quantize.h

/*****************************************************************************
 *   "Gif-Lib" - Yet another gif library.
 *
 * Written by:  Gershon Elber            IBM PC Ver 0.1,    Jun. 1989
 ******************************************************************************
 * Module to quatize high resolution image into lower one. You may want to
 * peek into the following article this code is based on:
 * "Color Image Quantization for frame buffer Display", by Paul Heckbert
 * SIGGRAPH 1982 page 297-307.
 ******************************************************************************
 * History:
 * 5 Jan 90 - Version 1.0 by Gershon Elber.
 *****************************************************************************/

#include <stdlib.h>
#include <stdio.h>

#define GIF_ERROR   0
#define GIF_OK      1

typedef unsigned char GifPixelType;
typedef unsigned char GifByteType;

typedef struct GifColorType {
    GifByteType Red, Green, Blue;
} GifColorType;

typedef struct QuantizedColorType {
    GifByteType RGB[3];
    GifByteType NewColorIndex;
    long Count;
    struct QuantizedColorType *Pnext;
} QuantizedColorType;

typedef struct NewColorMapType {
    GifByteType RGBMin[3], RGBWidth[3];
    unsigned int NumEntries; /* # of QuantizedColorType in linked list below */
    unsigned long Count; /* Total number of pixels in all the entries */
    QuantizedColorType *QuantizedColors;
} NewColorMapType;

/******************************************************************************
 * Quantize high resolution image into lower one. Input image consists of a
 * 2D array for each of the RGB colors with size Width by Height. There is no
 * Color map for the input. Output is a quantized image with 2D array of
 * indexes into the output color map.
 *   Note input image can be 24 bits at the most (8 for red/green/blue) and
 * the output has 256 colors at the most (256 entries in the color map.).
 * ColorMapSize specifies size of color map up to 256 and will be updated to
 * real size before returning.
 *   Also non of the parameter are allocated by this routine.
 *   This function returns GIF_OK if succesfull, GIF_ERROR otherwise.
 ******************************************************************************/
int
QuantizeBuffer(unsigned int Width,
               unsigned int Height,
               int *ColorMapSize,
               GifByteType * RedInput,
               GifByteType * GreenInput,
               GifByteType * BlueInput,
               GifByteType * OutputBuffer,
               GifColorType * OutputColorMap);