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/*****************************************************************************
*
* GIFENCODE.C - GIF Image compression interface
*
* GIFEncode( FName, GHeight, GWidth, GInterlace, Background,
* BitsPerPixel, Red, Green, Blue, GetPixel )
*
* Modified for use with RLE interface, Spencer W. Thomas, June, 1990.
* (replaced fopen with rle_open_f).
*
*****************************************************************************/
#include <stdio.h>
#include <rle.h>
#include "rletogif.h"
#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;
short int Red[], Green[], Blue[];
ifunptr GetPixel;
{
FILE *fp;
int B;
int RWidth, RHeight;
int LeftOfs, TopOfs;
int Resolution;
int ColorMapSize;
int InitCodeSize;
int i;
/* doesn't support interlace yet */
if (GInterlace) error("no support for interlace yet");
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 = rle_open_f( MY_NAME, FName, "w" );
/*
* 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<ColorMapSize; i++ ) {
fputc( Red[i]>>8, fp );
fputc( Green[i]>>8, fp );
fputc( Blue[i]>>8, 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
*/
compgif( 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
*/
Putword( w, fp )
int w;
FILE *fp;
{
fputc( w & 0xff, fp );
fputc( (w >> 8) & 0xff, fp );
}
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