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101 lines
2.5 KiB
101 lines
2.5 KiB
#include "utils/sdl_bilinear_scale.hpp" |
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#include <cstdint> |
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#include <memory> |
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// Performs bilinear scaling using fixed-width integer math. |
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namespace devilution { |
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namespace { |
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unsigned Frac(unsigned fixedPoint) |
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{ |
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return fixedPoint & 0xffff; |
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} |
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unsigned ToInt(unsigned fixedPoint) |
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{ |
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return fixedPoint >> 16; |
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} |
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std::unique_ptr<unsigned[]> CreateMixFactors(unsigned srcSize, unsigned dstSize) |
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{ |
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std::unique_ptr<unsigned[]> result { new unsigned[dstSize + 1] }; |
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const auto scale = static_cast<unsigned>(65536.0 * static_cast<float>(srcSize - 1) / dstSize); |
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unsigned mix = 0; |
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for (unsigned i = 0; i <= dstSize; ++i) { |
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result[i] = mix; |
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mix = Frac(mix) + scale; |
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} |
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return result; |
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}; |
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std::uint8_t MixColors(std::uint8_t first, std::uint8_t second, unsigned ratio) |
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{ |
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return ToInt((second - first) * ratio) + first; |
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} |
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} // namespace |
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void BilinearScale32(SDL_Surface *src, SDL_Surface *dst) |
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{ |
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const std::unique_ptr<unsigned[]> mixXs = CreateMixFactors(src->w, dst->w); |
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const std::unique_ptr<unsigned[]> mixYs = CreateMixFactors(src->h, dst->h); |
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const unsigned dgap = dst->pitch - dst->w * 4; |
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auto *srcPixels = static_cast<std::uint8_t *>(src->pixels); |
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auto *dstPixels = static_cast<std::uint8_t *>(dst->pixels); |
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unsigned *curMixY = &mixYs[0]; |
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unsigned srcY = 0; |
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for (unsigned y = 0; y < static_cast<unsigned>(dst->h); ++y) { |
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std::uint8_t *s[4] = { |
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srcPixels, // Self |
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srcPixels + 4, // Right |
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srcPixels + src->pitch, // Bottom |
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srcPixels + src->pitch + 4 // Bottom right |
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}; |
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unsigned *curMixX = &mixXs[0]; |
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unsigned srcX = 0; |
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for (unsigned x = 0; x < static_cast<unsigned>(dst->w); ++x) { |
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const unsigned mixX = Frac(*curMixX); |
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const unsigned mixY = Frac(*curMixY); |
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for (unsigned channel = 0; channel < 4; ++channel) { |
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dstPixels[channel] = MixColors( |
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MixColors(s[0][channel], s[1][channel], mixX), |
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MixColors(s[2][channel], s[3][channel], mixX), |
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mixY); |
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} |
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++curMixX; |
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if (*curMixX > 0) { |
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unsigned step = ToInt(*curMixX); |
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srcX += step; |
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if (srcX <= static_cast<unsigned>(src->w)) { |
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step *= 4; |
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for (auto &v : s) { |
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v += step; |
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} |
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} |
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} |
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dstPixels += 4; |
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} |
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++curMixY; |
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if (*curMixY > 0) { |
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const unsigned step = ToInt(*curMixY); |
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srcY += step; |
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if (srcY < static_cast<unsigned>(src->h)) { |
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srcPixels += step * src->pitch; |
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} |
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} |
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dstPixels += dgap; |
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} |
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} |
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} // namespace devilution
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