#include <Eigen/Sparse>
#include <vector>
#include <QImage>
void insertCoefficient(int id, int i, int j, double w, std::vector<T>& coeffs,
{
int n = int(boundary.size());
int id1 = i+j*n;
if(i==-1 || i==n) b(id) -= w * boundary(j);
else if(j==-1 || j==n) b(id) -= w * boundary(i);
else coeffs.push_back(T(id,id1,w));
}
{
Eigen::ArrayXd boundary = Eigen::ArrayXd::LinSpaced(n, 0,M_PI).sin().pow(2);
for(int j=0; j<n; ++j)
{
for(int i=0; i<n; ++i)
{
int id = i+j*n;
insertCoefficient(id, i-1,j, -1, coefficients, b, boundary);
insertCoefficient(id, i+1,j, -1, coefficients, b, boundary);
insertCoefficient(id, i,j-1, -1, coefficients, b, boundary);
insertCoefficient(id, i,j+1, -1, coefficients, b, boundary);
insertCoefficient(id, i,j, 4, coefficients, b, boundary);
}
}
}
{
QImage img(bits.
data(), n,n,QImage::Format_Indexed8);
img.setColorCount(256);
for(int i=0;i<256;i++) img.setColor(i,qRgb(i,i,i));
img.save(filename);
}
General-purpose arrays with easy API for coefficient-wise operations.
Definition: Array.h:47
The matrix class, also used for vectors and row-vectors.
Definition: Matrix.h:180
Derived & setZero(Index size)
Definition: CwiseNullaryOp.h:562
const Scalar * data() const
Definition: PlainObjectBase.h:247
A versatible sparse matrix representation.
Definition: SparseMatrix.h:98
A small structure to hold a non zero as a triplet (i,j,value).
Definition: SparseUtil.h:163