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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 "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_