/**
Poisson solver based on a multigrig algorithm.
This routine solves a Poisson equation, remap result pixels to [0..1] and returns the solution.
NB: The input image is first stored inside a square image whose size is (2^j + 1)x(2^j + 1) for some integer j,
where j is such that 2^j is the nearest larger dimension corresponding to MAX(image width, image height).
@param Laplacian Laplacian image
@param ncycle Number of cycles in the multigrid algorithm (usually 2 or 3)
@return Returns the solved PDE equations if successful, returns NULL otherwise
*/
FIBITMAP* DLL_CALLCONV
FreeImage_MultigridPoissonSolver(FIBITMAP *Laplacian, int ncycle) {
if(!Laplacian) return NULL;
int width = FreeImage_GetWidth(Laplacian);
int height = FreeImage_GetHeight(Laplacian);
// get nearest larger dimension length that is acceptable by the algorithm
int n = MAX(width, height);
int size = 0;
while((n >>= 1) > 0) size++;
// size must be of the form 2^j + 1 for some integer j
size = 1 + (1 << (size + 1));
// allocate a temporary square image I
FIBITMAP *I = FreeImage_AllocateT(FIT_FLOAT, size, size);
if(!I) return NULL;
// copy Laplacian into I and shift pixels to create a boundary
FreeImage_Paste(I, Laplacian, 1, 1, 255);
// solve the PDE equation
fmg_mglin(I, size, ncycle);
// shift pixels back
FIBITMAP *U = FreeImage_Copy(I, 1, 1, width + 1, height + 1);
FreeImage_Unload(I);
// remap pixels to [0..1]
NormalizeY(U, 0, 1);
// return the integrated image
return U;
}
/**
Apply the Gradient Domain High Dynamic Range Compression to a RGBF image and convert to 24-bit RGB
@param dib Input RGBF / RGB16 image
@param color_saturation Color saturation (s parameter in the paper) in [0.4..0.6]
@param attenuation Atenuation factor (beta parameter in the paper) in [0.8..0.9]
@return Returns a 24-bit RGB image if successful, returns NULL otherwise
*/
FIBITMAP* DLL_CALLCONV
FreeImage_TmoFattal02(FIBITMAP *dib, double color_saturation, double attenuation) {
const float alpha = 0.1F; // parameter alpha = 0.1
const float beta = (float)MAX(0.8, MIN(0.9, attenuation)); // parameter beta = [0.8..0.9]
const float s = (float)MAX(0.4, MIN(0.6, color_saturation));// exponent s controls color saturation = [0.4..0.6]
FIBITMAP *src = NULL;
FIBITMAP *Yin = NULL;
FIBITMAP *Yout = NULL;
FIBITMAP *dst = NULL;
if(!FreeImage_HasPixels(dib)) return NULL;
try {
// convert to RGBF
src = FreeImage_ConvertToRGBF(dib);
if(!src) throw(1);
// get the luminance channel
Yin = ConvertRGBFToY(src);
if(!Yin) throw(1);
// perform the tone mapping
Yout = tmoFattal02(Yin, alpha, beta);
if(!Yout) throw(1);
// clip low and high values and normalize to [0..1]
//NormalizeY(Yout, 0.001F, 0.995F);
NormalizeY(Yout, 0, 1);
// compress the dynamic range
const unsigned width = FreeImage_GetWidth(src);
const unsigned height = FreeImage_GetHeight(src);
const unsigned rgb_pitch = FreeImage_GetPitch(src);
const unsigned y_pitch = FreeImage_GetPitch(Yin);
BYTE *bits = (BYTE*)FreeImage_GetBits(src);
BYTE *bits_yin = (BYTE*)FreeImage_GetBits(Yin);
BYTE *bits_yout = (BYTE*)FreeImage_GetBits(Yout);
for(unsigned y = 0; y < height; y++) {
float *Lin = (float*)bits_yin;
float *Lout = (float*)bits_yout;
float *color = (float*)bits;
for(unsigned x = 0; x < width; x++) {
for(unsigned c = 0; c < 3; c++) {
*color = (Lin[x] > 0) ? pow(*color/Lin[x], s) * Lout[x] : 0;
color++;
}
}
bits += rgb_pitch;
bits_yin += y_pitch;
bits_yout += y_pitch;
}
// not needed anymore
FreeImage_Unload(Yin); Yin = NULL;
FreeImage_Unload(Yout); Yout = NULL;
// clamp image highest values to display white, then convert to 24-bit RGB
dst = ClampConvertRGBFTo24(src);
// clean-up and return
FreeImage_Unload(src); src = NULL;
// copy metadata from src to dst
FreeImage_CloneMetadata(dst, dib);
return dst;
} catch(int) {
if(src) FreeImage_Unload(src);
if(Yin) FreeImage_Unload(Yin);
if(Yout) FreeImage_Unload(Yout);
return NULL;
}
}
