static inline float curve_scalar(
const float x,
const float g,
const float sigma,
const float shadows,
const float highlights,
const float clarity)
{
const float c = x-g;
float val;
// blend in via quadratic bezier
if (c > 2*sigma) val = g + sigma + shadows * (c-sigma);
else if(c < -2*sigma) val = g - sigma + highlights * (c+sigma);
else if(c > 0.0f)
{ // shadow contrast
const float t = CLAMPS(c / (2.0f*sigma), 0.0f, 1.0f);
const float t2 = t * t;
const float mt = 1.0f-t;
val = g + sigma * 2.0f*mt*t + t2*(sigma + sigma*shadows);
}
else
{ // highlight contrast
const float t = CLAMPS(-c / (2.0f*sigma), 0.0f, 1.0f);
const float t2 = t * t;
const float mt = 1.0f-t;
val = g - sigma * 2.0f*mt*t + t2*(- sigma - sigma*highlights);
}
// midtone local contrast
val += clarity * c * dt_fast_expf(-c*c/(2.0*sigma*sigma/3.0f));
return val;
}
static float
color_filter(const float ai, const float bi, const float a, const float b, const float size)
{
return dt_fast_expf(-CLAMPS(((ai-a)*(ai-a) + (bi-b)*(bi-b))/(2.0*size), 0.0f, 1.0f));
}
