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faster sigmoid function to create the contrast mask used in dual demosaic and capture sharpening, #6386 (#6387)

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Ingo Weyrich 2021-12-01 15:01:27 +01:00 committed by GitHub
parent 40827955ca
commit 3567d54b52
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1 changed files with 13 additions and 3 deletions
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16
rtengine/rt_algo.cc
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@ -35,14 +35,24 @@
namespace {
template<typename T>
T calcBlendFactor(T val, T threshold) {
float calcBlendFactor(float val, float threshold) {
// sigmoid function
// result is in ]0;1] range
// inflexion point is at (x, y) (threshold, 0.5)
return 1.f / (1.f + xexpf(16.f - (16.f / threshold) * val));
const float x = -16.f + (16.f / threshold) * val;
return 0.5f * (1.f + x / std::sqrt(1.f + rtengine::SQR(x)));
}
#ifdef __SSE2__
vfloat calcBlendFactor(vfloat val, vfloat threshold) {
// sigmoid function
// result is in ]0;1] range
// inflexion point is at (x, y) (threshold, 0.5)
const vfloat x = -16.f + (16.f / threshold) * val;
return 0.5f * (1.f + x * _mm_rsqrt_ps(1.f + rtengine::SQR(x)));
}
#endif
float tileAverage(const float * const *data, size_t tileY, size_t tileX, size_t tilesize) {
float avg = 0.f;