (GIFOutBufSize - 2048))) {
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/* ----------------------------------------------------------------------
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int FrameBuffer_writeGIF(char *filename)
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Write a GIF file to filename
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----------------------------------------------------------------------- */
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int FrameBuffer_writeGIF(FrameBuffer *f, ColorMap *c, char *filename) {
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file = fopen(filename,"wb");
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if (file == NULL) return -1;
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bufsize = (f->width*f->height*3)/2;
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buffer = (void *) malloc(bufsize);
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nbytes = FrameBuffer_makeGIF(f,c,buffer,bufsize);
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fwrite(buffer,nbytes,1,file);
added
removed
Examples/GIFPlot/Lib/gif.c
