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GIF.C
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C/C++ Source or Header
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1991-05-07
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8KB
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242 lines
/*****************************************************************************
*
* gif.c
*
* from DKBTrace (c) 1990 David Buck
*
* Gif-format file reader.
*
* NOTE: Portions of this module were written by Steve Bennett and are used
* here with his permission.
*
* This software is freely distributable. The source and/or object code may be
* copied or uploaded to communications services so long as this notice remains
* at the top of each file. If any changes are made to the program, you must
* clearly indicate in the documentation and in the programs startup message
* who it was who made the changes. The documentation should also describe what
* those changes were. This software may not be included in whole or in
* part into any commercial package without the express written consent of the
* author. It may, however, be included in other public domain or freely
* distributed software so long as the proper credit for the software is given.
*
* This software is provided as is without any guarantees or warranty. Although
* the author has attempted to find and correct any bugs in the software, he
* is not responsible for any damage caused by the use of the software. The
* author is under no obligation to provide service, corrections, or upgrades
* to this package.
*
* Despite all the legal stuff above, if you do find bugs, I would like to hear
* about them. Also, if you have any comments or questions, you may contact me
* at the following address:
*
* David Buck
* 22C Sonnet Cres.
* Nepean Ontario
* Canada, K2H 8W7
*
* I can also be reached on the following bulleton boards:
*
* OMX (613) 731-3419
* Mystic (613) 596-4249 or (613) 596-4772
*
* Fidonet: 1:163/109.9
* Internet: dbuck@ccs.carleton.ca
* The "You Can Call Me RAY" BBS (708) 358-5611
*
* IBM Port by Aaron A. Collins. Aaron may be reached on the following BBS'es:
*
* The "You Can Call Me RAY" BBS (708) 358-5611
* The Information Exchange BBS (708) 945-5575
*
*****************************************************************************/
/*
The following routines were borrowed freely from FRACTINT, and represent
a generalized GIF file decoder. This seems the best, most universal format
for reading in Bitmapped images. GIF is a Copyright of Compuserve, Inc.
Swiped and converted to entirely "C" coded routines by AAC for the most
in future portability!
*/
#include "frame.h"
#include "dkbproto.h"
static IMAGE *Current_Image;
static int Bitmap_Line;
static FILE *Bit_File;
unsigned char *decoderline /* [2049] */ ; /* write-line routines use this */
static IMAGE_COLOUR *gif_colour_map;
static int colourmap_size;
int out_line (pixels, linelen)
unsigned char *pixels;
int linelen;
{
register int x;
register unsigned char *line;
line = Current_Image->data.map_lines[Bitmap_Line++];
for (x = 0; x < linelen; x++) {
if ((int)(*pixels) > Current_Image->Colour_Map_Size) {
fprintf (stderr, "Error - GIF Image Map Colour out of range\n");
exit(1);
}
line[x] = *pixels;
pixels++;
}
return (0);
}
#define READ_ERROR -1
int get_byte() /* get byte from file, return the next byte or an error */
{
register int byte;
if ((byte = getc(Bit_File)) != EOF)
return (byte);
else {
fprintf (stderr, "Premature End Of File reading GIF image\n");
exit (1);
}
return (0); /* Keep the compiler happy */
}
/* Main GIF file decoder. */
void Read_Gif_Image(Image, filename)
IMAGE *Image;
char *filename;
{
register int i, j, status;
unsigned finished, planes;
unsigned char buffer[16];
status = 0;
Current_Image = Image;
if ((Bit_File = Locate_File(filename, "rb")) == NULL) {
fprintf (stderr, "Cannot open GIF file %s\n", filename);
exit(1);
}
/* zero out the full write-line */
if ((decoderline = (unsigned char *) malloc (2049)) == NULL) {
fprintf (stderr, "Cannot allocate space for GIF decoder line\n");
fclose (Bit_File);
exit (1);
}
for (i = 0; i < 2049; i++)
decoderline[i] = (unsigned char) 0;
/* Get the screen description */
for (i = 0; i < 13; i++)
buffer[i] = (unsigned char)get_byte();
if (strncmp((char *) buffer,"GIF",3) || /* use updated GIF specs */
buffer[3] < '0' || buffer[3] > '9' ||
buffer[4] < '0' || buffer[4] > '9' ||
buffer[5] < 'A' || buffer[5] > 'z' ) {
fprintf (stderr, "Invalid GIF file format: %s\n", filename);
fclose(Bit_File);
exit (1);
}
planes = ((unsigned)buffer[10] & 0x0F) + 1;
colourmap_size = (int)(1 << planes);
if ((gif_colour_map = (IMAGE_COLOUR *)
malloc (colourmap_size * sizeof (IMAGE_COLOUR))) == NULL) {
fprintf (stderr, "Cannot allocate GIF Colour Map\n");
fclose (Bit_File);
exit (1);
}
if ((buffer[10] & 0x80) == 0) { /* color map (better be!) */
fprintf (stderr, "Invalid GIF file format: %s\n", filename);
fclose(Bit_File);
exit (1);
}
for (i = 0; i < colourmap_size ; i++) {
gif_colour_map[i].Red = (unsigned char)get_byte();
gif_colour_map[i].Green = (unsigned char)get_byte();
gif_colour_map[i].Blue = (unsigned char)get_byte();
gif_colour_map[i].Alpha = 0;
}
/* Now display one or more GIF objects */
finished = FALSE;
while (!finished) {
switch (get_byte()) {
case ';': /* End of the GIF dataset */
finished = TRUE;
status = 0;
break;
case '!': /* GIF Extension Block */
get_byte(); /* read (and ignore) the ID */
while ((i = get_byte()) > 0) /* get data len*/
for (j = 0; j < i; j++)
get_byte(); /* flush data */
break;
case ',': /* Start of image object. get description */
for (i = 0; i < 9; i++) {
if ((j = get_byte()) < 0) { /* EOF test (?) */
status = -1;
break;
}
buffer[i] = (unsigned char) j;
}
if (status < 0) {
finished = TRUE;
break;
}
Image->iwidth = buffer[4] | (buffer[5] << 8);
Image->iheight = buffer[6] | (buffer[7] << 8);
Image->width = (DBL) Image->iwidth;
Image->height = (DBL) Image->iheight;
Bitmap_Line = 0;
Image->Colour_Map_Size = colourmap_size;
Image->Colour_Map = gif_colour_map;
if ((Image->data.map_lines = (unsigned char **)
malloc(Image->iheight * sizeof (unsigned char *)))==NULL) {
fprintf (stderr, "Cannot allocate memory for picture\n");
exit(1);
}
for (i = 0 ; i < Image->iheight ; i++) {
if ((Image->data.map_lines[i] = (unsigned char *) malloc(Image->iwidth))==NULL) {
fprintf (stderr, "Cannot allocate memory for picture\n");
exit(1);
}
}
/* Setup the color palette for the image */
status = decoder ((short) Image->iwidth); /*put bytes in Buf*/
finished = TRUE;
break;
default:
status = -1;
finished = TRUE;
break;
}
}
free (decoderline);
fclose(Bit_File);
}