Narayan Kamath | c981c48 | 2012-11-02 10:59:05 +0000 | [diff] [blame] | 1 | #include <Eigen/Sparse> |
| 2 | #include <vector> |
| 3 | #include <QImage> |
| 4 | |
| 5 | typedef Eigen::SparseMatrix<double> SpMat; // declares a column-major sparse matrix type of double |
| 6 | typedef Eigen::Triplet<double> T; |
| 7 | |
| 8 | void insertCoefficient(int id, int i, int j, double w, std::vector<T>& coeffs, |
| 9 | Eigen::VectorXd& b, const Eigen::VectorXd& boundary) |
| 10 | { |
| 11 | int n = boundary.size(); |
| 12 | int id1 = i+j*n; |
| 13 | |
Carlos Hernandez | 7faaa9f | 2014-08-05 17:53:32 -0700 | [diff] [blame] | 14 | if(i==-1 || i==n) b(id) -= w * boundary(j); // constrained coefficient |
| 15 | else if(j==-1 || j==n) b(id) -= w * boundary(i); // constrained coefficient |
Narayan Kamath | c981c48 | 2012-11-02 10:59:05 +0000 | [diff] [blame] | 16 | else coeffs.push_back(T(id,id1,w)); // unknown coefficient |
| 17 | } |
| 18 | |
| 19 | void buildProblem(std::vector<T>& coefficients, Eigen::VectorXd& b, int n) |
| 20 | { |
| 21 | b.setZero(); |
| 22 | Eigen::ArrayXd boundary = Eigen::ArrayXd::LinSpaced(n, 0,M_PI).sin().pow(2); |
| 23 | for(int j=0; j<n; ++j) |
| 24 | { |
| 25 | for(int i=0; i<n; ++i) |
| 26 | { |
| 27 | int id = i+j*n; |
| 28 | insertCoefficient(id, i-1,j, -1, coefficients, b, boundary); |
| 29 | insertCoefficient(id, i+1,j, -1, coefficients, b, boundary); |
| 30 | insertCoefficient(id, i,j-1, -1, coefficients, b, boundary); |
| 31 | insertCoefficient(id, i,j+1, -1, coefficients, b, boundary); |
| 32 | insertCoefficient(id, i,j, 4, coefficients, b, boundary); |
| 33 | } |
| 34 | } |
| 35 | } |
| 36 | |
| 37 | void saveAsBitmap(const Eigen::VectorXd& x, int n, const char* filename) |
| 38 | { |
| 39 | Eigen::Array<unsigned char,Eigen::Dynamic,Eigen::Dynamic> bits = (x*255).cast<unsigned char>(); |
| 40 | QImage img(bits.data(), n,n,QImage::Format_Indexed8); |
| 41 | img.setColorCount(256); |
| 42 | for(int i=0;i<256;i++) img.setColor(i,qRgb(i,i,i)); |
| 43 | img.save(filename); |
| 44 | } |