/* Tonemap operator, tonemaps the hdr image and stores the
* tonemapped image in result. Use the value key as the
* key of the photograph. This function should:
* 1) Calculate the log-average luminance, Lavg
* 2) Calculate the tonemapped image using the equation
* L(x,y) = L_w(x,y) * key / Lavg;
* C_tm(x,y) = L(x,y) / (1 + L(x,y));
* 3) Store those tonemapped values to the result image,
* scaling appropriately.
*/
void tonemap(STHDRImage* hdr, float key, STImage* result) {
float logAverageLuminance = 0;
float delta = 0.001;
for (int i=0;i<hdr->GetWidth();i++)
{
for (int j=0;j<hdr->GetHeight();j++)
{
STColor3f currentPixel = hdr->GetPixel(i, j);
logAverageLuminance += logf(currentPixel.r*0.299 + currentPixel.g*0.587 +currentPixel.b*0.114 + delta);
}
}
logAverageLuminance /= (hdr->GetWidth()*hdr->GetHeight());
logAverageLuminance = expf(logAverageLuminance);
for (int i=0;i<hdr->GetWidth();i++)
{
for (int j=0;j<hdr->GetHeight();j++)
{
STColor3f currentPixel = hdr->GetPixel(i, j);
STColor3f currentPixelScaled = currentPixel * (key/logAverageLuminance);
STColor3f compressedCurrentPixelScaled = currentPixelScaled / (STColor3f(1) + currentPixelScaled);
STColor4ub resultPixel(compressedCurrentPixelScaled);
result->SetPixel(i, j, resultPixel);
}
}
}
Light::Light() {
color = STColor3f(0,0,0);
}
/* Luminance. Applies to color components only. */
float STColor4f::Y() const
{
return STColor3f(*this).Y();
}