331 lines
13 KiB
C
331 lines
13 KiB
C
/*****************************************************************************
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quantize.c - quantize a high resolution image into lower one
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Based on: "Color Image Quantization for frame buffer Display", by
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Paul Heckbert SIGGRAPH 1982 page 297-307.
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This doesn't really belong in the core library, was undocumented,
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and was removed in 4.2. Then it turned out some client apps were
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actually using it, so it was restored in 5.0.
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******************************************************************************/
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#include <stdlib.h>
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#include <stdio.h>
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#include "gif_lib.h"
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#include "gif_lib_private.h"
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#define ABS(x) ((x) > 0 ? (x) : (-(x)))
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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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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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unsigned 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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static int SortCmpRtn(const void *Entry1, const void *Entry2);
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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 successful, GIF_ERROR otherwise.
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******************************************************************************/
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int
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GifQuantizeBuffer(unsigned int Width,
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unsigned int Height,
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int *ColorMapSize,
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GifByteType * RedInput,
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GifByteType * GreenInput,
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GifByteType * BlueInput,
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GifByteType * OutputBuffer,
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GifColorType * OutputColorMap) {
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unsigned int Index, NumOfEntries;
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int i, j, MaxRGBError[3];
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unsigned int NewColorMapSize;
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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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ColorArrayEntries = (QuantizedColorType *)malloc(
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sizeof(QuantizedColorType) * COLOR_ARRAY_SIZE);
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if (ColorArrayEntries == NULL) {
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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 < (int)(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)
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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 = 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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}
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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 < (int)(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
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SubdivColorMap(NewColorMapType * NewColorSubdiv,
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unsigned int ColorMapSize,
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unsigned int *NewColorMapSize) {
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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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SortArray = (QuantizedColorType **)malloc(
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sizeof(QuantizedColorType *) *
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NewColorSubdiv[Index].NumEntries);
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if (SortArray == 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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/*
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* Because qsort isn't stable, this can produce differing
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* results for the order of tuples depending on platform
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* details of how qsort() is implemented.
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*
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* We mitigate this problem by sorting on all three axes rather
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* than only the one specied by SortRGBAxis; that way the instability
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* can only become an issue if there are multiple color indices
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* referring to identical RGB tuples. Older versions of this
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* sorted on only the one axis.
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*/
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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 (QuantizedColor->Pnext != NULL &&
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(Sum -= QuantizedColor->Pnext->Count) >= 0 &&
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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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*/
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MaxColor = QuantizedColor->RGB[SortRGBAxis]; /* Max. of first half */
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/* coverity[var_deref_op] */
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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] - 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 two entries.
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*****************************************************************************/
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static int
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SortCmpRtn(const void *Entry1,
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const void *Entry2) {
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QuantizedColorType *entry1 = (*((QuantizedColorType **) Entry1));
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QuantizedColorType *entry2 = (*((QuantizedColorType **) Entry2));
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/* sort on all axes of the color space! */
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int hash1 = entry1->RGB[SortRGBAxis] * 256 * 256
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+ entry1->RGB[(SortRGBAxis+1) % 3] * 256
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+ entry1->RGB[(SortRGBAxis+2) % 3];
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int hash2 = entry2->RGB[SortRGBAxis] * 256 * 256
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+ entry2->RGB[(SortRGBAxis+1) % 3] * 256
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+ entry2->RGB[(SortRGBAxis+2) % 3];
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return hash1 - hash2;
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}
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/* end */
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