A filter to convert IRIS images to Compuserve GIF format
Paul Haeberli
paul at manray.sgi.com
Tue Oct 3 17:59:52 AEST 1989
/*
* togif -
* Convert an IRIS image to GIF format. Converts b/w and
* color images to 8 bit per pixel GIF format. Color images
* are dithered with a 4 by 4 dither matrix. GIF image files
* may be uuencoded, and sent over the network.
*
* Paul Haeberli @ Silicon Graphics - 1989
*
* To compile use:
*
* cc -I/usr/include/gl togif.c -o togif -limage
*
*/
#include "image.h"
#define MAXXSIZE 4096
#define MAXCOLORS 256
short rbuf[MAXXSIZE];
short gbuf[MAXXSIZE];
short bbuf[MAXXSIZE];
short obuf[MAXXSIZE];
int rmap[MAXCOLORS];
int gmap[MAXCOLORS];
int bmap[MAXCOLORS];
int iscolor, currow;
IMAGE *iimage;
int getgifpix(x,y)
int x, y;
{
if(iscolor) {
if(currow!= y) {
getrow(iimage,rbuf,iimage->ysize-1-y,0);
getrow(iimage,gbuf,iimage->ysize-1-y,1);
getrow(iimage,bbuf,iimage->ysize-1-y,2);
ditherrow(rbuf,gbuf,bbuf,obuf,iimage->xsize,y);
currow = y;
}
return obuf[x];
} else {
if(currow!= y) {
getrow(iimage,rbuf,iimage->ysize-1-y,0);
currow = y;
}
return rbuf[x];
}
}
main( argc, argv )
int argc;
char *argv[];
{
FILE *of;
int xsize, ysize;
int i, bpp;
int r, g, b;
if(argc<2) {
fprintf(stderr,"usage: togif image.rgb image.gif\n");
exit(1);
}
iimage = iopen(argv[1],"r");
if(!iimage) {
fprintf(stderr,"togif: can't open input image [%s]\n",argv[1]);
exit(1);
}
xsize = iimage->xsize;
ysize = iimage->ysize;
if(iimage->zsize>=3)
iscolor = 1;
else
iscolor = 0;
of = fopen(argv[2],"w");
if(!of) {
fprintf(stderr,"togif: can't open out image [%s]\n",argv[2]);
exit(1);
}
if(iscolor) {
for(i=0; i<MAXCOLORS; i++) {
r = (i>>0)&0x7;
g = (i>>3)&0x7;
b = (i>>6)&0x3;
rmap[i] = (255*r)/7;
gmap[i] = (255*g)/7;
bmap[i] = (255*b)/3;
}
} else {
for(i=0; i<MAXCOLORS; i++) {
rmap[i] = i;
gmap[i] = i;
bmap[i] = i;
}
}
bpp = 8;
currow = -1;
GIFEncode(of,xsize,ysize,0,0,bpp,rmap,gmap,bmap,getgifpix);
exit(0);
}
/*
* dithering code follows
*
*
*/
#define XSIZE 4
#define YSIZE 4
#define TOTAL (XSIZE*YSIZE)
#define WRAPY(y) ((y)%YSIZE)
#define WRAPX(x) ((x)%XSIZE)
static short dithmat[YSIZE][XSIZE] = {
0, 8, 2, 10,
12, 4, 14, 6,
3, 11, 1, 9,
15, 7, 13, 5,
};
short **rtab;
short **gtab;
short **btab;
short **makedittab(levels,mult,add)
int levels, mult, add;
{
register int val;
register int nshades;
register int i, j, k;
register int matval, tabval;
short **tab;
nshades = XSIZE*YSIZE*(levels-1)+1;
tab = (short **)malloc(YSIZE*sizeof(short *));
for(j=0; j<YSIZE; j++) {
tab[j] = (short *)malloc(XSIZE*256*sizeof(short));
for(i=0; i<XSIZE; i++ ) {
matval = dithmat[i][j];
for(k=0; k<256; k++) {
val = (nshades*k)/255;
if(val==nshades)
val = nshades-1;
if((val%TOTAL)>matval)
tabval = (val/TOTAL)+1;
else
tabval = (val/TOTAL);
tabval *= mult;
tabval += add;
tab[j][256*i+k] = tabval;
}
}
}
return tab;
}
ditherrow(r,g,b,wp,n,y)
unsigned short *r, *g, *b;
short *wp;
int n, y;
{
short *rbase;
short *gbase;
short *bbase;
if(!rtab) {
rtab = makedittab(8,1,0);
gtab = makedittab(8,8,0);
btab = makedittab(4,64,0);
}
rbase = rtab[WRAPY(y)];
gbase = gtab[WRAPY(y)];
bbase = btab[WRAPY(y)];
while(n) {
if(n>=XSIZE) {
*wp++ = rbase[*r++ + 0] + gbase[*g++ + 0] + bbase[*b++ + 0];
*wp++ = rbase[*r++ + 256] + gbase[*g++ + 256] + bbase[*b++ + 256];
*wp++ = rbase[*r++ + 512] + gbase[*g++ + 512] + bbase[*b++ + 512];
*wp++ = rbase[*r++ + 768] + gbase[*g++ + 768] + bbase[*b++ + 768];
n -= XSIZE;
} else {
*wp++ = rbase[*r++] + gbase[*g++] + bbase[*b++];
rbase += 256;
gbase += 256;
bbase += 256;
n--;
}
}
}
/*
* SCARY GIF code follows . . . . sorry.
*
* Based on GIFENCOD by David Rowley <mgardi at watdscu.waterloo.edu>.A
* Lempel-Zim compression based on "compress".
*
*/
/*****************************************************************************
*
* GIFENCODE.C - GIF Image compression interface
*
* GIFEncode( FName, GHeight, GWidth, GInterlace, Background,
* BitsPerPixel, Red, Green, Blue, GetPixel )
*
*****************************************************************************/
typedef int (* ifunptr)();
#define TRUE 1
#define FALSE 0
int Width, Height;
int curx, cury;
long CountDown;
int Pass = 0;
int Interlace;
/*
* Bump the 'curx' and 'cury' to point to the next pixel
*/
BumpPixel()
{
curx++;
if( curx == Width ) {
curx = 0;
if( !Interlace ) {
cury++;
} else {
switch( Pass ) {
case 0:
cury += 8;
if( cury >= Height ) {
Pass++;
cury = 4;
}
break;
case 1:
cury += 8;
if( cury >= Height ) {
Pass++;
cury = 2;
}
break;
case 2:
cury += 4;
if( cury >= Height ) {
Pass++;
cury = 1;
}
break;
case 3:
cury += 2;
break;
}
}
}
}
/*
* Return the next pixel from the image
*/
GIFNextPixel( getpixel )
ifunptr getpixel;
{
int r;
if( CountDown == 0 )
return EOF;
CountDown--;
r = (*getpixel)( curx, cury );
BumpPixel();
return r;
}
/*
* public GIFEncode
*/
GIFEncode( fp, GWidth, GHeight, GInterlace, Background,
BitsPerPixel, Red, Green, Blue, GetPixel )
FILE *fp;
int GWidth, GHeight;
int GInterlace;
int Background;
int BitsPerPixel;
int Red[], Green[], Blue[];
ifunptr GetPixel;
{
int B;
int RWidth, RHeight;
int LeftOfs, TopOfs;
int Resolution;
int ColorMapSize;
int InitCodeSize;
int i;
Interlace = GInterlace;
ColorMapSize = 1 << BitsPerPixel;
RWidth = Width = GWidth;
RHeight = Height = GHeight;
LeftOfs = TopOfs = 0;
Resolution = BitsPerPixel;
CountDown = (long)Width * (long)Height;
Pass = 0;
if( BitsPerPixel <= 1 )
InitCodeSize = 2;
else
InitCodeSize = BitsPerPixel;
curx = cury = 0;
fwrite( "GIF87a", 1, 6, fp );
Putword( RWidth, fp );
Putword( RHeight, fp );
B = 0x80; /* Yes, there is a color map */
B |= (Resolution - 1) << 5;
B |= (BitsPerPixel - 1);
fputc( B, fp );
fputc( Background, fp );
fputc( 0, fp );
for( i=0; i<ColorMapSize; i++ ) {
fputc( Red[i], fp );
fputc( Green[i], fp );
fputc( Blue[i], fp );
}
fputc( ',', fp );
Putword( LeftOfs, fp );
Putword( TopOfs, fp );
Putword( Width, fp );
Putword( Height, fp );
if( Interlace )
fputc( 0x40, fp );
else
fputc( 0x00, fp );
fputc( InitCodeSize, fp );
compress( InitCodeSize+1, fp, GetPixel );
fputc( 0, fp );
fputc( ';', fp );
fclose( fp );
}
/*
* Write out a word to the GIF file
*/
Putword( w, fp )
int w;
FILE *fp;
{
fputc( w & 0xff, fp );
fputc( (w/256) & 0xff, fp );
}
/***************************************************************************
*
* GIFCOMPR.C - GIF Image compression routines
*
* Lempel-Ziv compression based on 'compress'. GIF modifications by
* David Rowley (mgardi at watdcsu.waterloo.edu)
*
***************************************************************************/
#define BITS 12
#define HSIZE 5003 /* 80% occupancy */
/*
* a code_int must be able to hold 2**BITS values of type int, and also -1
*/
typedef int code_int;
typedef long int count_int;
typedef unsigned char char_type;
/*
*
* 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)
*
*/
#include <ctype.h>
#define ARGVAL() (*++(*argv) || (--argc && *++argv))
int n_bits; /* number of bits/code */
int maxbits = BITS; /* user settable max # bits/code */
code_int maxcode; /* maximum code, given n_bits */
code_int maxmaxcode = (code_int)1 << BITS; /* should NEVER generate this code */
# define MAXCODE(n_bits) (((code_int) 1 << (n_bits)) - 1)
count_int htab [HSIZE];
unsigned short codetab [HSIZE];
#define HashTabOf(i) htab[i]
#define CodeTabOf(i) codetab[i]
code_int hsize = HSIZE; /* for dynamic table sizing */
count_int fsize;
/*
* To save much memory, we overlay the table used by compress() with those
* used by decompress(). The tab_prefix table is the same size and type
* as the codetab. The tab_suffix table needs 2**BITS characters. We
* get this from the beginning of htab. The output stack uses the rest
* of htab, and contains characters. There is plenty of room for any
* possible stack (stack used to be 8000 characters).
*/
#define tab_prefixof(i) CodeTabOf(i)
#define tab_suffixof(i) ((char_type *)(htab))[i]
#define de_stack ((char_type *)&tab_suffixof((code_int)1<<BITS))
code_int free_ent = 0; /* first unused entry */
int exit_stat = 0;
/*
* block compression parameters -- after all codes are used up,
* and compression rate changes, start over.
*/
int clear_flg = 0;
int offset;
long int in_count = 1; /* length of input */
long int out_count = 0; /* # of codes output (for debugging) */
/*
* compress stdin to stdout
*
* 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.
*/
int g_init_bits;
FILE *g_outfile;
int ClearCode;
int EOFCode;
compress( init_bits, outfile, ReadValue )
int init_bits;
FILE *outfile;
ifunptr ReadValue;
{
register long fcode;
register code_int i = 0;
register int c;
register code_int ent;
register code_int disp;
register code_int hsize_reg;
register int hshift;
/*
* Set up the globals: g_init_bits - initial number of bits
* g_outfile - pointer to output file
*/
g_init_bits = init_bits;
g_outfile = outfile;
/*
* Set up the necessary values
*/
offset = 0;
out_count = 0;
clear_flg = 0;
in_count = 1;
maxcode = MAXCODE(n_bits = g_init_bits);
ClearCode = (1 << (init_bits - 1));
EOFCode = ClearCode + 1;
free_ent = ClearCode + 2;
char_init();
ent = GIFNextPixel( ReadValue );
hshift = 0;
for ( fcode = (long) hsize; fcode < 65536L; fcode *= 2L )
hshift++;
hshift = 8 - hshift; /* set hash code range bound */
hsize_reg = hsize;
cl_hash( (count_int) hsize_reg); /* clear hash table */
output( (code_int)ClearCode );
while ( (c = GIFNextPixel( ReadValue )) != EOF ) {
in_count++;
fcode = (long) (((long) c << maxbits) + ent);
/* i = (((code_int)c << hshift) ~ ent); /* xor hashing */
i = (((code_int)c << hshift) ^ ent); /* xor hashing */
if ( HashTabOf (i) == fcode ) {
ent = CodeTabOf (i);
continue;
} else if ( (long)HashTabOf (i) < 0 ) /* empty slot */
goto nomatch;
disp = hsize_reg - i; /* secondary hash (after G. Knott) */
if ( i == 0 )
disp = 1;
probe:
if ( (i -= disp) < 0 )
i += hsize_reg;
if ( HashTabOf (i) == fcode ) {
ent = CodeTabOf (i);
continue;
}
if ( (long)HashTabOf (i) > 0 )
goto probe;
nomatch:
output ( (code_int) ent );
out_count++;
ent = c;
if ( free_ent < maxmaxcode ) {
CodeTabOf (i) = free_ent++; /* code -> hashtable */
HashTabOf (i) = fcode;
} else
cl_block();
}
/*
* Put out the final code.
*/
output( (code_int)ent );
out_count++;
output( (code_int) EOFCode );
return;
}
/*****************************************************************
* TAG( output )
*
* Output the given code.
* Inputs:
* code: A n_bits-bit integer. If == -1, then EOF. This assumes
* that n_bits =< (long)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.
*/
unsigned long cur_accum = 0;
int cur_bits = 0;
unsigned long masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
0x001F, 0x003F, 0x007F, 0x00FF,
0x01FF, 0x03FF, 0x07FF, 0x0FFF,
0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };
output( code )
code_int code;
{
cur_accum &= masks[ cur_bits ];
if( cur_bits > 0 )
cur_accum |= ((long)code << cur_bits);
else
cur_accum = code;
cur_bits += n_bits;
while( cur_bits >= 8 ) {
char_out( (unsigned int)(cur_accum & 0xff) );
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 = 0;
} 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( (unsigned int)(cur_accum & 0xff) );
cur_accum >>= 8;
cur_bits -= 8;
}
flush_char();
fflush( g_outfile );
if( ferror( g_outfile ) )
writeerr();
}
}
/*
* Clear out the hash table
*/
cl_block () /* table clear for block compress */
{
cl_hash ( (count_int) hsize );
free_ent = ClearCode + 2;
clear_flg = 1;
output( (code_int)ClearCode );
}
cl_hash(hsize) /* reset code table */
register count_int hsize;
{
register count_int *htab_p = htab+hsize;
register long i;
register long m1 = -1;
i = hsize - 16;
do { /* might use Sys V memset(3) here */
*(htab_p-16) = m1;
*(htab_p-15) = m1;
*(htab_p-14) = m1;
*(htab_p-13) = m1;
*(htab_p-12) = m1;
*(htab_p-11) = m1;
*(htab_p-10) = m1;
*(htab_p-9) = m1;
*(htab_p-8) = m1;
*(htab_p-7) = m1;
*(htab_p-6) = m1;
*(htab_p-5) = m1;
*(htab_p-4) = m1;
*(htab_p-3) = m1;
*(htab_p-2) = m1;
*(htab_p-1) = m1;
htab_p -= 16;
} while ((i -= 16) >= 0);
for ( i += 16; i > 0; i-- )
*--htab_p = m1;
}
writeerr()
{
printf( "error writing output file\n" );
exit(1);
}
/******************************************************************************
*
* GIF Specific routines
*
******************************************************************************/
/*
* Number of characters so far in this 'packet'
*/
int a_count;
/*
* Set up the 'byte output' routine
*/
char_init()
{
a_count = 0;
}
/*
* Define the storage for the packet accumulator
*/
char accum[ 256 ];
/*
* Add a character to the end of the current packet, and if it is 254
* characters, flush the packet to disk.
*/
char_out( c )
int c;
{
accum[ a_count++ ] = c;
if( a_count >= 254 )
flush_char();
}
/*
* Flush the packet to disk, and reset the accumulator
*/
flush_char()
{
if( a_count > 0 ) {
fputc( a_count, g_outfile );
fwrite( accum, 1, a_count, g_outfile );
a_count = 0;
}
}
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