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- // Copyright (c) 2012 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_CONVOLVER_H_
- #define SKIA_EXT_CONVOLVER_H_
- #include <stdint.h>
- #include <cmath>
- #include <vector>
- #include "build/build_config.h"
- #include "third_party/skia/include/core/SkSize.h"
- #include "third_party/skia/include/core/SkTypes.h"
- // We can build SSE2 optimized versions for all x86 CPUs
- // except when building for the IOS emulator.
- #if defined(ARCH_CPU_X86_FAMILY) && !BUILDFLAG(IS_IOS)
- #define SIMD_SSE2 1
- #define SIMD_PADDING 8 // 8 * int16_t
- #endif
- #if defined (ARCH_CPU_MIPS_FAMILY) && \
- defined(__mips_dsp) && (__mips_dsp_rev >= 2)
- #define SIMD_MIPS_DSPR2 1
- #endif
- #if defined(ARCH_CPU_ARM_FAMILY) && \
- (defined(__ARM_NEON__) || defined(__ARM_NEON))
- #define SIMD_NEON 1
- #endif
- // 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 };
- SK_API ConvolutionFilter1D();
- SK_API ~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.
- SK_API 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.trimmed_length;
- if (filter.trimmed_length == 0) {
- return NULL;
- }
- return &filter_values_[filter.data_location];
- }
- // Retrieves the filter for the offset 0, presumed to be the one and only.
- // The offset and length of the filter values are put into the corresponding
- // out arguments (see AddFilter). Note that |filter_legth| and
- // |specified_filter_length| may be different if leading/trailing zeros of the
- // original floating point form were clipped.
- // There will be |filter_length| values in the return array.
- // Returns NULL if the filter is 0-length (for instance when all floating
- // point values passed to AddFilter were clipped to 0).
- SK_API const Fixed* GetSingleFilter(int* specified_filter_length,
- int* filter_offset,
- int* filter_length) const;
- inline void PaddingForSIMD() {
- // 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.
- #ifdef SIMD_PADDING
- for (int i = 0; i < SIMD_PADDING; ++i)
- filter_values_.push_back(static_cast<Fixed>(0));
- #endif
- }
- 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 trimmed_length;
- // Filter length as specified. Note that this may be different from
- // 'trimmed_length' if leading/trailing zeros of the original floating
- // point form were clipped differently on each tail.
- 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).
- SK_API 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,
- bool use_simd_if_possible);
- // Does a 1D convolution of the given source image along the X dimension on
- // a single channel of the bitmap.
- //
- // The function uses the same convolution kernel for each pixel. That kernel
- // must be added to |filter| at offset 0. This is a most straightforward
- // implementation of convolution, intended chiefly for development purposes.
- SK_API void SingleChannelConvolveX1D(const unsigned char* source_data,
- int source_byte_row_stride,
- int input_channel_index,
- int input_channel_count,
- const ConvolutionFilter1D& filter,
- const SkISize& image_size,
- unsigned char* output,
- int output_byte_row_stride,
- int output_channel_index,
- int output_channel_count,
- bool absolute_values);
- // Does a 1D convolution of the given source image along the Y dimension on
- // a single channel of the bitmap.
- SK_API void SingleChannelConvolveY1D(const unsigned char* source_data,
- int source_byte_row_stride,
- int input_channel_index,
- int input_channel_count,
- const ConvolutionFilter1D& filter,
- const SkISize& image_size,
- unsigned char* output,
- int output_byte_row_stride,
- int output_channel_index,
- int output_channel_count,
- bool absolute_values);
- // Set up the |filter| instance with a gaussian kernel. |kernel_sigma| is the
- // parameter of gaussian. If |derivative| is true, the kernel will be that of
- // the first derivative. Intended for use with the two routines above.
- SK_API void SetUpGaussianConvolutionKernel(ConvolutionFilter1D* filter,
- float kernel_sigma,
- bool derivative);
- } // namespace skia
- #endif // SKIA_EXT_CONVOLVER_H_
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