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Refactor palette sorting computation.

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This will ease the integration of new methods.

Change-Id: Icec3eddaa4ab9030d28ccfe579eb6dc13ded2f02
This commit is contained in:
Vincent Rabaud
2023-07-26 09:16:07 +02:00
parent af7fbfd2d9
commit 1432ebbadb
3 changed files with 66 additions and 44 deletions
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28
src/utils/palette.h
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@ -21,9 +21,15 @@ struct WebPPicture;
// The different ways a palette can be sorted.
typedef enum PaletteSorting {
kSortedDefault = 0,
// Sorts by minimizing L1 deltas between consecutive colors, giving more
// weight to RGB colors.
kMinimizeDelta = 1,
// Implements the modified Zeng method from "A Survey on Palette Reordering
// Methods for Improving the Compression of Color-Indexed Images" by Armando
// J. Pinho and Antonio J. R. Neves.
kModifiedZeng = 2,
kUnusedPalette = 3
kUnusedPalette = 3,
kPaletteSortingNum = 4
} PaletteSorting;
// Returns the index of 'color' in the sorted palette 'sorted' of size
@ -44,19 +50,11 @@ void PrepareMapToPalette(const uint32_t palette[], uint32_t num_colors,
int GetColorPalette(const struct WebPPicture* const pic,
uint32_t* const palette);
// Sorts the color sorted palette in 'palette_sorted'/'num_colors' by
// minimizing deltas between consecutive colors and stores it in 'palette'.
void PaletteSortMinimizeDeltas(const uint32_t* const palette_sorted,
int num_colors, uint32_t* const palette);
// Implements the modified Zeng method from "A Survey on Palette Reordering
// Methods for Improving the Compression of Color-Indexed Images" by Armando J.
// Pinho and Antonio J. R. Neves. The palette defined by 'palette_in' and
// 'num_colors' is sorted using information from 'pic' and output in
// 'palette'.
// Returns 0 on memory allocation error.
int PaletteSortModifiedZeng(const struct WebPPicture* const pic,
const uint32_t* const palette_in,
uint32_t num_colors, uint32_t* const palette);
// Sorts the palette according to the criterion defined by 'method'.
// 'palette_sorted' is the input palette sorted lexicographically, as done in
// PrepareMapToPalette. Returns 0 on memory allocation error.
int PaletteSort(PaletteSorting method, const struct WebPPicture* pic,
const uint32_t* palette_sorted, uint32_t num_colors,
uint32_t* palette);
#endif // WEBP_UTILS_PALETTE_H_