void HDR::gsolve(std::vector<std::vector<uchar>>& z, std::vector<float>& g, std::vector<float>& lE)
{
if (z.size() != P || z[0].size() != N)
{
std::stringstream ss;
ss << "Error in HDR::gsolve(): input matrix must be (NxP).\n\tz is of size " << z.size() << " but P=" << P << "\n\tz[0] is of size " << z[0].size() << " but N=" << N;
throw std::exception(ss.str().c_str());
}
int n = 256;
//lapack_int nlines = N*P+n+1, ncols = n+N;
int nlins = N*P+n+1, ncols = n+N;
double* b = new double[nlins];
double** A = new double*[nlins];
for (int k=0; k<nlins; k++)
{
b[k] = 0;
A[k] = new double[ncols];
for (int l=0; l<ncols; l++)
{
A[k][l] = 0;
}
}
// Include the data-fitting equations
int k = 0;
// For all pixel locations
for (int i=0; i<N; i++)
{
// For all images
for (int j=0; j<P; j++)
{
int wij = weight(z[j][i] + 1);
A[k][z[j][i]+1] = wij;
A[k][n+i] = -wij;
b[k] = wij * B[j];
k++;
}
}
// Fix the curve by setting its middle value to 0
A[k][128] = 1;
k++;
// Include the smoothness equations
for (int i=0; i<n-2; i++)
{
A[k][i] = lambda * weight(i+1);
A[k][i+1] = -2.0*lambda*weight(i+1);
A[k][i+2] = lambda * weight(i+1);
k++;
}
// Reshape matrix (in row order) so that it can be used with lapack
double* system = new double[nlins*ncols];
for (int k=0; k<nlins*ncols; k++)
{
int i = k / ncols;
int j = k % ncols;
system[k] = A[i][j];
}
// Solve the system using SVD
int sz = std::min(nlins, ncols);
double* s = new double[sz];
lapack_int rank;
LAPACKE_dgelsd(LAPACK_ROW_MAJOR, nlins, ncols, 1, system, ncols, b, 1, s, -1.0, &rank);
// Log exposure for pixel values 0 through 255
g.resize(n, 0.0);
for (int i=0; i<n; i++)
{
g[i] = (float) b[i];
}
// Log film irradiance for every sample pixel
lE.resize(nlins-n, 0.0);
#ifdef DEBUG
std::cout << "N=" << N << "\nP=" << P << "\nsize of lE=" << nlins-n << std::endl;
#endif
for (int i=0; i<nlins-n; i++)
{
lE[i] = (float) b[n+i];
}
};
template <> inline
int gelsd(const char order, const int K, const int N, const int M, double *A, const int LDA, double *B, const int LDB, double *S, double R, int *RANK)
{
return LAPACKE_dgelsd(order, K, N, M, A, LDA, B, LDB, S, R, RANK);
}