michael@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef GFX_BLUR_H
michael@0: #define GFX_BLUR_H
michael@0: 
michael@0: #include "gfxTypes.h"
michael@0: #include "nsSize.h"
michael@0: #include "nsAutoPtr.h"
michael@0: #include "gfxPoint.h"
michael@0: #include "mozilla/RefPtr.h"
michael@0: 
michael@0: class gfxContext;
michael@0: struct gfxRect;
michael@0: struct gfxRGBA;
michael@0: class gfxCornerSizes;
michael@0: class gfxMatrix;
michael@0: 
michael@0: namespace mozilla {
michael@0:   namespace gfx {
michael@0:     class AlphaBoxBlur;
michael@0:     class SourceSurface;
michael@0:     class DrawTarget;
michael@0:   }
michael@0: }
michael@0: 
michael@0: /**
michael@0:  * Implementation of a triple box blur approximation of a Gaussian blur.
michael@0:  *
michael@0:  * A Gaussian blur is good for blurring because, when done independently
michael@0:  * in the horizontal and vertical directions, it matches the result that
michael@0:  * would be obtained using a different (rotated) set of axes.  A triple
michael@0:  * box blur is a very close approximation of a Gaussian.
michael@0:  *
michael@0:  * Creates an 8-bit alpha channel context for callers to draw in,
michael@0:  * spreads the contents of that context, blurs the contents, and applies
michael@0:  * it as an alpha mask on a different existing context.
michael@0:  * 
michael@0:  * A spread N makes each output pixel the maximum value of all source
michael@0:  * pixels within a square of side length 2N+1 centered on the output pixel.
michael@0:  * 
michael@0:  * A temporary surface is created in the Init function. The caller then draws
michael@0:  * any desired content onto the context acquired through GetContext, and lastly
michael@0:  * calls Paint to apply the blurred content as an alpha mask.
michael@0:  */
michael@0: class gfxAlphaBoxBlur
michael@0: {
michael@0: public:
michael@0:     gfxAlphaBoxBlur();
michael@0: 
michael@0:     ~gfxAlphaBoxBlur();
michael@0: 
michael@0:     /**
michael@0:      * Constructs a box blur and initializes the temporary surface.
michael@0:      * @param aRect The coordinates of the surface to create in device units.
michael@0:      *
michael@0:      * @param aBlurRadius The blur radius in pixels.  This is the radius of
michael@0:      *   the entire (triple) kernel function.  Each individual box blur has
michael@0:      *   radius approximately 1/3 this value, or diameter approximately 2/3
michael@0:      *   this value.  This parameter should nearly always be computed using
michael@0:      *   CalculateBlurRadius, below.
michael@0:      *
michael@0:      * @param aDirtyRect A pointer to a dirty rect, measured in device units,
michael@0:      *  if available. This will be used for optimizing the blur operation. It
michael@0:      *  is safe to pass nullptr here.
michael@0:      *
michael@0:      * @param aSkipRect A pointer to a rect, measured in device units, that
michael@0:      *  represents an area where blurring is unnecessary and shouldn't be done
michael@0:      *  for speed reasons. It is safe to pass nullptr here.
michael@0:      */
michael@0:     gfxContext* Init(const gfxRect& aRect,
michael@0:                      const gfxIntSize& aSpreadRadius,
michael@0:                      const gfxIntSize& aBlurRadius,
michael@0:                      const gfxRect* aDirtyRect,
michael@0:                      const gfxRect* aSkipRect);
michael@0: 
michael@0:     /**
michael@0:      * Returns the context that should be drawn to supply the alpha mask to be
michael@0:      * blurred. If the returned surface is null, then there was an error in
michael@0:      * its creation.
michael@0:      */
michael@0:     gfxContext* GetContext()
michael@0:     {
michael@0:         return mContext;
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Does the actual blurring/spreading and mask applying. Users of this
michael@0:      * object must have drawn whatever they want to be blurred onto the internal
michael@0:      * gfxContext returned by GetContext before calling this.
michael@0:      *
michael@0:      * @param aDestinationCtx The graphics context on which to apply the
michael@0:      *  blurred mask.
michael@0:      */
michael@0:     void Paint(gfxContext* aDestinationCtx);
michael@0: 
michael@0:     /**
michael@0:      * Calculates a blur radius that, when used with box blur, approximates
michael@0:      * a Gaussian blur with the given standard deviation.  The result of
michael@0:      * this function should be used as the aBlurRadius parameter to Init,
michael@0:      * above.
michael@0:      */
michael@0:     static gfxIntSize CalculateBlurRadius(const gfxPoint& aStandardDeviation);
michael@0: 
michael@0:     /**
michael@0:      * Blurs a coloured rectangle onto aDestinationCtx. This is equivalent
michael@0:      * to calling Init(), drawing a rectangle onto the returned surface
michael@0:      * and then calling Paint, but may let us optimize better in the
michael@0:      * backend.
michael@0:      *
michael@0:      * @param aDestinationCtx      The destination to blur to.
michael@0:      * @param aRect                The rectangle to blur in device pixels.
michael@0:      * @param aCornerRadii         Corner radii for aRect, if it is a rounded
michael@0:      *                             rectangle.
michael@0:      * @param aBlurRadius          The standard deviation of the blur.
michael@0:      * @param aShadowColor         The color to draw the blurred shadow.
michael@0:      * @param aDirtyRect           An area in device pixels that is dirty and needs
michael@0:      *                             to be redrawn.
michael@0:      * @param aSkipRect            An area in device pixels to avoid blurring over,
michael@0:      *                             to prevent unnecessary work.
michael@0:      */
michael@0:     static void BlurRectangle(gfxContext *aDestinationCtx,
michael@0:                               const gfxRect& aRect,
michael@0:                               gfxCornerSizes* aCornerRadii,
michael@0:                               const gfxPoint& aBlurStdDev,
michael@0:                               const gfxRGBA& aShadowColor,
michael@0:                               const gfxRect& aDirtyRect,
michael@0:                               const gfxRect& aSkipRect);
michael@0: 
michael@0: 
michael@0: 
michael@0: protected:
michael@0:     /**
michael@0:      * The context of the temporary alpha surface.
michael@0:      */
michael@0:     nsRefPtr<gfxContext> mContext;
michael@0: 
michael@0:     /**
michael@0:      * The temporary alpha surface.
michael@0:      */
michael@0:     nsAutoArrayPtr<unsigned char> mData;
michael@0: 
michael@0:      /**
michael@0:       * The object that actually does the blurring for us.
michael@0:       */
michael@0:     mozilla::gfx::AlphaBoxBlur *mBlur;
michael@0: };
michael@0: 
michael@0: #endif /* GFX_BLUR_H */