1 /***************************************************************************** 2 3 quantize.c - quantize a high resolution image into lower one 4 5 Based on: "Color Image Quantization for frame buffer Display", by 6 Paul Heckbert SIGGRAPH 1982 page 297-307. 7 8 This doesn't really belong in the core library, was undocumented, 9 and was removed in 4.2. Then it turned out some client apps were 10 actually using it, so it was restored in 5.0. 11 12 ******************************************************************************/ 13 14 #include <stdlib.h> 15 #include <stdio.h> 16 #include "gif_lib.h" 17 #include "gif_lib_private.h" 18 19 #define ABS(x) ((x) > 0 ? (x) : (-(x))) 20 21 #define COLOR_ARRAY_SIZE 32768 22 #define BITS_PER_PRIM_COLOR 5 23 #define MAX_PRIM_COLOR 0x1f 24 25 static int SortRGBAxis; 26 27 typedef struct QuantizedColorType { 28 GifByteType RGB[3]; 29 GifByteType NewColorIndex; 30 long Count; 31 struct QuantizedColorType *Pnext; 32 } QuantizedColorType; 33 34 typedef struct NewColorMapType { 35 GifByteType RGBMin[3], RGBWidth[3]; 36 unsigned int NumEntries; /* # of QuantizedColorType in linked list below */ 37 unsigned long Count; /* Total number of pixels in all the entries */ 38 QuantizedColorType *QuantizedColors; 39 } NewColorMapType; 40 41 static int SubdivColorMap(NewColorMapType * NewColorSubdiv, 42 unsigned int ColorMapSize, 43 unsigned int *NewColorMapSize); 44 static int SortCmpRtn(const void *Entry1, const void *Entry2); 45 46 /****************************************************************************** 47 Quantize high resolution image into lower one. Input image consists of a 48 2D array for each of the RGB colors with size Width by Height. There is no 49 Color map for the input. Output is a quantized image with 2D array of 50 indexes into the output color map. 51 Note input image can be 24 bits at the most (8 for red/green/blue) and 52 the output has 256 colors at the most (256 entries in the color map.). 53 ColorMapSize specifies size of color map up to 256 and will be updated to 54 real size before returning. 55 Also non of the parameter are allocated by this routine. 56 This function returns GIF_OK if successful, GIF_ERROR otherwise. 57 ******************************************************************************/ 58 int 59 GifQuantizeBuffer(unsigned int Width, 60 unsigned int Height, 61 int *ColorMapSize, 62 GifByteType * RedInput, 63 GifByteType * GreenInput, 64 GifByteType * BlueInput, 65 GifByteType * OutputBuffer, 66 GifColorType * OutputColorMap) { 67 68 unsigned int Index, NumOfEntries; 69 int i, j, MaxRGBError[3]; 70 unsigned int NewColorMapSize; 71 long Red, Green, Blue; 72 NewColorMapType NewColorSubdiv[256]; 73 QuantizedColorType *ColorArrayEntries, *QuantizedColor; 74 75 ColorArrayEntries = (QuantizedColorType *)malloc( 76 sizeof(QuantizedColorType) * COLOR_ARRAY_SIZE); 77 if (ColorArrayEntries == NULL) { 78 return GIF_ERROR; 79 } 80 81 for (i = 0; i < COLOR_ARRAY_SIZE; i++) { 82 ColorArrayEntries[i].RGB[0] = i >> (2 * BITS_PER_PRIM_COLOR); 83 ColorArrayEntries[i].RGB[1] = (i >> BITS_PER_PRIM_COLOR) & 84 MAX_PRIM_COLOR; 85 ColorArrayEntries[i].RGB[2] = i & MAX_PRIM_COLOR; 86 ColorArrayEntries[i].Count = 0; 87 } 88 89 /* Sample the colors and their distribution: */ 90 for (i = 0; i < (int)(Width * Height); i++) { 91 Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR)) << 92 (2 * BITS_PER_PRIM_COLOR)) + 93 ((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR)) << 94 BITS_PER_PRIM_COLOR) + 95 (BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR)); 96 ColorArrayEntries[Index].Count++; 97 } 98 99 /* Put all the colors in the first entry of the color map, and call the 100 * recursive subdivision process. */ 101 for (i = 0; i < 256; i++) { 102 NewColorSubdiv[i].QuantizedColors = NULL; 103 NewColorSubdiv[i].Count = NewColorSubdiv[i].NumEntries = 0; 104 for (j = 0; j < 3; j++) { 105 NewColorSubdiv[i].RGBMin[j] = 0; 106 NewColorSubdiv[i].RGBWidth[j] = 255; 107 } 108 } 109 110 /* Find the non empty entries in the color table and chain them: */ 111 for (i = 0; i < COLOR_ARRAY_SIZE; i++) 112 if (ColorArrayEntries[i].Count > 0) 113 break; 114 QuantizedColor = NewColorSubdiv[0].QuantizedColors = &ColorArrayEntries[i]; 115 NumOfEntries = 1; 116 while (++i < COLOR_ARRAY_SIZE) 117 if (ColorArrayEntries[i].Count > 0) { 118 QuantizedColor->Pnext = &ColorArrayEntries[i]; 119 QuantizedColor = &ColorArrayEntries[i]; 120 NumOfEntries++; 121 } 122 QuantizedColor->Pnext = NULL; 123 124 NewColorSubdiv[0].NumEntries = NumOfEntries; /* Different sampled colors */ 125 NewColorSubdiv[0].Count = ((long)Width) * Height; /* Pixels */ 126 NewColorMapSize = 1; 127 if (SubdivColorMap(NewColorSubdiv, *ColorMapSize, &NewColorMapSize) != 128 GIF_OK) { 129 free((char *)ColorArrayEntries); 130 return GIF_ERROR; 131 } 132 if (NewColorMapSize < *ColorMapSize) { 133 /* And clear rest of color map: */ 134 for (i = NewColorMapSize; i < *ColorMapSize; i++) 135 OutputColorMap[i].Red = OutputColorMap[i].Green = 136 OutputColorMap[i].Blue = 0; 137 } 138 139 /* Average the colors in each entry to be the color to be used in the 140 * output color map, and plug it into the output color map itself. */ 141 for (i = 0; i < NewColorMapSize; i++) { 142 if ((j = NewColorSubdiv[i].NumEntries) > 0) { 143 QuantizedColor = NewColorSubdiv[i].QuantizedColors; 144 Red = Green = Blue = 0; 145 while (QuantizedColor) { 146 QuantizedColor->NewColorIndex = i; 147 Red += QuantizedColor->RGB[0]; 148 Green += QuantizedColor->RGB[1]; 149 Blue += QuantizedColor->RGB[2]; 150 QuantizedColor = QuantizedColor->Pnext; 151 } 152 OutputColorMap[i].Red = (Red << (8 - BITS_PER_PRIM_COLOR)) / j; 153 OutputColorMap[i].Green = (Green << (8 - BITS_PER_PRIM_COLOR)) / j; 154 OutputColorMap[i].Blue = (Blue << (8 - BITS_PER_PRIM_COLOR)) / j; 155 } 156 } 157 158 /* Finally scan the input buffer again and put the mapped index in the 159 * output buffer. */ 160 MaxRGBError[0] = MaxRGBError[1] = MaxRGBError[2] = 0; 161 for (i = 0; i < (int)(Width * Height); i++) { 162 Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR)) << 163 (2 * BITS_PER_PRIM_COLOR)) + 164 ((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR)) << 165 BITS_PER_PRIM_COLOR) + 166 (BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR)); 167 Index = ColorArrayEntries[Index].NewColorIndex; 168 OutputBuffer[i] = Index; 169 if (MaxRGBError[0] < ABS(OutputColorMap[Index].Red - RedInput[i])) 170 MaxRGBError[0] = ABS(OutputColorMap[Index].Red - RedInput[i]); 171 if (MaxRGBError[1] < ABS(OutputColorMap[Index].Green - GreenInput[i])) 172 MaxRGBError[1] = ABS(OutputColorMap[Index].Green - GreenInput[i]); 173 if (MaxRGBError[2] < ABS(OutputColorMap[Index].Blue - BlueInput[i])) 174 MaxRGBError[2] = ABS(OutputColorMap[Index].Blue - BlueInput[i]); 175 } 176 177 #ifdef DEBUG 178 fprintf(stderr, 179 "Quantization L(0) errors: Red = %d, Green = %d, Blue = %d.\n", 180 MaxRGBError[0], MaxRGBError[1], MaxRGBError[2]); 181 #endif /* DEBUG */ 182 183 free((char *)ColorArrayEntries); 184 185 *ColorMapSize = NewColorMapSize; 186 187 return GIF_OK; 188 } 189 190 /****************************************************************************** 191 Routine to subdivide the RGB space recursively using median cut in each 192 axes alternatingly until ColorMapSize different cubes exists. 193 The biggest cube in one dimension is subdivide unless it has only one entry. 194 Returns GIF_ERROR if failed, otherwise GIF_OK. 195 *******************************************************************************/ 196 static int 197 SubdivColorMap(NewColorMapType * NewColorSubdiv, 198 unsigned int ColorMapSize, 199 unsigned int *NewColorMapSize) { 200 201 int MaxSize; 202 unsigned int i, j, Index = 0, NumEntries, MinColor, MaxColor; 203 long Sum, Count; 204 QuantizedColorType *QuantizedColor, **SortArray; 205 206 while (ColorMapSize > *NewColorMapSize) { 207 /* Find candidate for subdivision: */ 208 MaxSize = -1; 209 for (i = 0; i < *NewColorMapSize; i++) { 210 for (j = 0; j < 3; j++) { 211 if ((((int)NewColorSubdiv[i].RGBWidth[j]) > MaxSize) && 212 (NewColorSubdiv[i].NumEntries > 1)) { 213 MaxSize = NewColorSubdiv[i].RGBWidth[j]; 214 Index = i; 215 SortRGBAxis = j; 216 } 217 } 218 } 219 220 if (MaxSize == -1) 221 return GIF_OK; 222 223 /* Split the entry Index into two along the axis SortRGBAxis: */ 224 225 /* Sort all elements in that entry along the given axis and split at 226 * the median. */ 227 SortArray = (QuantizedColorType **)malloc( 228 sizeof(QuantizedColorType *) * 229 NewColorSubdiv[Index].NumEntries); 230 if (SortArray == NULL) 231 return GIF_ERROR; 232 for (j = 0, QuantizedColor = NewColorSubdiv[Index].QuantizedColors; 233 j < NewColorSubdiv[Index].NumEntries && QuantizedColor != NULL; 234 j++, QuantizedColor = QuantizedColor->Pnext) 235 SortArray[j] = QuantizedColor; 236 237 qsort(SortArray, NewColorSubdiv[Index].NumEntries, 238 sizeof(QuantizedColorType *), SortCmpRtn); 239 240 /* Relink the sorted list into one: */ 241 for (j = 0; j < NewColorSubdiv[Index].NumEntries - 1; j++) 242 SortArray[j]->Pnext = SortArray[j + 1]; 243 SortArray[NewColorSubdiv[Index].NumEntries - 1]->Pnext = NULL; 244 NewColorSubdiv[Index].QuantizedColors = QuantizedColor = SortArray[0]; 245 free((char *)SortArray); 246 247 /* Now simply add the Counts until we have half of the Count: */ 248 Sum = NewColorSubdiv[Index].Count / 2 - QuantizedColor->Count; 249 NumEntries = 1; 250 Count = QuantizedColor->Count; 251 while (QuantizedColor->Pnext != NULL && 252 (Sum -= QuantizedColor->Pnext->Count) >= 0 && 253 QuantizedColor->Pnext->Pnext != NULL) { 254 QuantizedColor = QuantizedColor->Pnext; 255 NumEntries++; 256 Count += QuantizedColor->Count; 257 } 258 /* Save the values of the last color of the first half, and first 259 * of the second half so we can update the Bounding Boxes later. 260 * Also as the colors are quantized and the BBoxes are full 0..255, 261 * they need to be rescaled. 262 */ 263 MaxColor = QuantizedColor->RGB[SortRGBAxis]; /* Max. of first half */ 264 /* coverity[var_deref_op] */ 265 MinColor = QuantizedColor->Pnext->RGB[SortRGBAxis]; /* of second */ 266 MaxColor <<= (8 - BITS_PER_PRIM_COLOR); 267 MinColor <<= (8 - BITS_PER_PRIM_COLOR); 268 269 /* Partition right here: */ 270 NewColorSubdiv[*NewColorMapSize].QuantizedColors = 271 QuantizedColor->Pnext; 272 QuantizedColor->Pnext = NULL; 273 NewColorSubdiv[*NewColorMapSize].Count = Count; 274 NewColorSubdiv[Index].Count -= Count; 275 NewColorSubdiv[*NewColorMapSize].NumEntries = 276 NewColorSubdiv[Index].NumEntries - NumEntries; 277 NewColorSubdiv[Index].NumEntries = NumEntries; 278 for (j = 0; j < 3; j++) { 279 NewColorSubdiv[*NewColorMapSize].RGBMin[j] = 280 NewColorSubdiv[Index].RGBMin[j]; 281 NewColorSubdiv[*NewColorMapSize].RGBWidth[j] = 282 NewColorSubdiv[Index].RGBWidth[j]; 283 } 284 NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] = 285 NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] + 286 NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] - MinColor; 287 NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] = MinColor; 288 289 NewColorSubdiv[Index].RGBWidth[SortRGBAxis] = 290 MaxColor - NewColorSubdiv[Index].RGBMin[SortRGBAxis]; 291 292 (*NewColorMapSize)++; 293 } 294 295 return GIF_OK; 296 } 297 298 /**************************************************************************** 299 Routine called by qsort to compare two entries. 300 *****************************************************************************/ 301 static int 302 SortCmpRtn(const void *Entry1, 303 const void *Entry2) { 304 305 return (*((QuantizedColorType **) Entry1))->RGB[SortRGBAxis] - 306 (*((QuantizedColorType **) Entry2))->RGB[SortRGBAxis]; 307 } 308 309 /* end */ 310
