/* -*- 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

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#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

{

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;

#ifdef BUILD_ARM_NEON

  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;

#endif

#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.

   */

  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_ */