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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#ifndef MOZILLA_GFX_BLUR_H_
#define MOZILLA_GFX_BLUR_H_
#include "mozilla/gfx/Rect.h"
#include "mozilla/gfx/Point.h"
#include "mozilla/CheckedInt.h"
namespace mozilla {
namespace gfx {
#ifdef _MSC_VER
# pragma warning(disable : 4251)
#endif
/**
* Implementation of a triple box blur approximation of a Gaussian blur.
*
* A Gaussian blur is good for blurring because, when done independently
* in the horizontal and vertical directions, it matches the result that
* would be obtained using a different (rotated) set of axes. A triple
* box blur is a very close approximation of a Gaussian.
*
* This is a "service" class; the constructors set up all the information
* based on the values and compute the minimum size for an 8-bit alpha
* channel context.
* The callers are responsible for creating and managing the backing surface
* and passing the pointer to the data to the Blur() method. This class does
* not retain the pointer to the data outside of the Blur() call.
*
* A spread N makes each output pixel the maximum value of all source
* pixels within a square of side length 2N+1 centered on the output pixel.
*/
class GFX2D_API AlphaBoxBlur final {
public:
/** Constructs a box blur and computes the backing surface size.
*
* @param aRect The coordinates of the surface to create in device units.
*
* @param aBlurRadius The blur radius in pixels. This is the radius of the
* entire (triple) kernel function. Each individual box blur has radius
* approximately 1/3 this value, or diameter approximately 2/3 this value.
* This parameter should nearly always be computed using
* CalculateBlurRadius, below.
*
* @param aDirtyRect A pointer to a dirty rect, measured in device units, if
* available. This will be used for optimizing the blur operation. It is
* safe to pass nullptr here.
*
* @param aSkipRect A pointer to a rect, measured in device units, that
* represents an area where blurring is unnecessary and shouldn't be done
* for speed reasons. It is safe to pass nullptr here.
*/
AlphaBoxBlur(const Rect& aRect, const IntSize& aSpreadRadius,
const IntSize& aBlurRadius, const Rect* aDirtyRect,
const Rect* aSkipRect);
AlphaBoxBlur(const Rect& aRect, int32_t aStride, float aSigmaX,
float aSigmaY);
AlphaBoxBlur();
void Init(const Rect& aRect, const IntSize& aSpreadRadius,
const IntSize& aBlurRadius, const Rect* aDirtyRect,
const Rect* aSkipRect);
~AlphaBoxBlur();
/**
* Return the size, in pixels, of the 8-bit alpha surface we'd use.
*/
IntSize GetSize() const;
/**
* Return the stride, in bytes, of the 8-bit alpha surface we'd use.
*/
int32_t GetStride() const;
/**
* Returns the device-space rectangle the 8-bit alpha surface covers.
*/
IntRect GetRect() const;
/**
* Return a pointer to a dirty rect, as passed in to the constructor, or
* nullptr if none was passed in.
*/
Rect* GetDirtyRect();
/**
* Return the spread radius, in pixels.
*/
IntSize GetSpreadRadius() const { return mSpreadRadius; }
/**
* Return the blur radius, in pixels.
*/
IntSize GetBlurRadius() const { return mBlurRadius; }
/**
* Return the minimum buffer size that should be given to Blur() method. If
* zero, the class is not properly setup for blurring. Note that this
* includes the extra three bytes on top of the stride*width, where something
* like gfxImageSurface::GetDataSize() would report without it, even if it
* happens to have the extra bytes.
*/
size_t GetSurfaceAllocationSize() const;
/**
* Perform the blur in-place on the surface backed by specified 8-bit
* alpha surface data. The size must be at least that returned by
* GetSurfaceAllocationSize() or bad things will happen.
*/
void Blur(uint8_t* aData) const;
/**
* Calculates a blur radius that, when used with box blur, approximates a
* Gaussian blur with the given standard deviation. The result of this
* function should be used as the aBlurRadius parameter to AlphaBoxBlur's
* constructor, above.
*/
static IntSize CalculateBlurRadius(const Point& aStandardDeviation);
static Float CalculateBlurSigma(int32_t aBlurRadius);
private:
void BoxBlur_C(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
int32_t aTopLobe, int32_t aBottomLobe,
uint32_t* aIntegralImage, size_t aIntegralImageStride) const;
void BoxBlur_SSE2(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
int32_t aTopLobe, int32_t aBottomLobe,
uint32_t* aIntegralImage,
size_t aIntegralImageStride) const;
void BoxBlur_NEON(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
int32_t aTopLobe, int32_t aBottomLobe,
uint32_t* aIntegralImage,
size_t aIntegralImageStride) const;
#ifdef _MIPS_ARCH_LOONGSON3A
void BoxBlur_LS3(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
int32_t aTopLobe, int32_t aBottomLobe,
uint32_t* aIntegralImage, size_t aIntegralImageStride) const;
#endif
static CheckedInt<int32_t> RoundUpToMultipleOf4(int32_t aVal);
/**
* A rect indicating the area where blurring is unnecessary, and the blur
* algorithm should skip over it.
*
* This is guaranteed to be 4-pixel aligned in the x axis.
*/
IntRect mSkipRect;
/**
* The device-space rectangle the the backing 8-bit alpha surface covers.
*/
IntRect mRect;
/**
* A copy of the dirty rect passed to the constructor. This will only be valid
* if mHasDirtyRect is true.
*/
Rect mDirtyRect;
/**
* The spread radius, in pixels.
*/
IntSize mSpreadRadius;
/**
* The blur radius, in pixels.
*/
IntSize mBlurRadius;
/**
* The stride of the data passed to Blur()
*/
int32_t mStride;
/**
* The minimum size of the buffer needed for the Blur() operation.
*/
size_t mSurfaceAllocationSize;
/**
* Whether mDirtyRect contains valid data.
*/
bool mHasDirtyRect;
};
} // namespace gfx
} // namespace mozilla
#endif /* MOZILLA_GFX_BLUR_H_ */