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GIFVIEW.C
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1992-01-03
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6KB
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251 lines
/*
*
* This GIF decoder is designed for use with Bert Tyler's FRACTINT
* program. It should be noted that the "FRACTINT" program only decodes
* GIF files FRACTINT creates, so this decoder code lacks full generality
* in the following respects: supports single image, non-interlaced GIF
* files with no local color maps and no extension blocks.
*
* GIF and 'Graphics Interchange Format' are trademarks (tm) of
* Compuserve, Incorporated, an H&R Block Company.
*
* Tim Wegner
*/
#include <stdio.h>
#include <string.h>
#include <dos.h>
#include "fractint.h"
/* routines in this module */
int gifview(void);
int get_byte(void); /* used only locally and by decoder.c */
int get_bytes(char *,int); /* used only by decoder.c *mg*/
static void close_file(void);
#define MAXCOLORS 256
extern int timer(int timertype,int(*subrtn)(),...);
extern int rowcount; /* row counter for screen */
extern char readname[]; /* file name */
static FILE *fpin = NULL; /* FILE pointer */
unsigned int height;
extern char busy;
unsigned numcolors;
extern char MAP_name[];
extern int mapset;
extern int colorstate; /* comments in cmdfiles */
extern int glassestype;
extern int display3d;
extern int dotmode; /* so we can detect disk-video */
extern int calc_status;
extern long calctime;
extern long timer_interval;
extern int pot16bit; /* 16 bit values for continuous potential */
int bad_code_count = 0; /* needed by decoder module */
int get_byte()
{
return (getc(fpin)); /* EOF is -1, as desired */
}
int get_bytes(char *where,int how_many)
{
return (fread(where,1,how_many,fpin)); /* EOF is -1, as desired */
}
extern unsigned char dacbox[256][3]; /* Video-DAC (filled in by SETVIDEO) */
extern unsigned char decoderline[2049]; /* write-line routines use this */
/* Main entry decoder */
int gifview()
{
unsigned char buffer[16];
unsigned width, finished;
char temp1[81];
int status;
int i, j, k, planes;
status = 0;
/* initialize the row count for write-lines */
rowcount = 0;
/* zero out the full write-line */
for (width = 0; width < 2049; width++) decoderline[width] = 0;
/* Open the file */
strcpy(temp1,readname);
if (strchr(temp1,'.') == NULL) {
strcat(temp1,DEFAULTFRACTALTYPE);
if ((fpin = fopen(temp1,"rb")) != NULL) {
fclose(fpin);
}
else {
strcpy(temp1,readname);
strcat(temp1,ALTERNATEFRACTALTYPE);
}
}
if ((fpin = fopen(temp1, "rb")) == NULL)
return (-1);
/* Get the screen description */
for (i = 0; i < 13; i++)
{
int tmp;
buffer[i] = tmp = get_byte();
if (tmp < 0)
{
close_file();
return(-1);
}
}
if(strncmp(buffer,"GIF87a",3) || /* use updated GIF specs */
buffer[3] < '0' || buffer[3] > '9' ||
buffer[4] < '0' || buffer[4] > '9' ||
buffer[5] < 'A' || buffer[5] > 'z' )
{
close_file();
return(-1);
}
planes = (buffer[10] & 0x0F) + 1;
if((buffer[10] & 0x80)==0) /* color map (better be!) */
{
close_file();
return(-1);
}
numcolors = 1 << planes;
for (i = 0; i < numcolors; i++)
{
for (j = 0; j < 3; j++) {
if ((k = get_byte()) < 0)
{
close_file();
return(-1);
}
if(!display3d || (glassestype != 1 && glassestype != 2))
dacbox[i][j] = k >> 2;
}
}
colorstate = 1; /* colors aren't default and not a known .map file */
/* don't read if glasses */
if (display3d && mapset && glassestype!=1 && glassestype != 2)
{
ValidateLuts(MAP_name); /* read the palette file */
spindac(0,1); /* load it, but don't spin */
}
if (dacbox[0][0] != 255)
spindac(0,1); /* update the DAC */
if (dotmode == 11) /* disk-video */
dvid_status(1,"...restoring...");
/* Now display one or more GIF objects */
finished = 0;
while (!finished)
{
switch (get_byte())
{
case ';':
/* End of the GIF dataset */
finished = 1;
status = 0;
break;
case '!': /* GIF Extension Block */
get_byte(); /* read (and ignore) the ID */
while ((i = get_byte()) > 0) /* get the data length */
for (j = 0; j < i; j++)
get_byte(); /* flush the data */
break;
case ',':
/*
* Start of an image object. Read the image description.
*/
for (i = 0; i < 9; i++)
{
int tmp;
buffer[i] = tmp = get_byte();
if (tmp < 0)
{
status = -1;
break;
}
}
if(status < 0)
{
finished = 1;
break;
}
width = buffer[4] | (buffer[5] << 8);
if (pot16bit) width >>= 1;
height = buffer[6] | (buffer[7] << 8);
/* Skip local color palette */
if((buffer[8] & 0x80)==0x80) { /* local map? */
int numcolors; /* make this local */
planes = (buffer[8] & 0x0F) + 1;
numcolors = 1 << planes;
/* skip local map */
for (i = 0; i < numcolors; i++) {
for (j = 0; j < 3; j++) {
if ((k = get_byte()) < 0) {
close_file();
return(-1);
}
}
}
}
if (calc_status == 1) /* should never be so, but make sure */
calc_status = 0;
busy = 1; /* for slideshow CALCWAIT */
status = timer(1,NULL,width); /* call decoder(width) via timer */
busy = 0; /* for slideshow CALCWAIT */
if (calc_status == 1) /* e.g., set by line3d */
{
calctime = timer_interval; /* note how long it took */
if (keypressed() != 0)
calc_status = 3; /* interrupted, not resumable */
else
calc_status = 4; /* complete */
}
finished = 1;
break;
default:
status = -1;
finished = 1;
break;
}
}
close_file();
if (dotmode == 11) { /* disk-video */
dvid_status(0,"Restore completed");
dvid_status(1,"");
}
return(status);
}
static void close_file()
{
fclose(fpin);
fpin = NULL;
}