// Copyright (c) 2006-2012 The Chromium Authors. All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions // are met: // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // * Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in // the documentation and/or other materials provided with the // distribution. // * Neither the name of Google, Inc. nor the names of its contributors // may be used to endorse or promote products derived from this // software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS // FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE // COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, // BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS // OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED // AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT // OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF // SUCH DAMAGE. #ifndef SKIA_EXT_CONVOLVER_H_ #define SKIA_EXT_CONVOLVER_H_ #include <cmath> #include <vector> #include "base/basictypes.h" #include "mozilla/Assertions.h" #include "skia/include/core/SkTypes.h" // avoid confusion with Mac OS X's math library (Carbon) #if defined(__APPLE__) #undef FloatToFixed #undef FixedToFloat #endif namespace skia { // Represents a filter in one dimension. Each output pixel has one entry in this // object for the filter values contributing to it. You build up the filter // list by calling AddFilter for each output pixel (in order). // // We do 2-dimensional convolution by first convolving each row by one // ConvolutionFilter1D, then convolving each column by another one. // // Entries are stored in fixed point, shifted left by kShiftBits. class ConvolutionFilter1D { public: typedef short Fixed; // The number of bits that fixed point values are shifted by. enum { kShiftBits = 14 }; ConvolutionFilter1D(); ~ConvolutionFilter1D(); // Convert between floating point and our fixed point representation. static Fixed FloatToFixed(float f) { return static_cast<Fixed>(f * (1 << kShiftBits)); } static unsigned char FixedToChar(Fixed x) { return static_cast<unsigned char>(x >> kShiftBits); } static float FixedToFloat(Fixed x) { // The cast relies on Fixed being a short, implying that on // the platforms we care about all (16) bits will fit into // the mantissa of a (32-bit) float. static_assert(sizeof(Fixed) == 2, "fixed type should fit in float mantissa"); float raw = static_cast<float>(x); return ldexpf(raw, -kShiftBits); } // Returns the maximum pixel span of a filter. int max_filter() const { return max_filter_; } // Returns the number of filters in this filter. This is the dimension of the // output image. int num_values() const { return static_cast<int>(filters_.size()); } // Appends the given list of scaling values for generating a given output // pixel. |filter_offset| is the distance from the edge of the image to where // the scaling factors start. The scaling factors apply to the source pixels // starting from this position, and going for the next |filter_length| pixels. // // You will probably want to make sure your input is normalized (that is, // all entries in |filter_values| sub to one) to prevent affecting the overall // brighness of the image. // // The filter_length must be > 0. // // This version will automatically convert your input to fixed point. void AddFilter(int filter_offset, const float* filter_values, int filter_length); // Same as the above version, but the input is already fixed point. void AddFilter(int filter_offset, const Fixed* filter_values, int filter_length); // Retrieves a filter for the given |value_offset|, a position in the output // image in the direction we're convolving. The offset and length of the // filter values are put into the corresponding out arguments (see AddFilter // above for what these mean), and a pointer to the first scaling factor is // returned. There will be |filter_length| values in this array. inline const Fixed* FilterForValue(int value_offset, int* filter_offset, int* filter_length) const { const FilterInstance& filter = filters_[value_offset]; *filter_offset = filter.offset; *filter_length = filter.length; if (filter.length == 0) { return NULL; } return &filter_values_[filter.data_location]; } inline void PaddingForSIMD(int padding_count) { // Padding |padding_count| of more dummy coefficients after the coefficients // of last filter to prevent SIMD instructions which load 8 or 16 bytes // together to access invalid memory areas. We are not trying to align the // coefficients right now due to the opaqueness of <vector> implementation. // This has to be done after all |AddFilter| calls. for (int i = 0; i < padding_count; ++i) filter_values_.push_back(static_cast<Fixed>(0)); } private: struct FilterInstance { // Offset within filter_values for this instance of the filter. int data_location; // Distance from the left of the filter to the center. IN PIXELS int offset; // Number of values in this filter instance. int length; }; // Stores the information for each filter added to this class. std::vector<FilterInstance> filters_; // We store all the filter values in this flat list, indexed by // |FilterInstance.data_location| to avoid the mallocs required for storing // each one separately. std::vector<Fixed> filter_values_; // The maximum size of any filter we've added. int max_filter_; }; // Does a two-dimensional convolution on the given source image. // // It is assumed the source pixel offsets referenced in the input filters // reference only valid pixels, so the source image size is not required. Each // row of the source image starts |source_byte_row_stride| after the previous // one (this allows you to have rows with some padding at the end). // // The result will be put into the given output buffer. The destination image // size will be xfilter.num_values() * yfilter.num_values() pixels. It will be // in rows of exactly xfilter.num_values() * 4 bytes. // // |source_has_alpha| is a hint that allows us to avoid doing computations on // the alpha channel if the image is opaque. If you don't know, set this to // true and it will work properly, but setting this to false will be a few // percent faster if you know the image is opaque. // // The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order // (this is ARGB when loaded into 32-bit words on a little-endian machine). void BGRAConvolve2D(const unsigned char* source_data, int source_byte_row_stride, bool source_has_alpha, const ConvolutionFilter1D& xfilter, const ConvolutionFilter1D& yfilter, int output_byte_row_stride, unsigned char* output); void ConvolveHorizontally(const unsigned char* src_data, const ConvolutionFilter1D& filter, unsigned char* out_row, bool has_alpha, bool use_sse2); void ConvolveVertically(const ConvolutionFilter1D::Fixed* filter_values, int filter_length, unsigned char* const* source_data_rows, int pixel_width, unsigned char* out_row, bool has_alpha, bool use_sse2); } // namespace skia #endif // SKIA_EXT_CONVOLVER_H_