gecko-dev/gfx/thebes/gfxBlur.h
L. David Baron d022f13c66 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

163 lines
5.9 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is gfx thebes code.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2008
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Eric Butler <zantifon@gmail.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
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* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef GFX_BLUR_H
#define GFX_BLUR_H
#include "gfxContext.h"
#include "gfxImageSurface.h"
#include "gfxTypes.h"
#include "gfxThebesUtils.h"
/**
* 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 THEBES_API 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.
*
* @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 NULL 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 NULL 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;
}
/**
* Premultiplies the image by the given alpha.
*/
void PremultiplyAlpha(gfxFloat alpha);
/**
* 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, const gfxPoint& offset = gfxPoint(0.0, 0.0));
/**
* 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 Init,
* above.
*/
static gfxIntSize CalculateBlurRadius(const gfxPoint& aStandardDeviation);
protected:
/**
* The spread radius, in pixels.
*/
gfxIntSize mSpreadRadius;
/**
* The blur radius, in pixels.
*/
gfxIntSize mBlurRadius;
/**
* The context of the temporary alpha surface.
*/
nsRefPtr<gfxContext> mContext;
/**
* The temporary alpha surface.
*/
nsRefPtr<gfxImageSurface> mImageSurface;
/**
* A copy of the dirty rect passed to Init(). This will only be valid if
* mHasDirtyRect is TRUE.
*/
gfxRect mDirtyRect;
/**
* A rect indicating the area where blurring is unnecessary, and the blur
* algorithm should skip over it.
*/
nsIntRect mSkipRect;
PRPackedBool mHasDirtyRect;
};
#endif /* GFX_BLUR_H */