gecko/gfx/thebes/gfxBlur.h

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* 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 GFX_BLUR_H
#define GFX_BLUR_H
#include "gfxTypes.h"
#include "nsSize.h"
#include "nsAutoPtr.h"
#include "gfxPoint.h"
class gfxContext;
class gfxImageSurface;
struct gfxRect;
namespace mozilla {
namespace gfx {
class AlphaBoxBlur;
}
}
/**
Change the blur radius for -moz-box-shadow and text-shadow to match what is specified in css3-background, and the blur radius for canvas to follow what is specified in HTML5. (Bug 590039) r=roc a2.0=blocking2.0:beta6 This fixes the multiplication by 1.5 in gfxAlphaBoxBlur::CalculateBlurRadius (originally added in changeset ce9f05b57b95 for bug 467518) to work correctly. It was previously a multiplication by 1 due to integer division. CalculateBlurRadius previously multiplied by 1.880; it now multiplies by 2.820. This changes canvas shadow handling to multiply shadowBlur by 2 before taking its square root, as described in the spec. This means that canvas shadow blurs 8px or smaller are 1.5 times larger than they were previously (due to the CalculateBlurRadius change), and canvas shadow blurs larger than 8px are 2.121 times larger than they were previously (due to the CalculateBlurRadius change *and* the additional factor of sqrt(2)). This changes text-shadow and -moz-box-shadow handling to use CalculateBlurRadius on half of the value given instead of passing the value through directly. This means that text-shadow and box-shadow blurs are multiplied by 1.410 relative to their old sizes. It also means that we round rather than floor, so that the effect that used to be drawn by a blur in the range 1px to 1.99px is now drawn by a blur anywhere in the range 0.36px to 1.05px, the effect that used to be drawn by a blur in the range 2px to 2.99px is now drawn by a blur anywhere in the range 1.06px to 1.77px, what used to be a drawn by a blur in the range 3px to 3.99px is now drawn by a blur anywhere in the range 1.78px to 2.47px, etc.
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* 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.
*
* Creates an 8-bit alpha channel context for callers to draw in,
* spreads the contents of that context, blurs the contents, and applies
* it as an alpha mask on a different existing context.
*
* 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.
*
* A temporary surface is created in the Init function. The caller then draws
* any desired content onto the context acquired through GetContext, and lastly
* calls Paint to apply the blurred content as an alpha mask.
*/
class gfxAlphaBoxBlur
{
public:
gfxAlphaBoxBlur();
~gfxAlphaBoxBlur();
/**
* Constructs a box blur and initializes the temporary surface.
* @param aRect The coordinates of the surface to create in device units.
*
Change the blur radius for -moz-box-shadow and text-shadow to match what is specified in css3-background, and the blur radius for canvas to follow what is specified in HTML5. (Bug 590039) r=roc a2.0=blocking2.0:beta6 This fixes the multiplication by 1.5 in gfxAlphaBoxBlur::CalculateBlurRadius (originally added in changeset ce9f05b57b95 for bug 467518) to work correctly. It was previously a multiplication by 1 due to integer division. CalculateBlurRadius previously multiplied by 1.880; it now multiplies by 2.820. This changes canvas shadow handling to multiply shadowBlur by 2 before taking its square root, as described in the spec. This means that canvas shadow blurs 8px or smaller are 1.5 times larger than they were previously (due to the CalculateBlurRadius change), and canvas shadow blurs larger than 8px are 2.121 times larger than they were previously (due to the CalculateBlurRadius change *and* the additional factor of sqrt(2)). This changes text-shadow and -moz-box-shadow handling to use CalculateBlurRadius on half of the value given instead of passing the value through directly. This means that text-shadow and box-shadow blurs are multiplied by 1.410 relative to their old sizes. It also means that we round rather than floor, so that the effect that used to be drawn by a blur in the range 1px to 1.99px is now drawn by a blur anywhere in the range 0.36px to 1.05px, the effect that used to be drawn by a blur in the range 2px to 2.99px is now drawn by a blur anywhere in the range 1.06px to 1.77px, what used to be a drawn by a blur in the range 3px to 3.99px is now drawn by a blur anywhere in the range 1.78px to 2.47px, etc.
2010-09-11 09:27:12 -07:00
* @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.
*/
gfxContext* Init(const gfxRect& aRect,
const gfxIntSize& aSpreadRadius,
const gfxIntSize& aBlurRadius,
const gfxRect* aDirtyRect,
const gfxRect* aSkipRect);
/**
* Returns the context that should be drawn to supply the alpha mask to be
* blurred. If the returned surface is null, then there was an error in
* its creation.
*/
gfxContext* GetContext()
{
return mContext;
}
/**
* Does the actual blurring/spreading and mask applying. Users of this
* object must have drawn whatever they want to be blurred onto the internal
* gfxContext returned by GetContext before calling this.
*
* @param aDestinationCtx The graphics context on which to apply the
* blurred mask.
*/
void Paint(gfxContext* aDestinationCtx);
/**
* Calculates a blur radius that, when used with box blur, approximates
Change the blur radius for -moz-box-shadow and text-shadow to match what is specified in css3-background, and the blur radius for canvas to follow what is specified in HTML5. (Bug 590039) r=roc a2.0=blocking2.0:beta6 This fixes the multiplication by 1.5 in gfxAlphaBoxBlur::CalculateBlurRadius (originally added in changeset ce9f05b57b95 for bug 467518) to work correctly. It was previously a multiplication by 1 due to integer division. CalculateBlurRadius previously multiplied by 1.880; it now multiplies by 2.820. This changes canvas shadow handling to multiply shadowBlur by 2 before taking its square root, as described in the spec. This means that canvas shadow blurs 8px or smaller are 1.5 times larger than they were previously (due to the CalculateBlurRadius change), and canvas shadow blurs larger than 8px are 2.121 times larger than they were previously (due to the CalculateBlurRadius change *and* the additional factor of sqrt(2)). This changes text-shadow and -moz-box-shadow handling to use CalculateBlurRadius on half of the value given instead of passing the value through directly. This means that text-shadow and box-shadow blurs are multiplied by 1.410 relative to their old sizes. It also means that we round rather than floor, so that the effect that used to be drawn by a blur in the range 1px to 1.99px is now drawn by a blur anywhere in the range 0.36px to 1.05px, the effect that used to be drawn by a blur in the range 2px to 2.99px is now drawn by a blur anywhere in the range 1.06px to 1.77px, what used to be a drawn by a blur in the range 3px to 3.99px is now drawn by a blur anywhere in the range 1.78px to 2.47px, etc.
2010-09-11 09:27:12 -07:00
* a Gaussian blur with the given standard deviation. The result of
* this function should be used as the aBlurRadius parameter to Init,
* above.
*/
static gfxIntSize CalculateBlurRadius(const gfxPoint& aStandardDeviation);
protected:
/**
* The context of the temporary alpha surface.
*/
nsRefPtr<gfxContext> mContext;
/**
* The temporary alpha surface.
*/
nsRefPtr<gfxImageSurface> mImageSurface;
/**
* The object that actually does the blurring for us.
*/
mozilla::gfx::AlphaBoxBlur *mBlur;
};
#endif /* GFX_BLUR_H */