bicubic_interpolation.hpp

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#pragma once
 
#include <wmtk/function/utils/autodiff.h>
#include <Eigen/Core>
#include <Eigen/Dense>
#include <type_traits>
namespace wmtk::components::adaptive_tessellation::image {
enum class WrappingMode { REPEAT, MIRROR_REPEAT, CLAMP_TO_EDGE };
inline double get_value(float x)
{
    return static_cast<double>(x);
}
inline double get_value(double x)
{
    return x;
}
inline double get_value(
    DScalar2<double, Eigen::Matrix<double, 2, 1>, Eigen::Matrix<double, 2, 2>> x)
{
    return x.getValue();
}
 
inline double get_value(
    DScalar2<double, Eigen::Matrix<double, -1, 1>, Eigen::Matrix<double, -1, -1>> x)
{
    return x.getValue();
}
 
template <class T>
using BicubicVector = Eigen::Matrix<T, 16, 1>;
using BicubicMatrix = Eigen::Matrix<float, 16, 16>;
 
BicubicVector<float> extract_samples(
    const size_t width,
    const size_t height,
    const float* buffer,
    const double xx,
    const double yy,
    const WrappingMode mode_x,
    const WrappingMode mode_y);
 
BicubicMatrix make_samples_to_bicubic_coeffs_operator();
 
const BicubicMatrix& get_bicubic_matrix();
 
template <class T>
std::decay_t<T> eval_bicubic_coeffs(const BicubicVector<float>& coeffs, const T& sx, const T& sy)
{
    using ImageScalar = std::decay_t<T>;
 
    const auto xx = sx - (floor(get_value(sx) - 0.5f) + 0.5f);
    const auto yy = sy - (floor(get_value(sy) - 0.5f) + 0.5f);
    assert(0 <= get_value(xx) && get_value(xx) < 1);
    assert(0 <= get_value(yy) && get_value(yy) < 1);
 
    BicubicVector<ImageScalar> vv;
 
    vv(0) = 1;
    vv(1) = xx;
    vv(2) = xx * xx;
    vv(3) = xx * xx * xx;
 
    vv(4) = yy;
    vv(5) = xx * yy;
    vv(6) = xx * xx * yy;
    vv(7) = xx * xx * xx * yy;
 
    vv(8) = yy * yy;
    vv(9) = xx * yy * yy;
    vv(10) = xx * xx * yy * yy;
    vv(11) = xx * xx * xx * yy * yy;
 
    vv(12) = yy * yy * yy;
    vv(13) = xx * yy * yy * yy;
    vv(14) = xx * xx * yy * yy * yy;
    vv(15) = xx * xx * xx * yy * yy * yy;
 
    return coeffs.cast<ImageScalar>().dot(vv);
}
 
} // namespace wmtk::components::adaptive_tessellation::image