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G/LIB/QUANTIZE.C
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335
G/LIB/QUANTIZE.C
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/*****************************************************************************
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* "Gif-Lib" - Yet another gif library. *
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* *
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* Written by: Gershon Elber IBM PC Ver 0.1, Jun. 1989 *
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******************************************************************************
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* Module to quatize high resolution image into lower one. You may want to *
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* peek into the following article this code is based on: *
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* "Color Image Quantization for frame buffer Display", by Paul Heckbert *
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* SIGGRAPH 1982 page 297-307. *
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******************************************************************************
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* History: *
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* 5 Jan 90 - Version 1.0 by Gershon Elber. *
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*****************************************************************************/
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#ifdef __MSDOS__
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#include <dos.h>
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#include <alloc.h>
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#include <stdlib.h>
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#include <graphics.h>
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#endif /* __MSDOS__ */
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#include <stdio.h>
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#include "gif_lib.h"
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#define PROGRAM_NAME "GIF_LIBRARY"
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#define ABS(x) ((x) > 0 ? (x) : (-(x)))
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/* The colors are stripped to 5 bits per primary color if non MSDOS system */
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/* or to 4 (not enough memory...) if MSDOS as first step. */
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#ifdef __MSDOS__
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#define COLOR_ARRAY_SIZE 4096
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#define BITS_PER_PRIM_COLOR 4
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#define MAX_PRIM_COLOR 0x0f
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#else
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#define COLOR_ARRAY_SIZE 32768
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#define BITS_PER_PRIM_COLOR 5
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#define MAX_PRIM_COLOR 0x1f
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#endif /* __MSDOS__ */
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extern int _GifError;
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#ifdef SYSV
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static char *VersionStr =
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"Gif library module,\t\tGershon Elber\n\
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(C) Copyright 1989 Gershon Elber, Non commercial use only.\n";
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#else
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static char *VersionStr =
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PROGRAM_NAME
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" IBMPC "
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GIF_LIB_VERSION
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" Gershon Elber, "
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__DATE__ ", " __TIME__ "\n"
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"(C) Copyright 1989 Gershon Elber, Non commercial use only.\n";
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#endif /* SYSV */
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static int SortRGBAxis;
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typedef struct QuantizedColorType {
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GifByteType RGB[3];
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GifByteType NewColorIndex;
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long Count;
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struct QuantizedColorType *Pnext;
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} QuantizedColorType;
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typedef struct NewColorMapType {
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GifByteType RGBMin[3], RGBWidth[3];
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unsigned int NumEntries;/* # of QuantizedColorType in linked list below. */
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long Count; /* Total number of pixels in all the entries. */
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QuantizedColorType *QuantizedColors;
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} NewColorMapType;
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static int SubdivColorMap(NewColorMapType *NewColorSubdiv,
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unsigned int ColorMapSize,
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unsigned int *NewColorMapSize);
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#ifdef __MSDOS__
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static int SortCmpRtn(const VoidPtr Entry1, const VoidPtr Entry2);
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#else
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static int SortCmpRtn(VoidPtr Entry1, VoidPtr Entry2);
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#endif /* __MSDOS__ */
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/******************************************************************************
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* Quantize high resolution image into lower one. Input image consists of a *
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* 2D array for each of the RGB colors with size Width by Height. There is no *
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* Color map for the input. Output is a quantized image with 2D array of *
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* indexes into the output color map. *
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* Note input image can be 24 bits at the most (8 for red/green/blue) and *
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* the output has 256 colors at the most (256 entries in the color map.). *
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* ColorMapSize specifies size of color map up to 256 and will be updated to *
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* real size before returning. *
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* Also non of the parameter are allocated by this routine. *
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* This function returns GIF_OK if succesfull, GIF_ERROR otherwise. *
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******************************************************************************/
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int QuantizeBuffer(unsigned int Width, unsigned int Height, int *ColorMapSize,
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GifByteType *RedInput, GifByteType *GreenInput, GifByteType *BlueInput,
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GifByteType *OutputBuffer, GifColorType *OutputColorMap)
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{
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unsigned int i, j, Index, NewColorMapSize, NumOfEntries, MaxRGBError[3];
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long Red, Green, Blue;
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NewColorMapType NewColorSubdiv[256];
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QuantizedColorType *ColorArrayEntries, *QuantizedColor;
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if ((ColorArrayEntries = (QuantizedColorType *)
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malloc(sizeof(QuantizedColorType) * COLOR_ARRAY_SIZE)) == NULL) {
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_GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
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return GIF_ERROR;
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}
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for (i = 0; i < COLOR_ARRAY_SIZE; i++) {
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ColorArrayEntries[i].RGB[0]= i >> (2 * BITS_PER_PRIM_COLOR);
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ColorArrayEntries[i].RGB[1] = (i >> BITS_PER_PRIM_COLOR) &
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MAX_PRIM_COLOR;
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ColorArrayEntries[i].RGB[2] = i & MAX_PRIM_COLOR;
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ColorArrayEntries[i].Count = 0;
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}
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/* Sample the colors and their distribution: */
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for (i = 0; i < Width * Height; i++) {
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Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR))
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<< (2 * BITS_PER_PRIM_COLOR)) +
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((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR))
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<< BITS_PER_PRIM_COLOR) +
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(BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR));
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ColorArrayEntries[Index].Count++;
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}
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/* Put all the colors in the first entry of the color map, and call the */
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/* recursive subdivision process. */
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for (i = 0; i < 256; i++) {
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NewColorSubdiv[i].QuantizedColors = NULL;
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NewColorSubdiv[i].Count = NewColorSubdiv[i].NumEntries = 0;
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for (j = 0; j < 3; j++) {
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NewColorSubdiv[i].RGBMin[j] = 0;
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NewColorSubdiv[i].RGBWidth[j] = 255;
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}
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}
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/* Find the non empty entries in the color table and chain them: */
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for (i = 0; i < COLOR_ARRAY_SIZE; i++)
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if (ColorArrayEntries[i].Count > 0) break;
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QuantizedColor = NewColorSubdiv[0].QuantizedColors = &ColorArrayEntries[i];
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NumOfEntries = 1;
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while (++i < COLOR_ARRAY_SIZE)
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if (ColorArrayEntries[i].Count > 0) {
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QuantizedColor -> Pnext = &ColorArrayEntries[i];
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QuantizedColor = &ColorArrayEntries[i];
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NumOfEntries++;
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}
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QuantizedColor -> Pnext = NULL;
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NewColorSubdiv[0].NumEntries = NumOfEntries;/* Different sampled colors. */
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NewColorSubdiv[0].Count = ((long) Width) * Height; /* Pixels. */
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NewColorMapSize = 1;
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if (SubdivColorMap(NewColorSubdiv, *ColorMapSize, &NewColorMapSize) !=
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GIF_OK) {
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free((char *) ColorArrayEntries);
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return GIF_ERROR;
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}
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if (NewColorMapSize < *ColorMapSize) {
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/* And clear rest of color map: */
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for (i = NewColorMapSize; i < *ColorMapSize; i++)
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OutputColorMap[i].Red =
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OutputColorMap[i].Green =
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OutputColorMap[i].Blue = 0;
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}
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/* Average the colors in each entry to be the color to be used in the */
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/* output color map, and plug it into the output color map itself. */
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for (i = 0; i < NewColorMapSize; i++) {
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if ((j = NewColorSubdiv[i].NumEntries) > 0) {
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QuantizedColor = NewColorSubdiv[i].QuantizedColors;
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Red = Green = Blue = 0;
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while (QuantizedColor) {
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QuantizedColor -> NewColorIndex = i;
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Red += QuantizedColor -> RGB[0];
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Green += QuantizedColor -> RGB[1];
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Blue += QuantizedColor -> RGB[2];
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QuantizedColor = QuantizedColor -> Pnext;
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}
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OutputColorMap[i].Red = (Red << (8 - BITS_PER_PRIM_COLOR)) / j;
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OutputColorMap[i].Green = (Green << (8 - BITS_PER_PRIM_COLOR)) / j;
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OutputColorMap[i].Blue= (Blue << (8 - BITS_PER_PRIM_COLOR)) / j;
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}
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else
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GIF_MESSAGE("Null entry in quantized color map - thats weird.");
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}
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/* Finally scan the input buffer again and put the mapped index in the */
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/* output buffer. */
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MaxRGBError[0] = MaxRGBError[1] = MaxRGBError[2] = 0;
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for (i = 0; i < Width * Height; i++) {
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Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR))
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<< (2 * BITS_PER_PRIM_COLOR)) +
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((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR))
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<< BITS_PER_PRIM_COLOR) +
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(BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR));
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Index = ColorArrayEntries[Index].NewColorIndex;
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OutputBuffer[i] = Index;
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if (MaxRGBError[0] < ABS(OutputColorMap[Index].Red - RedInput[i]))
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MaxRGBError[0] = ABS(OutputColorMap[Index].Red - RedInput[i]);
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if (MaxRGBError[1] < ABS(OutputColorMap[Index].Green - GreenInput[i]))
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MaxRGBError[1] = ABS(OutputColorMap[Index].Green - GreenInput[i]);
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if (MaxRGBError[2] < ABS(OutputColorMap[Index].Blue - BlueInput[i]))
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MaxRGBError[2] = ABS(OutputColorMap[Index].Blue - BlueInput[i]);
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}
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#ifdef DEBUG
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fprintf(stderr,
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"Quantization L(0) errors: Red = %d, Green = %d, Blue = %d.\n",
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MaxRGBError[0], MaxRGBError[1], MaxRGBError[2]);
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#endif /* DEBUG */
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free((char *) ColorArrayEntries);
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*ColorMapSize = NewColorMapSize;
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return GIF_OK;
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}
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/******************************************************************************
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* Routine to subdivide the RGB space recursively using median cut in each *
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* axes alternatingly until ColorMapSize different cubes exists. *
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* The biggest cube in one dimension is subdivide unless it has only one entry.*
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* Returns GIF_ERROR if failed, otherwise GIF_OK. *
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******************************************************************************/
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static int SubdivColorMap(NewColorMapType *NewColorSubdiv,
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unsigned int ColorMapSize,
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unsigned int *NewColorMapSize)
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{
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int MaxSize;
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unsigned int i, j, Index = 0, NumEntries, MinColor, MaxColor;
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long Sum, Count;
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QuantizedColorType *QuantizedColor, **SortArray;
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while (ColorMapSize > *NewColorMapSize) {
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/* Find candidate for subdivision: */
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MaxSize = -1;
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for (i = 0; i < *NewColorMapSize; i++) {
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for (j = 0; j < 3; j++) {
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if (((int) NewColorSubdiv[i].RGBWidth[j]) > MaxSize &&
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NewColorSubdiv[i].NumEntries > 1) {
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MaxSize = NewColorSubdiv[i].RGBWidth[j];
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Index = i;
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SortRGBAxis = j;
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}
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}
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}
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if (MaxSize == -1)
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return GIF_OK;
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/* Split the entry Index into two along the axis SortRGBAxis: */
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/* Sort all elements in that entry along the given axis and split at */
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/* the median. */
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if ((SortArray = (QuantizedColorType **)
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malloc(sizeof(QuantizedColorType *) *
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NewColorSubdiv[Index].NumEntries)) == NULL)
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return GIF_ERROR;
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for (j = 0, QuantizedColor = NewColorSubdiv[Index].QuantizedColors;
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j < NewColorSubdiv[Index].NumEntries && QuantizedColor != NULL;
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j++, QuantizedColor = QuantizedColor -> Pnext)
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SortArray[j] = QuantizedColor;
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qsort(SortArray, NewColorSubdiv[Index].NumEntries,
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sizeof(QuantizedColorType *), SortCmpRtn);
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/* Relink the sorted list into one: */
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for (j = 0; j < NewColorSubdiv[Index].NumEntries - 1; j++)
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SortArray[j] -> Pnext = SortArray[j + 1];
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SortArray[NewColorSubdiv[Index].NumEntries - 1] -> Pnext = NULL;
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NewColorSubdiv[Index].QuantizedColors = QuantizedColor = SortArray[0];
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free((char *) SortArray);
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/* Now simply add the Counts until we have half of the Count: */
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Sum = NewColorSubdiv[Index].Count / 2 - QuantizedColor -> Count;
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NumEntries = 1;
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Count = QuantizedColor -> Count;
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while ((Sum -= QuantizedColor -> Pnext -> Count) >= 0 &&
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QuantizedColor -> Pnext != NULL &&
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QuantizedColor -> Pnext -> Pnext != NULL) {
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QuantizedColor = QuantizedColor -> Pnext;
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NumEntries++;
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Count += QuantizedColor -> Count;
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}
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/* Save the values of the last color of the first half, and first */
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/* of the second half so we can update the Bounding Boxes later. */
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/* Also as the colors are quantized and the BBoxes are full 0..255, */
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/* they need to be rescaled. */
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MaxColor = QuantizedColor -> RGB[SortRGBAxis];/* Max. of first half. */
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MinColor = QuantizedColor -> Pnext -> RGB[SortRGBAxis];/* of second. */
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MaxColor <<= (8 - BITS_PER_PRIM_COLOR);
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MinColor <<= (8 - BITS_PER_PRIM_COLOR);
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/* Partition right here: */
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NewColorSubdiv[*NewColorMapSize].QuantizedColors =
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QuantizedColor -> Pnext;
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QuantizedColor -> Pnext = NULL;
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NewColorSubdiv[*NewColorMapSize].Count = Count;
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NewColorSubdiv[Index].Count -= Count;
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NewColorSubdiv[*NewColorMapSize].NumEntries =
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NewColorSubdiv[Index].NumEntries - NumEntries;
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NewColorSubdiv[Index].NumEntries = NumEntries;
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for (j = 0; j < 3; j++) {
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NewColorSubdiv[*NewColorMapSize].RGBMin[j] =
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NewColorSubdiv[Index].RGBMin[j];
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NewColorSubdiv[*NewColorMapSize].RGBWidth[j] =
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NewColorSubdiv[Index].RGBWidth[j];
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}
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NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] =
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NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] +
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NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] -
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MinColor;
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NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] = MinColor;
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NewColorSubdiv[Index].RGBWidth[SortRGBAxis] =
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MaxColor - NewColorSubdiv[Index].RGBMin[SortRGBAxis];
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(*NewColorMapSize)++;
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}
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return GIF_OK;
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}
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/******************************************************************************
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* Routine called by qsort to compare to entries. *
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******************************************************************************/
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#ifdef __MSDOS__
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static int SortCmpRtn(const VoidPtr Entry1, const VoidPtr Entry2)
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#else
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static int SortCmpRtn(VoidPtr Entry1, VoidPtr Entry2)
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#endif /* __MSDOS__ */
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{
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return (* ((QuantizedColorType **) Entry1)) -> RGB[SortRGBAxis] -
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(* ((QuantizedColorType **) Entry2)) -> RGB[SortRGBAxis];
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}
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