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Unified Diff: skia/ext/convolver.h

Issue 2011713003: Roll skia to 8cc209111876b7c78b5ec577c9221d8ed5e21024 (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 4 years, 7 months ago
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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_
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