1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/thebes/gfxBlur.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,151 @@
1.4 +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
1.5 + * This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef GFX_BLUR_H
1.10 +#define GFX_BLUR_H
1.11 +
1.12 +#include "gfxTypes.h"
1.13 +#include "nsSize.h"
1.14 +#include "nsAutoPtr.h"
1.15 +#include "gfxPoint.h"
1.16 +#include "mozilla/RefPtr.h"
1.17 +
1.18 +class gfxContext;
1.19 +struct gfxRect;
1.20 +struct gfxRGBA;
1.21 +class gfxCornerSizes;
1.22 +class gfxMatrix;
1.23 +
1.24 +namespace mozilla {
1.25 + namespace gfx {
1.26 + class AlphaBoxBlur;
1.27 + class SourceSurface;
1.28 + class DrawTarget;
1.29 + }
1.30 +}
1.31 +
1.32 +/**
1.33 + * Implementation of a triple box blur approximation of a Gaussian blur.
1.34 + *
1.35 + * A Gaussian blur is good for blurring because, when done independently
1.36 + * in the horizontal and vertical directions, it matches the result that
1.37 + * would be obtained using a different (rotated) set of axes. A triple
1.38 + * box blur is a very close approximation of a Gaussian.
1.39 + *
1.40 + * Creates an 8-bit alpha channel context for callers to draw in,
1.41 + * spreads the contents of that context, blurs the contents, and applies
1.42 + * it as an alpha mask on a different existing context.
1.43 + *
1.44 + * A spread N makes each output pixel the maximum value of all source
1.45 + * pixels within a square of side length 2N+1 centered on the output pixel.
1.46 + *
1.47 + * A temporary surface is created in the Init function. The caller then draws
1.48 + * any desired content onto the context acquired through GetContext, and lastly
1.49 + * calls Paint to apply the blurred content as an alpha mask.
1.50 + */
1.51 +class gfxAlphaBoxBlur
1.52 +{
1.53 +public:
1.54 + gfxAlphaBoxBlur();
1.55 +
1.56 + ~gfxAlphaBoxBlur();
1.57 +
1.58 + /**
1.59 + * Constructs a box blur and initializes the temporary surface.
1.60 + * @param aRect The coordinates of the surface to create in device units.
1.61 + *
1.62 + * @param aBlurRadius The blur radius in pixels. This is the radius of
1.63 + * the entire (triple) kernel function. Each individual box blur has
1.64 + * radius approximately 1/3 this value, or diameter approximately 2/3
1.65 + * this value. This parameter should nearly always be computed using
1.66 + * CalculateBlurRadius, below.
1.67 + *
1.68 + * @param aDirtyRect A pointer to a dirty rect, measured in device units,
1.69 + * if available. This will be used for optimizing the blur operation. It
1.70 + * is safe to pass nullptr here.
1.71 + *
1.72 + * @param aSkipRect A pointer to a rect, measured in device units, that
1.73 + * represents an area where blurring is unnecessary and shouldn't be done
1.74 + * for speed reasons. It is safe to pass nullptr here.
1.75 + */
1.76 + gfxContext* Init(const gfxRect& aRect,
1.77 + const gfxIntSize& aSpreadRadius,
1.78 + const gfxIntSize& aBlurRadius,
1.79 + const gfxRect* aDirtyRect,
1.80 + const gfxRect* aSkipRect);
1.81 +
1.82 + /**
1.83 + * Returns the context that should be drawn to supply the alpha mask to be
1.84 + * blurred. If the returned surface is null, then there was an error in
1.85 + * its creation.
1.86 + */
1.87 + gfxContext* GetContext()
1.88 + {
1.89 + return mContext;
1.90 + }
1.91 +
1.92 + /**
1.93 + * Does the actual blurring/spreading and mask applying. Users of this
1.94 + * object must have drawn whatever they want to be blurred onto the internal
1.95 + * gfxContext returned by GetContext before calling this.
1.96 + *
1.97 + * @param aDestinationCtx The graphics context on which to apply the
1.98 + * blurred mask.
1.99 + */
1.100 + void Paint(gfxContext* aDestinationCtx);
1.101 +
1.102 + /**
1.103 + * Calculates a blur radius that, when used with box blur, approximates
1.104 + * a Gaussian blur with the given standard deviation. The result of
1.105 + * this function should be used as the aBlurRadius parameter to Init,
1.106 + * above.
1.107 + */
1.108 + static gfxIntSize CalculateBlurRadius(const gfxPoint& aStandardDeviation);
1.109 +
1.110 + /**
1.111 + * Blurs a coloured rectangle onto aDestinationCtx. This is equivalent
1.112 + * to calling Init(), drawing a rectangle onto the returned surface
1.113 + * and then calling Paint, but may let us optimize better in the
1.114 + * backend.
1.115 + *
1.116 + * @param aDestinationCtx The destination to blur to.
1.117 + * @param aRect The rectangle to blur in device pixels.
1.118 + * @param aCornerRadii Corner radii for aRect, if it is a rounded
1.119 + * rectangle.
1.120 + * @param aBlurRadius The standard deviation of the blur.
1.121 + * @param aShadowColor The color to draw the blurred shadow.
1.122 + * @param aDirtyRect An area in device pixels that is dirty and needs
1.123 + * to be redrawn.
1.124 + * @param aSkipRect An area in device pixels to avoid blurring over,
1.125 + * to prevent unnecessary work.
1.126 + */
1.127 + static void BlurRectangle(gfxContext *aDestinationCtx,
1.128 + const gfxRect& aRect,
1.129 + gfxCornerSizes* aCornerRadii,
1.130 + const gfxPoint& aBlurStdDev,
1.131 + const gfxRGBA& aShadowColor,
1.132 + const gfxRect& aDirtyRect,
1.133 + const gfxRect& aSkipRect);
1.134 +
1.135 +
1.136 +
1.137 +protected:
1.138 + /**
1.139 + * The context of the temporary alpha surface.
1.140 + */
1.141 + nsRefPtr<gfxContext> mContext;
1.142 +
1.143 + /**
1.144 + * The temporary alpha surface.
1.145 + */
1.146 + nsAutoArrayPtr<unsigned char> mData;
1.147 +
1.148 + /**
1.149 + * The object that actually does the blurring for us.
1.150 + */
1.151 + mozilla::gfx::AlphaBoxBlur *mBlur;
1.152 +};
1.153 +
1.154 +#endif /* GFX_BLUR_H */
