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 // Copyright (c) 2013 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef SKIA_EXT_RECURSIVE_GAUSSIAN_CONVOLUTION_H_ #define SKIA_EXT_RECURSIVE_GAUSSIAN_CONVOLUTION_H_ #include "skia/ext/convolver.h" #include "third_party/skia/include/core/SkSize.h" #include "third_party/skia/include/core/SkTypes.h" namespace skia { // RecursiveFilter, paired with SingleChannelRecursiveGaussianX and // SingleChannelRecursiveGaussianY routines below implement recursive filters as // described in 'Recursive implementation of the Gaussian filter' (Young, Vliet) // (1995). Single-letter variable names mirror exactly the usage in the paper to // ease reading and analysis. class RecursiveFilter { public: enum Order { FUNCTION, FIRST_DERIVATIVE, SECOND_DERIVATIVE }; static float qFromSigma(float sigma); static void computeCoefficients(float q, float b[4]); SK_API RecursiveFilter(float sigma, Order order); Order order() const { return order_; } const float* b() const { return b_; } private: Order order_; float q_; float b_[4]; }; // Applies a gaussian recursive filter given as |filter| to a single channel at // |input_channel_index| to image given in |source_data| along X axis. // The output is placed into |output| into channel |output_channel_index|. SK_API unsigned char SingleChannelRecursiveGaussianX( const unsigned char* source_data, int source_byte_row_stride, int input_channel_index, int input_channel_count, const RecursiveFilter& filter, const SkISize& image_size, unsigned char* output, int output_byte_row_stride, int output_channel_index, int output_channel_count, bool absolute_values); // Applies a gaussian recursive filter along Y axis. SK_API unsigned char SingleChannelRecursiveGaussianY( const unsigned char* source_data, int source_byte_row_stride, int input_channel_index, int input_channel_count, const RecursiveFilter& filter, const SkISize& image_size, unsigned char* output, int output_byte_row_stride, int output_channel_index, int output_channel_count, bool absolute_values); } // namespace skia #endif // SKIA_EXT_RECURSIVE_GAUSSIAN_CONVOLUTION_H_