Class LanczosKernelFunc

tensorflow/core/kernels/sampling_kernels.h:68–84

A function object for a Lanczos kernel.

// A function object for a Lanczos kernel.
struct LanczosKernelFunc {
  // Pass 1 for Lanczos1 kernel, 3 for Lanczos3 etc.
  explicit LanczosKernelFunc(float _radius) : radius(_radius) {}
  float operator()(float x) const {
    constexpr float kPI = 3.14159265359;
    x = std::abs(x);
    if (x > radius) return 0.0;
    // Need to special case the limit case of sin(x) / x when x is zero.
    if (x <= 1e-3) {
      return 1.0;
    }
    return radius * std::sin(kPI * x) * std::sin(kPI * x / radius) /
           (kPI * kPI * x * x);
  }
  float Radius() const { return radius; }
  const float radius;
};

struct GaussianKernelFunc {
  static constexpr float kRadiusMultiplier = 3.0f;