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Correction for alpha blending issues in texture mod compositing (#9029)
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@ -1811,6 +1811,24 @@ bool TextureSource::generateImagePart(std::string part_of_name,
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return true;
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}
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/*
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Calculate the color of a single pixel drawn on top of another pixel.
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This is a little more complicated than just video::SColor::getInterpolated
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because getInterpolated does not handle alpha correctly. For example, a
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pixel with alpha=64 drawn atop a pixel with alpha=128 should yield a
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pixel with alpha=160, while getInterpolated would yield alpha=96.
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*/
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static inline video::SColor blitPixel(const video::SColor &src_c, const video::SColor &dst_c, u32 ratio)
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{
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if (dst_c.getAlpha() == 0)
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return src_c;
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video::SColor out_c = src_c.getInterpolated(dst_c, (float)ratio / 255.0f);
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out_c.setAlpha(dst_c.getAlpha() + (255 - dst_c.getAlpha()) *
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src_c.getAlpha() * ratio / (255 * 255));
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return out_c;
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}
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/*
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Draw an image on top of an another one, using the alpha channel of the
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source image
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@ -1830,7 +1848,7 @@ static void blit_with_alpha(video::IImage *src, video::IImage *dst,
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s32 dst_y = dst_pos.Y + y0;
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video::SColor src_c = src->getPixel(src_x, src_y);
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video::SColor dst_c = dst->getPixel(dst_x, dst_y);
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dst_c = src_c.getInterpolated(dst_c, (float)src_c.getAlpha()/255.0f);
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dst_c = blitPixel(src_c, dst_c, src_c.getAlpha());
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dst->setPixel(dst_x, dst_y, dst_c);
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}
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}
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@ -1853,7 +1871,7 @@ static void blit_with_alpha_overlay(video::IImage *src, video::IImage *dst,
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video::SColor dst_c = dst->getPixel(dst_x, dst_y);
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if (dst_c.getAlpha() == 255 && src_c.getAlpha() != 0)
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{
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dst_c = src_c.getInterpolated(dst_c, (float)src_c.getAlpha()/255.0f);
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dst_c = blitPixel(src_c, dst_c, src_c.getAlpha());
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dst->setPixel(dst_x, dst_y, dst_c);
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}
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}
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