Index: skia/ext/convolver.h |
diff --git a/skia/ext/convolver.h b/skia/ext/convolver.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..37349ae1a2c7773b7cf018f341083a87fa491fbe |
--- /dev/null |
+++ b/skia/ext/convolver.h |
@@ -0,0 +1,235 @@ |
+// 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 <cmath> |
+#include <vector> |
+ |
+#include "base/basictypes.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) && !defined(OS_IOS) |
+#define SIMD_SSE2 1 |
+#define SIMD_PADDING 8 // 8 * int16 |
+#endif |
+ |
+#if defined(ARCH_CPU_MIPS_FAMILY) && defined(__mips_dsp) && \ |
+ (__mips_dsp_rev >= 2) |
+#define SIMD_MIPS_DSPR2 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_ |