/* @(#)root/x11:$Name$:$Id$ */
/* Author: Fons Rademakers 04/11/98*/
/*****************************************************************************
* Module to quantize 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. *
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
typedef unsigned char byte;
typedef struct GifColorType {
byte Red, Green, Blue;
} GifColorType;
#define ABS(x) ((x) > 0 ? (x) : (-(x)))
#define GIF_ERROR 0
#define GIF_OK 1
/* The colors are stripped to 5 bits per primary color */
#define COLOR_ARRAY_SIZE 32768
#define BITS_PER_PRIM_COLOR 5
#define MAX_PRIM_COLOR 0x1f
static int SortRGBAxis;
typedef struct QuantizedColorType {
byte RGB[3];
byte NewColorIndex;
long Count;
struct QuantizedColorType *Pnext;
} QuantizedColorType;
typedef struct NewColorMapType {
byte RGBMin[3], RGBWidth[3];
unsigned int NumEntries; /* # of QuantizedColorType in linked list below. */
long Count; /* Total number of pixels in all the entries. */
QuantizedColorType *QuantizedColors;
} NewColorMapType;
static int SubdivColorMap(NewColorMapType *NewColorSubdiv,
unsigned int ColorMapSize,
unsigned int *NewColorMapSize);
static int SortCmpRtn(const void *Entry1, const void *Entry2);
/******************************************************************************
* 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 GIFquantize(unsigned int Width, unsigned int Height, int *ColorMapSize,
byte *RedInput, byte *GreenInput, byte *BlueInput,
byte *OutputBuffer, GifColorType *OutputColorMap)
{
unsigned int Index, NumOfEntries, newsize;
int i, j, MaxRGBError[3];
int NewColorMapSize;
long Red, Green, Blue;
NewColorMapType NewColorSubdiv[256];
QuantizedColorType *ColorArrayEntries, *QuantizedColor;
if ((ColorArrayEntries = (QuantizedColorType *)
malloc(sizeof(QuantizedColorType) * COLOR_ARRAY_SIZE)) == NULL) {
fprintf(stderr, "QuantizeBuffer: not enough memory\n");
return GIF_ERROR;
}
for (i = 0; i < COLOR_ARRAY_SIZE; i++) {
ColorArrayEntries[i].RGB[0]= i >> (2 * BITS_PER_PRIM_COLOR);
ColorArrayEntries[i].RGB[1] = (i >> BITS_PER_PRIM_COLOR) & MAX_PRIM_COLOR;
ColorArrayEntries[i].RGB[2] = i & MAX_PRIM_COLOR;
ColorArrayEntries[i].Count = 0;
}
/* Sample the colors and their distribution: */
for (i = 0; i < (int)(Width * Height); i++) {
Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR))
<< (2 * BITS_PER_PRIM_COLOR)) +
((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR))
<< BITS_PER_PRIM_COLOR) +
(BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR));
ColorArrayEntries[Index].Count++;
}
/* Put all the colors in the first entry of the color map, and call the */
/* recursive subdivision process. */
for (i = 0; i < 256; i++) {
NewColorSubdiv[i].QuantizedColors = NULL;
NewColorSubdiv[i].Count = NewColorSubdiv[i].NumEntries = 0;
for (j = 0; j < 3; j++) {
NewColorSubdiv[i].RGBMin[j] = 0;
NewColorSubdiv[i].RGBWidth[j] = 255;
}
}
/* Find the non empty entries in the color table and chain them: */
for (i = 0; i < COLOR_ARRAY_SIZE; i++)
if (ColorArrayEntries[i].Count > 0) break;
QuantizedColor = NewColorSubdiv[0].QuantizedColors = &ColorArrayEntries[i];
NumOfEntries = 1;
while (++i < COLOR_ARRAY_SIZE)
if (ColorArrayEntries[i].Count > 0) {
QuantizedColor -> Pnext = &ColorArrayEntries[i];
QuantizedColor = &ColorArrayEntries[i];
NumOfEntries++;
}
QuantizedColor -> Pnext = NULL;
NewColorSubdiv[0].NumEntries = NumOfEntries;/* Different sampled colors. */
NewColorSubdiv[0].Count = ((long) Width) * Height; /* Pixels. */
newsize = 1;
if (SubdivColorMap(NewColorSubdiv, *ColorMapSize, &newsize) != GIF_OK) {
free((char *) ColorArrayEntries);
return GIF_ERROR;
}
NewColorMapSize = (int)newsize;
if (NewColorMapSize < *ColorMapSize) {
/* And clear rest of color map: */
for (i = NewColorMapSize; i < *ColorMapSize; i++)
OutputColorMap[i].Red =
OutputColorMap[i].Green =
OutputColorMap[i].Blue = 0;
}
/* Average the colors in each entry to be the color to be used in the */
/* output color map, and plug it into the output color map itself. */
for (i = 0; i < NewColorMapSize; i++) {
if ((j = NewColorSubdiv[i].NumEntries) > 0) {
QuantizedColor = NewColorSubdiv[i].QuantizedColors;
Red = Green = Blue = 0;
while (QuantizedColor) {
QuantizedColor -> NewColorIndex = i;
Red += QuantizedColor -> RGB[0];
Green += QuantizedColor -> RGB[1];
Blue += QuantizedColor -> RGB[2];
QuantizedColor = QuantizedColor -> Pnext;
}
OutputColorMap[i].Red = (Red << (8 - BITS_PER_PRIM_COLOR)) / j;
OutputColorMap[i].Green = (Green << (8 - BITS_PER_PRIM_COLOR)) / j;
OutputColorMap[i].Blue= (Blue << (8 - BITS_PER_PRIM_COLOR)) / j;
}
else
fprintf(stderr, "Null entry in quantized color map - thats weird.");
}
/* Finally scan the input buffer again and put the mapped index in the */
/* output buffer. */
MaxRGBError[0] = MaxRGBError[1] = MaxRGBError[2] = 0;
for (i = 0; i < (int)(Width * Height); i++) {
Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR))
<< (2 * BITS_PER_PRIM_COLOR)) +
((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR))
<< BITS_PER_PRIM_COLOR) +
(BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR));
Index = ColorArrayEntries[Index].NewColorIndex;
OutputBuffer[i] = Index;
if (MaxRGBError[0] < ABS(OutputColorMap[Index].Red - RedInput[i]))
MaxRGBError[0] = ABS(OutputColorMap[Index].Red - RedInput[i]);
if (MaxRGBError[1] < ABS(OutputColorMap[Index].Green - GreenInput[i]))
MaxRGBError[1] = ABS(OutputColorMap[Index].Green - GreenInput[i]);
if (MaxRGBError[2] < ABS(OutputColorMap[Index].Blue - BlueInput[i]))
MaxRGBError[2] = ABS(OutputColorMap[Index].Blue - BlueInput[i]);
}
#ifdef DEBUG
fprintf(stderr,
"Quantization L(0) errors: Red = %d, Green = %d, Blue = %d.\n",
MaxRGBError[0], MaxRGBError[1], MaxRGBError[2]);
#endif /* DEBUG */
free((char *) ColorArrayEntries);
*ColorMapSize = NewColorMapSize;
return GIF_OK;
}
/******************************************************************************
* Routine to subdivide the RGB space recursively using median cut in each *
* axes alternatingly until ColorMapSize different cubes exists. *
* The biggest cube in one dimension is subdivide unless it has only one entry.*
* Returns GIF_ERROR if failed, otherwise GIF_OK. *
******************************************************************************/
static int SubdivColorMap(NewColorMapType *NewColorSubdiv,
unsigned int ColorMapSize,
unsigned int *NewColorMapSize)
{
int MaxSize;
unsigned int i, j, Index = 0, NumEntries, MinColor, MaxColor;
long Sum, Count;
QuantizedColorType *QuantizedColor, **SortArray;
while (ColorMapSize > *NewColorMapSize) {
/* Find candidate for subdivision: */
MaxSize = -1;
for (i = 0; i < *NewColorMapSize; i++) {
for (j = 0; j < 3; j++) {
if (((int) NewColorSubdiv[i].RGBWidth[j]) > MaxSize &&
NewColorSubdiv[i].NumEntries > 1) {
MaxSize = NewColorSubdiv[i].RGBWidth[j];
Index = i;
SortRGBAxis = j;
}
}
}
if (MaxSize == -1)
return GIF_OK;
/* Split the entry Index into two along the axis SortRGBAxis: */
/* Sort all elements in that entry along the given axis and split at */
/* the median. */
if ((SortArray = (QuantizedColorType **)
malloc(sizeof(QuantizedColorType *) *
NewColorSubdiv[Index].NumEntries)) == NULL)
return GIF_ERROR;
for (j = 0, QuantizedColor = NewColorSubdiv[Index].QuantizedColors;
j < NewColorSubdiv[Index].NumEntries && QuantizedColor != NULL;
j++, QuantizedColor = QuantizedColor -> Pnext)
SortArray[j] = QuantizedColor;
qsort(SortArray, NewColorSubdiv[Index].NumEntries,
sizeof(QuantizedColorType *), SortCmpRtn);
/* Relink the sorted list into one: */
for (j = 0; j < NewColorSubdiv[Index].NumEntries - 1; j++)
SortArray[j] -> Pnext = SortArray[j + 1];
SortArray[NewColorSubdiv[Index].NumEntries - 1] -> Pnext = NULL;
NewColorSubdiv[Index].QuantizedColors = QuantizedColor = SortArray[0];
free((char *) SortArray);
/* Now simply add the Counts until we have half of the Count: */
Sum = NewColorSubdiv[Index].Count / 2 - QuantizedColor -> Count;
NumEntries = 1;
Count = QuantizedColor -> Count;
while ((Sum -= QuantizedColor -> Pnext -> Count) >= 0 &&
QuantizedColor -> Pnext != NULL &&
QuantizedColor -> Pnext -> Pnext != NULL) {
QuantizedColor = QuantizedColor -> Pnext;
NumEntries++;
Count += QuantizedColor -> Count;
}
/* Save the values of the last color of the first half, and first */
/* of the second half so we can update the Bounding Boxes later. */
/* Also as the colors are quantized and the BBoxes are full 0..255, */
/* they need to be rescaled. */
MaxColor = QuantizedColor -> RGB[SortRGBAxis];/* Max. of first half. */
MinColor = QuantizedColor -> Pnext -> RGB[SortRGBAxis];/* of second. */
MaxColor <<= (8 - BITS_PER_PRIM_COLOR);
MinColor <<= (8 - BITS_PER_PRIM_COLOR);
/* Partition right here: */
NewColorSubdiv[*NewColorMapSize].QuantizedColors =
QuantizedColor -> Pnext;
QuantizedColor -> Pnext = NULL;
NewColorSubdiv[*NewColorMapSize].Count = Count;
NewColorSubdiv[Index].Count -= Count;
NewColorSubdiv[*NewColorMapSize].NumEntries =
NewColorSubdiv[Index].NumEntries - NumEntries;
NewColorSubdiv[Index].NumEntries = NumEntries;
for (j = 0; j < 3; j++) {
NewColorSubdiv[*NewColorMapSize].RGBMin[j] =
NewColorSubdiv[Index].RGBMin[j];
NewColorSubdiv[*NewColorMapSize].RGBWidth[j] =
NewColorSubdiv[Index].RGBWidth[j];
}
NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] =
NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] +
NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] -
MinColor;
NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] = MinColor;
NewColorSubdiv[Index].RGBWidth[SortRGBAxis] =
MaxColor - NewColorSubdiv[Index].RGBMin[SortRGBAxis];
(*NewColorMapSize)++;
}
return GIF_OK;
}
/******************************************************************************
* Routine called by qsort to compare to entries. *
******************************************************************************/
static int SortCmpRtn(const void *Entry1, const void *Entry2)
{
return (* ((QuantizedColorType **) Entry1)) -> RGB[SortRGBAxis] -
(* ((QuantizedColorType **) Entry2)) -> RGB[SortRGBAxis];
}
