gifencod.c File Reference

#include <stdio.h>
#include "rle.h"
#include "rletogif.h"

Include dependency graph for gifencod.c:

Go to the source code of this file.

Macros
#define	TRUE   1
#define	FALSE   0

Functions
static void	BumpPixel ()
static void	Putword (int w, FILE *fp)
int	GIFNextPixel (ifunptr getpixel)
void	GIFEncode (char *FName, int GWidth, int GHeight, int GInterlace, int Background, int BitsPerPixel, Red, Green, Blue, ifunptr GetPixel)

Variables
static int	Width
static int	Height
static int	curx
static int	cury
static long	CountDown
static int	Pass = 0
static int	Interlace

Macro Definition Documentation

#define FALSE   0

Definition at line 19 of file gifencod.c.

#define TRUE   1

Definition at line 18 of file gifencod.c.

Function Documentation

static void BumpPixel ( )

static

Definition at line 33 of file gifencod.c.

References curx, cury, Height, Interlace, Pass, and Width.

{
    /*
     * 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;
            }
        }
    }
}

void GIFEncode	(	char *	FName,
		int	GWidth,
		int	GHeight,
		int	GInterlace,
		int	Background,
		int	BitsPerPixel,
		Red	,
		Green	,
		Blue	,
		ifunptr	GetPixel
	)

Definition at line 122 of file gifencod.c.

{
    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 );
    
}

int GIFNextPixel

(

ifunptr

getpixel

)

Definition at line 102 of file gifencod.c.

{
    int r;

    if( CountDown == 0 )
        return EOF;

    CountDown--;

    r = ( * getpixel )( curx, cury );

    BumpPixel();

    return r;
}

static void Putword ( int  w, FILE *  fp  )

static

Definition at line 89 of file gifencod.c.

{
    fputc( w & 0xff, fp );
    fputc( (w >> 8) & 0xff, fp );
}

Variable Documentation

long CountDown

static

Definition at line 23 of file gifencod.c.

int curx

static

Definition at line 22 of file gifencod.c.

Referenced by BumpPixel().

int cury

static

Definition at line 22 of file gifencod.c.

Referenced by BumpPixel().

int Height

static

Definition at line 21 of file gifencod.c.

Referenced by BumpPixel().

int Interlace

static

Definition at line 25 of file gifencod.c.

Referenced by BumpPixel().

int Pass = 0

static

Definition at line 24 of file gifencod.c.

Referenced by BumpPixel().

int Width

static

Definition at line 21 of file gifencod.c.

Referenced by BumpPixel().