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texturec: Premultiply alpha in linear space.

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Branimir Karadžić
2018-04-13 17:11:42 -07:00
parent 6bd4ba8fdd
commit 6afba8a0eb
1 changed files with 20 additions and 3 deletions
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23
tools/texturec/texturec.cpp
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@@ -100,6 +100,22 @@ void imageRgba32fNormalize(void* _dst, uint32_t _width, uint32_t _height, uint32
}
}
float toLinear(float _a)
{
const float lo = _a / 12.92f;
const float hi = bx::pow( (_a + 0.055f) / 1.055f, 2.4f);
const float result = bx::lerp(hi, lo, _a <= 0.04045f);
return result;
}
float toGamma(float _a)
{
const float lo = _a * 12.92f;
const float hi = bx::pow(bx::abs(_a), 1.0f/2.4f) * 1.055f - 0.055f;
const float result = bx::lerp(hi, lo, _a <= 0.0031308f);
return result;
}
void imagePremultiplyAlpha(void* _inOut, uint32_t _width, uint32_t _height, uint32_t _depth, bimg::TextureFormat::Enum _format)
{
uint8_t* inOut = (uint8_t*)_inOut;
@@ -119,9 +135,10 @@ void imagePremultiplyAlpha(void* _inOut, uint32_t _width, uint32_t _height, uint
float rgba[4];
unpack(rgba, &inOut[offset]);
rgba[0] *= rgba[3];
rgba[1] *= rgba[3];
rgba[2] *= rgba[3];
const float alpha = rgba[3];
rgba[0] = toGamma(toLinear(rgba[0]) * alpha);
rgba[1] = toGamma(toLinear(rgba[1]) * alpha);
rgba[2] = toGamma(toLinear(rgba[2]) * alpha);
pack(&inOut[offset], rgba);
}
}