The Tor Browser: comparison gfx/2d/convolver.h

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+// 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 "base/cpu.h"
+#include "mozilla/Assertions.h"
+#include "skia/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,
+bool use_sse2);
+}  // namespace skia
+#endif  // SKIA_EXT_CONVOLVER_H_

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comparison: gfx/2d/convolver.h

gfx/2d/convolver.h