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Diffstat (limited to 'gfx/2d/convolver.h')
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diff --git a/gfx/2d/convolver.h b/gfx/2d/convolver.h new file mode 100644 index 000000000..0c4591ac8 --- /dev/null +++ b/gfx/2d/convolver.h @@ -0,0 +1,201 @@ +// 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_ |