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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkBlurMaskFilter_DEFINED
#define SkBlurMaskFilter_DEFINED
#include <algorithm>
#include <memory>
#include "SkMask.h"
#include "SkTypes.h"
// Implement a single channel Gaussian blur. The specifics for implementation are taken from:
// https://drafts.fxtf.org/filters/#feGaussianBlurElement
class SkMaskBlurFilter {
public:
// Given a filter specified by sigma, generate various quantities.
class FilterInfo {
public:
explicit FilterInfo(double sigma);
// The final weight to divide by given a box size calculated from sigma accumulated for
// all three passes. For example, if the box size is 5, then the final weight for all
// three passes is 5^3 or 125.
uint64_t weight() const;
// The distance between the first value of the dst and the first value of the src.
uint32_t borderSize() const;
// The size of the box filter.
size_t diameter(uint8_t) const;
// A factor used to simulate division using multiplication and shift.
uint64_t scaledWeight() const;
private:
const uint32_t fFilterWindow;
const uint64_t fScaledWeight;
};
// Create an object suitable for filtering an SkMask using a filter with width sigmaW and
// height sigmaH.
SkMaskBlurFilter(double sigmaW, double sigmaH);
// Given a src SkMask, generate dst SkMask returning the border width and height.
SkIPoint blur(const SkMask& src, SkMask* dst) const;
private:
size_t bufferSize(uint8_t bufferPass) const;
void blurOneScan(FilterInfo gen,
const uint8_t* src, size_t srcStride, const uint8_t* srcEnd,
uint8_t* dst, size_t dstStride, uint8_t* dstEnd) const;
const FilterInfo fInfoW,
fInfoH;
std::unique_ptr<uint32_t[]> fBuffer0,
fBuffer1,
fBuffer2;
};
#endif // SkBlurMaskFilter_DEFINED
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