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DmitriyKorchemkin/example_bicubic.cc

Created September 16, 2021 17:33
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  1. DmitriyKorchemkin created this gist Sep 16, 2021.
    64 changes: 64 additions & 0 deletions example_bicubic.cc
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    /* Small example of using bicubic interpolation in ceres with autodiff */
    #include <ceres/ceres.h>
    #include <ceres/cubic_interpolation.h>

    #include <cassert>

    using Grid = ceres::Grid2D<double>;
    using Interpolator = ceres::BiCubicInterpolator<Grid>;

    struct Residual {
    template <typename T>
    bool operator()(const T* shift, T* residual) const {
    T x = px + shift[0], y = py + shift[1], v;

    interpolator.Evaluate(y, x, &v);
    *residual = v - val;
    return true;
    }
    Residual(const Interpolator& img, double px, double py, double val)
    : interpolator(img), px(px), py(py), val(val) {}
    static ceres::CostFunction* CreateCost(const Interpolator& interpolator,
    double px, double py, double val) {
    return new ceres::AutoDiffCostFunction<Residual, 1, 2>(
    new Residual(interpolator, px, py, val));
    }
    const Interpolator& interpolator;
    double px, py, val;
    };

    int main() {
    Eigen::Array<double, 6, 7, Eigen::RowMajor> img_data;
    img_data <<
    0., 0., 0., 0., 0., 0., 0.,
    0., 1., 0., 0., 0., 0., 0.,
    0., 0., 0., 0., 0., 0., 0.,
    0., 0., 0., 0., 2., 0., 0.,
    0., 0., 0., 0., 0., 0., 0.,
    0., 0., 0., 0., 0., 0., 0.;

    Grid grid(img_data.data(), 0, img_data.rows(), 0, img_data.cols());
    Interpolator interpolator(grid);

    double shift[2] = {1., 1.};
    ceres::Problem problem;
    problem.AddParameterBlock(shift, 2);

    problem.AddResidualBlock(Residual::CreateCost(interpolator, .5, .5, 1.),
    nullptr, shift);
    problem.AddResidualBlock(Residual::CreateCost(interpolator, 3.5, 2.5, 2.),
    nullptr, shift);

    ceres::Solver::Options options;
    options.linear_solver_type = ceres::DENSE_QR;
    options.minimizer_progress_to_stdout = true;
    ceres::Solver::Summary summary;
    ceres::Solve(options, &problem, &summary);

    std::cout << summary.BriefReport() << "\n" << summary.FullReport()
    << "\nShift: " << shift[0] << ' ' << shift[1] << '\n';

    assert(std::abs(shift[0] - 0.5) < 1e-3);
    assert(std::abs(shift[1] - 0.5) < 1e-3);
    return 0;
    }