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Refactor GetColorPalette method.

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This was defined (slightly differently) at two places. Created a common
method and moved to utils/utils.[hc].

Change-Id: I19adc9c48f2a4e2ec9d995e78add6f25172774c2
This commit is contained in:
Urvang Joshi
2016-05-18 14:27:15 -07:00
parent e15afbce5d
commit 169004b1d5
4 changed files with 85 additions and 104 deletions
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66
src/utils/utils.c
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@ -15,6 +15,7 @@
#include <string.h> // for memcpy()
#include "../webp/decode.h"
#include "../webp/encode.h"
#include "../webp/format_constants.h" // for MAX_PALETTE_SIZE
#include "./utils.h"
// If PRINT_MEM_INFO is defined, extra info (like total memory used, number of
@ -237,3 +238,68 @@ void WebPCopyPixels(const WebPPicture* const src, WebPPicture* const dst) {
}
//------------------------------------------------------------------------------
#define MAX_COLOR_COUNT MAX_PALETTE_SIZE
#define COLOR_HASH_SIZE (MAX_COLOR_COUNT * 4)
#define COLOR_HASH_RIGHT_SHIFT 22 // 32 - log2(COLOR_HASH_SIZE).
int WebPGetColorPalette(const WebPPicture* const pic, uint32_t* const palette) {
int i;
int x, y;
int num_colors = 0;
uint8_t in_use[COLOR_HASH_SIZE] = { 0 };
uint32_t colors[COLOR_HASH_SIZE];
static const uint32_t kHashMul = 0x1e35a7bdU;
const uint32_t* argb = pic->argb;
const int width = pic->width;
const int height = pic->height;
uint32_t last_pix = ~argb[0]; // so we're sure that last_pix != argb[0]
assert(pic != NULL);
assert(pic->use_argb);
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
int key;
if (argb[x] == last_pix) {
continue;
}
last_pix = argb[x];
key = (kHashMul * last_pix) >> COLOR_HASH_RIGHT_SHIFT;
while (1) {
if (!in_use[key]) {
colors[key] = last_pix;
in_use[key] = 1;
++num_colors;
if (num_colors > MAX_COLOR_COUNT) {
return MAX_COLOR_COUNT + 1; // Exact count not needed.
}
break;
} else if (colors[key] == last_pix) {
break; // The color is already there.
} else {
// Some other color sits here, so do linear conflict resolution.
++key;
key &= (COLOR_HASH_SIZE - 1); // Key mask.
}
}
}
argb += pic->argb_stride;
}
if (palette != NULL) { // Fill the colors into palette.
num_colors = 0;
for (i = 0; i < COLOR_HASH_SIZE; ++i) {
if (in_use[i]) {
palette[num_colors] = colors[i];
++num_colors;
}
}
}
return num_colors;
}
#undef MAX_COLOR_COUNT
#undef COLOR_HASH_SIZE
#undef COLOR_HASH_RIGHT_SHIFT
//------------------------------------------------------------------------------