Category : C Source Code
Archive   : FRAC151S.ZIP
Filename : GIFVIEW.C

 
Output of file : GIFVIEW.C contained in archive : FRAC151S.ZIP

/*
*
* 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
#include
#include
#include "fractint.h"

/* routines in this module */

int gifview(void);
int get_byte(void); /* used only locally and by decoder.c */

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 MAP_name[];
extern int mapset;

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 */
}

extern unsigned char dacbox[256][3]; /* Video-DAC (filled in by SETVIDEO) */
extern int reallyega; /* "really-an-ega" flag */
extern int paletteVGA[16]; /* VGA Palette-to-DAC registers */
extern unsigned char decoderline[2049]; /* write-line routines use this */

/* Main entry decoder */
int gifview()
{
unsigned numcolors;
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++)
{
if ((buffer[i] = (unsigned char)get_byte ()) < 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++)
{
if (numcolors == 16 && !reallyega) /* straight copy or indirect via palette? */
k = paletteVGA[i];
else
k = i;
for (j = 0; j < 3; j++) {
if ((buffer[j] = (unsigned char)get_byte()) < 0)
{
close_file();
return(-1);
}
if (dacbox[0][0] != 255) /* (only if we really have a DAC) */
if(!display3d || (glassestype != 1 && glassestype != 2))
dacbox[k][j] = buffer[j] >> 2;
}
}
/* don't read if glasses */
if (display3d && mapset && glassestype!=1 && glassestype != 2)
{
ValidateLuts(MAP_name); /* read the palette file */
if (dotmode != 11)
spindac(0,1); /* load it, but don't spin */
}
if (dacbox[0][0] != 255 && dotmode != 11)
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++)
{
if ((buffer[i] = (unsigned char)get_byte ()) < 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;

/* Setup the color palette for the image */

if (calc_status == 1) /* should never be so, but make sure */
calc_status = 0;
status = timer(1,NULL,width); /* call decoder(width) via timer */
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;
}