/**
* @brief weightFunction computes weight functions for x in [0,1].
* @param x is an input value in [0, 1].
* @param type is the type of the function.
* @return It returns a weight for x.
*/
PIC_INLINE float weightFunction(float x, CRF_WEIGHT type)
{
switch(type) {
case CW_ROBERTSON: {
// w(x) = exp(-4*(x*255 - 127.5)^2/(127.5)^2) = exp(-16.0 * (x - 0.5)^2)
// (according to the paper it should be scaled and shifted s.t. w(0) = w(255) = 0 and w(127.5) = 1)
static const double shift = exp(-4);
static const double scaleDiv = (1.0 - shift);
const double t = x - 0.5;
return float((exp(-16.0 * (t * t) ) - shift) / scaleDiv);
}
break;
case CW_HAT: {
float val = (2.0f * x - 1.0f);
float val_squared = val * val;
float val_quartic = val_squared * val_squared;
return (1.0f - val_quartic * val_quartic * val_quartic);
}
break;
case CW_DEB97: {
static const float Zmin = 0.0f;
static const float Zmax = 1.0f;
static const float tr = (Zmin + Zmax) / 2.0f;
if(x <= tr) {
return x - Zmin;
} else {
return Zmax - x;
}
}
break;
case CW_DEB97p01: {
static const float Zmin = 0.01f;
static const float Zmax = 0.99f;
float tr = (Zmin + Zmax) / 2.0f;
if(x <= tr) {
return CLAMPi(x - Zmin, 0.0f, 1.0f);
} else {
return CLAMPi(Zmax - x, 0.0f, 1.0f);
}
}
break;
default: {
return 1.0f;
}
break;
}
return 1.0f;
}
/**
* @brief convertToLDR
* @param exposure
* @param gammaCor
* @return
*/
Color3 convertToLDR(float exposure = 1.0f, float gammaCor = 2.2f)
{
Color3 ret(x * exposure, y * exposure, z * exposure);
ret.gamma(1.0f / gammaCor);
ret.x = CLAMPi(ret.x, 0.0f, 1.0f);
ret.y = CLAMPi(ret.y, 0.0f, 1.0f);
ret.z = CLAMPi(ret.z, 0.0f, 1.0f);
return ret;
}
/**
* @brief MSE computes the mean square error (MSE) between two HDR images with given exposure and gamma.
* @param ori is the original image.
* @param cmp is the distorted image.
* @param gamma is the encoding gamma.
* @param fstop is the f-stop value of the image.
* @param nBit is the number of bits used for the discretization.
* @return It returns the MSE value between ori and cmp.
*/
PIC_INLINE double MSE(Image *ori, Image *cmp, float gamma = 2.2f, float fstop = 0.0f, int nBit = 8)
{
if(ori == NULL || cmp == NULL) {
return -2.0;
}
if(!ori->isValid() || !cmp->isValid()) {
return -4.0;
}
if(!ori->isSimilarType(cmp)) {
return -1.0;
}
float invGamma = 1.0f / gamma;
float exposure = powf(2.0f, fstop);
int area = ori->width * ori->height;
int size = area * ori->channels;
unsigned long long acc = 0;
int nValues = (1 << nBit) - 1;
float nValuesf = float(nValues);
for(int i = 0; i < size; i++) {
int oriLDR = int(nValuesf * (powf(ori->data[i] * exposure, invGamma)));
int cmpLDR = int(nValuesf * (powf(cmp->data[i] * exposure, invGamma)));
oriLDR = CLAMPi(oriLDR, 0, nValues);
cmpLDR = CLAMPi(cmpLDR, 0, nValues);
int delta = cmpLDR - oriLDR;
acc += delta * delta;
}
return (double(acc) / double(area));
}
/**
* @brief ProcessBBox
* @param dst
* @param src
* @param box
*/
void ProcessBBox(Image *dst, ImageVec src, BBox *box)
{
int tmpChannel = CLAMPi(channel, 0, src[0]->channels);
for(int p = box->z0; p < box->z1; p++) {
for(int j = box->y0; j < box->y1; j++) {
for(int i = box->x0; i < box->x1; i++) {
float *dst_data = (*dst)(i, j, p);
float *data = (*src[0])(i, j, p);
dst_data[0] = data[tmpChannel];
}
}
}
}