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203 lines
8.2 KiB
C++
203 lines
8.2 KiB
C++
// Copyright (c) 2006-2012 The Chromium Authors. All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in
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// the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google, Inc. nor the names of its contributors
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// may be used to endorse or promote products derived from this
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// software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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// SUCH DAMAGE.
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#ifndef SKIA_EXT_CONVOLVER_H_
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#define SKIA_EXT_CONVOLVER_H_
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#include <cmath>
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#include <vector>
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#include "base/basictypes.h"
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#include "base/cpu.h"
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#include "mozilla/Assertions.h"
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#include "skia/include/core/SkTypes.h"
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// avoid confusion with Mac OS X's math library (Carbon)
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#if defined(__APPLE__)
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#undef FloatToFixed
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#undef FixedToFloat
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#endif
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namespace skia {
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// Represents a filter in one dimension. Each output pixel has one entry in this
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// object for the filter values contributing to it. You build up the filter
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// list by calling AddFilter for each output pixel (in order).
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//
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// We do 2-dimensional convolution by first convolving each row by one
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// ConvolutionFilter1D, then convolving each column by another one.
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//
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// Entries are stored in fixed point, shifted left by kShiftBits.
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class ConvolutionFilter1D {
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public:
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typedef short Fixed;
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// The number of bits that fixed point values are shifted by.
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enum { kShiftBits = 14 };
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ConvolutionFilter1D();
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~ConvolutionFilter1D();
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// Convert between floating point and our fixed point representation.
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static Fixed FloatToFixed(float f) {
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return static_cast<Fixed>(f * (1 << kShiftBits));
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}
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static unsigned char FixedToChar(Fixed x) {
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return static_cast<unsigned char>(x >> kShiftBits);
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}
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static float FixedToFloat(Fixed x) {
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// The cast relies on Fixed being a short, implying that on
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// the platforms we care about all (16) bits will fit into
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// the mantissa of a (32-bit) float.
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static_assert(sizeof(Fixed) == 2,
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"fixed type should fit in float mantissa");
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float raw = static_cast<float>(x);
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return ldexpf(raw, -kShiftBits);
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}
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// Returns the maximum pixel span of a filter.
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int max_filter() const { return max_filter_; }
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// Returns the number of filters in this filter. This is the dimension of the
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// output image.
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int num_values() const { return static_cast<int>(filters_.size()); }
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// Appends the given list of scaling values for generating a given output
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// pixel. |filter_offset| is the distance from the edge of the image to where
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// the scaling factors start. The scaling factors apply to the source pixels
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// starting from this position, and going for the next |filter_length| pixels.
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//
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// You will probably want to make sure your input is normalized (that is,
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// all entries in |filter_values| sub to one) to prevent affecting the overall
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// brighness of the image.
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//
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// The filter_length must be > 0.
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//
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// This version will automatically convert your input to fixed point.
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void AddFilter(int filter_offset,
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const float* filter_values,
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int filter_length);
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// Same as the above version, but the input is already fixed point.
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void AddFilter(int filter_offset,
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const Fixed* filter_values,
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int filter_length);
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// Retrieves a filter for the given |value_offset|, a position in the output
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// image in the direction we're convolving. The offset and length of the
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// filter values are put into the corresponding out arguments (see AddFilter
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// above for what these mean), and a pointer to the first scaling factor is
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// returned. There will be |filter_length| values in this array.
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inline const Fixed* FilterForValue(int value_offset,
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int* filter_offset,
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int* filter_length) const {
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const FilterInstance& filter = filters_[value_offset];
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*filter_offset = filter.offset;
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*filter_length = filter.length;
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if (filter.length == 0) {
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return NULL;
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}
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return &filter_values_[filter.data_location];
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}
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inline void PaddingForSIMD(int padding_count) {
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// Padding |padding_count| of more dummy coefficients after the coefficients
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// of last filter to prevent SIMD instructions which load 8 or 16 bytes
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// together to access invalid memory areas. We are not trying to align the
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// coefficients right now due to the opaqueness of <vector> implementation.
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// This has to be done after all |AddFilter| calls.
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for (int i = 0; i < padding_count; ++i)
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filter_values_.push_back(static_cast<Fixed>(0));
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}
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private:
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struct FilterInstance {
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// Offset within filter_values for this instance of the filter.
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int data_location;
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// Distance from the left of the filter to the center. IN PIXELS
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int offset;
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// Number of values in this filter instance.
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int length;
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};
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// Stores the information for each filter added to this class.
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std::vector<FilterInstance> filters_;
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// We store all the filter values in this flat list, indexed by
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// |FilterInstance.data_location| to avoid the mallocs required for storing
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// each one separately.
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std::vector<Fixed> filter_values_;
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// The maximum size of any filter we've added.
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int max_filter_;
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};
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// Does a two-dimensional convolution on the given source image.
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//
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// It is assumed the source pixel offsets referenced in the input filters
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// reference only valid pixels, so the source image size is not required. Each
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// row of the source image starts |source_byte_row_stride| after the previous
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// one (this allows you to have rows with some padding at the end).
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//
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// The result will be put into the given output buffer. The destination image
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// size will be xfilter.num_values() * yfilter.num_values() pixels. It will be
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// in rows of exactly xfilter.num_values() * 4 bytes.
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//
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// |source_has_alpha| is a hint that allows us to avoid doing computations on
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// the alpha channel if the image is opaque. If you don't know, set this to
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// true and it will work properly, but setting this to false will be a few
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// percent faster if you know the image is opaque.
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//
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// The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order
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// (this is ARGB when loaded into 32-bit words on a little-endian machine).
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void BGRAConvolve2D(const unsigned char* source_data,
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int source_byte_row_stride,
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bool source_has_alpha,
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const ConvolutionFilter1D& xfilter,
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const ConvolutionFilter1D& yfilter,
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int output_byte_row_stride,
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unsigned char* output);
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void ConvolveHorizontally(const unsigned char* src_data,
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const ConvolutionFilter1D& filter,
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unsigned char* out_row,
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bool has_alpha, bool use_sse2);
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void ConvolveVertically(const ConvolutionFilter1D::Fixed* filter_values,
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int filter_length,
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unsigned char* const* source_data_rows,
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int pixel_width, unsigned char* out_row,
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bool has_alpha, bool use_sse2);
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} // namespace skia
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#endif // SKIA_EXT_CONVOLVER_H_
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