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116 lines
3.6 KiB
116 lines
3.6 KiB
#include "utils/palette_blending.hpp" |
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#include <cstdint> |
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#include <limits> |
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#include <SDL.h> |
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namespace devilution { |
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// This array is read from a lot on every frame. |
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// We do not use `std::array` here to improve debug build performance. |
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// In a debug build, `std::array` accesses are function calls. |
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uint8_t paletteTransparencyLookup[256][256]; |
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#if DEVILUTIONX_PALETTE_TRANSPARENCY_BLACK_16_LUT |
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uint16_t paletteTransparencyLookupBlack16[65536]; |
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#endif |
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namespace { |
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struct RGB { |
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uint8_t r; |
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uint8_t g; |
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uint8_t b; |
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}; |
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uint8_t FindBestMatchForColor(SDL_Color palette[256], RGB color, int skipFrom, int skipTo) |
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{ |
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uint8_t best; |
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uint32_t bestDiff = std::numeric_limits<uint32_t>::max(); |
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for (int i = 0; i < 256; i++) { |
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if (i >= skipFrom && i <= skipTo) |
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continue; |
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const int diffr = palette[i].r - color.r; |
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const int diffg = palette[i].g - color.g; |
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const int diffb = palette[i].b - color.b; |
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const uint32_t diff = diffr * diffr + diffg * diffg + diffb * diffb; |
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if (bestDiff > diff) { |
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best = i; |
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bestDiff = diff; |
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} |
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} |
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return best; |
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} |
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RGB BlendColors(const SDL_Color &a, const SDL_Color &b) |
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{ |
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return RGB { |
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.r = static_cast<uint8_t>((static_cast<int>(a.r) + static_cast<int>(b.r)) / 2), |
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.g = static_cast<uint8_t>((static_cast<int>(a.g) + static_cast<int>(b.g)) / 2), |
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.b = static_cast<uint8_t>((static_cast<int>(a.b) + static_cast<int>(b.b)) / 2), |
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}; |
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} |
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} // namespace |
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void GenerateBlendedLookupTable(SDL_Color palette[256], int skipFrom, int skipTo) |
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{ |
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for (unsigned i = 0; i < 256; i++) { |
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for (unsigned j = 0; j < 256; j++) { |
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if (i == j) { // No need to calculate transparency between 2 identical colors |
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paletteTransparencyLookup[i][j] = j; |
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continue; |
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} |
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if (i > j) { // Half the blends will be mirror identical ([i][j] is the same as [j][i]), so simply copy the existing combination. |
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paletteTransparencyLookup[i][j] = paletteTransparencyLookup[j][i]; |
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continue; |
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} |
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const uint8_t best = FindBestMatchForColor(palette, BlendColors(palette[i], palette[j]), skipFrom, skipTo); |
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paletteTransparencyLookup[i][j] = best; |
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} |
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} |
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#if DEVILUTIONX_PALETTE_TRANSPARENCY_BLACK_16_LUT |
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for (unsigned i = 0; i < 256; ++i) { |
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for (unsigned j = 0; j < 256; ++j) { |
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const uint16_t index = i | (j << 8U); |
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paletteTransparencyLookupBlack16[index] = paletteTransparencyLookup[0][i] | (paletteTransparencyLookup[0][j] << 8); |
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} |
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} |
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#endif |
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} |
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void UpdateBlendedLookupTableSingleColor(unsigned i, SDL_Color palette[256], int skipFrom, int skipTo) |
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{ |
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// Update blended transparency, but only for the color that was updated |
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for (unsigned j = 0; j < 256; j++) { |
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if (i == j) { // No need to calculate transparency between 2 identical colors |
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paletteTransparencyLookup[i][j] = j; |
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continue; |
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} |
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const uint8_t best = FindBestMatchForColor(palette, BlendColors(palette[i], palette[j]), skipFrom, skipTo); |
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paletteTransparencyLookup[i][j] = paletteTransparencyLookup[j][i] = best; |
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} |
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#if DEVILUTIONX_PALETTE_TRANSPARENCY_BLACK_16_LUT |
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UpdateTransparencyLookupBlack16(i, i); |
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#endif |
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} |
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#if DEVILUTIONX_PALETTE_TRANSPARENCY_BLACK_16_LUT |
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void UpdateTransparencyLookupBlack16(unsigned from, unsigned to) |
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{ |
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for (unsigned i = from; i <= to; i++) { |
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for (unsigned j = 0; j < 256; j++) { |
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const uint16_t index = i | (j << 8U); |
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const uint16_t reverseIndex = j | (i << 8U); |
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paletteTransparencyLookupBlack16[index] = paletteTransparencyLookup[0][i] | (paletteTransparencyLookup[0][j] << 8); |
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paletteTransparencyLookupBlack16[reverseIndex] = paletteTransparencyLookup[0][j] | (paletteTransparencyLookup[0][i] << 8); |
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} |
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} |
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} |
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#endif |
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} // namespace devilution
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