1 /* 2 * Copyright 2017 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkGaussFilter_DEFINED 9 #define SkGaussFilter_DEFINED 10 11 #include <cstddef> 12 13 // Define gaussian filters for values of sigma < 2. Produce values good to 1 part in 1,000,000. 14 // Gaussian produces values as defined in the SVG 1.1 spec: 15 // https://www.w3.org/TR/SVG/filters.html#feGaussianBlurElement 16 // Bessel produces values as defined in "Scale-Space for Discrete Signals" by Tony Lindeberg 17 class SkGaussFilter { 18 public: 19 static constexpr int kGaussArrayMax = 6; 20 enum class Type : bool { 21 Gaussian, 22 Bessel 23 }; 24 25 // Type selects which method is used to calculate the gaussian factors. 26 SkGaussFilter(double sigma, Type type); 27 28 size_t size() const { return fN; } 29 int radius() const { return fN - 1; } 30 int width() const { return 2 * this->radius() + 1; } 31 32 // Allow a filter to be used in a C++ ranged-for loop. 33 const double* begin() const { return &fBasis[0]; } 34 const double* end() const { return &fBasis[fN]; } 35 36 private: 37 double fBasis[kGaussArrayMax]; 38 int fN; 39 }; 40 41 #endif // SkGaussFilter_DEFINED 42
