Category : C Source Code
Archive : ENCODER.ZIP
Filename : GIFENCOD.C
Output of file : GIFENCOD.C contained in archive : ENCODER.ZIP
/*****************************************************************************
*
* GIFENCODE.C - GIF Image compression interface
*
* GIFEncode( FName, GHeight, GWidth, GInterlace, Background,
* BitsPerPixel, Red, Green, Blue, GetPixel )
*
*****************************************************************************/
#include
/*
* Pointer to function returning an int
*/
typedef int (* ifunptr)();
#define TRUE 1
#define FALSE 0
static int Width, Height;
static int curx, cury;
static long CountDown;
static int Pass = 0;
static int Interlace;
/*
* Bump the 'curx' and 'cury' to point to the next pixel
*/
static
BumpPixel()
{
/*
* Bump the current X position
*/
curx++;
/*
* If we are at the end of a scan line, set curx back to the beginning
* If we are interlaced, bump the cury to the appropriate spot,
* otherwise, just increment it.
*/
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( FName, GWidth, GHeight, GInterlace, Background,
BitsPerPixel, Red, Green, Blue, GetPixel )
char *FName;
int GWidth, GHeight;
int GInterlace;
int Background;
int BitsPerPixel;
int Red[], Green[], Blue[];
ifunptr GetPixel;
{
FILE *fp;
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;
/*
* Calculate number of bits we are expecting
*/
CountDown = (long)Width * (long)Height;
/*
* Indicate which pass we are on (if interlace)
*/
Pass = 0;
/*
* The initial code size
*/
if( BitsPerPixel <= 1 )
InitCodeSize = 2;
else
InitCodeSize = BitsPerPixel;
/*
* Set up the current x and y position
*/
curx = cury = 0;
/*
* Open the GIF file for binary write
*/
fp = fopen( FName, "wb" );
if( fp == (FILE *)0 ) {
printf( "error: could not open output file\n" );
exit(1);
}
/*
* Write the Magic header
*/
fwrite( "GIF87a", 1, 6, fp );
/*
* Write out the screen width and height
*/
Putword( RWidth, fp );
Putword( RHeight, fp );
/*
* Indicate that there is a global colour map
*/
B = 0x80; /* Yes, there is a color map */
/*
* OR in the resolution
*/
B |= (Resolution - 1) << 5;
/*
* OR in the Bits per Pixel
*/
B |= (BitsPerPixel - 1);
/*
* Write it out
*/
fputc( B, fp );
/*
* Write out the Background colour
*/
fputc( Background, fp );
/*
* Byte of 0's (future expansion)
*/
fputc( 0, fp );
/*
* Write out the Global Colour Map
*/
for( i=0; i
fputc( Green[i], fp );
fputc( Blue[i], fp );
}
/*
* Write an Image separator
*/
fputc( ',', fp );
/*
* Write the Image header
*/
Putword( LeftOfs, fp );
Putword( TopOfs, fp );
Putword( Width, fp );
Putword( Height, fp );
/*
* Write out whether or not the image is interlaced
*/
if( Interlace )
fputc( 0x40, fp );
else
fputc( 0x00, fp );
/*
* Write out the initial code size
*/
fputc( InitCodeSize, fp );
/*
* Go and actually compress the data
*/
compress( InitCodeSize+1, fp, GetPixel );
/*
* Write out a Zero-length packet (to end the series)
*/
fputc( 0, fp );
/*
* Write the GIF file terminator
*/
fputc( ';', fp );
/*
* And close the file
*/
fclose( fp );
}
/*
* Write out a word to the GIF file
*/
static
Putword( w, fp )
int w;
FILE *fp;
{
fputc( w & 0xff, fp );
fputc( (w / 256) & 0xff, fp );
}
Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/