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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkImageFilter_DEFINED
#define SkImageFilter_DEFINED
#include "SkFlattenable.h"
class SkBitmap;
class SkDevice;
class SkMatrix;
struct SkPoint;
/**
* Experimental.
*
* Base class for image filters. If one is installed in the paint, then
* all drawing occurs as usual, but it is as if the drawing happened into an
* offscreen (before the xfermode is applied). This offscreen bitmap will
* then be handed to the imagefilter, who in turn creates a new bitmap which
* is what will finally be drawn to the device (using the original xfermode).
*
* THIS SIGNATURE IS TEMPORARY
*
* There are several weaknesses in this function signature:
* 1. Does not expose the destination/target device, so filters that can draw
* directly to it are unable to take advantage of that optimization.
* 2. Does not expose a way to create a "compabitible" image (i.e. gpu -> gpu)
* 3. As with #1, the filter is unable to "read" the dest (which would be slow)
*
* Therefore, we should not create any real dependencies on this API yet -- it
* is being checked in as a check-point so we can explore these and other
* considerations.
*/
class SK_API SkImageFilter : public SkFlattenable {
public:
class Proxy {
public:
virtual SkDevice* createDevice(int width, int height) = 0;
// returns true if the proxy handled the filter itself. if this returns
// false then the filter's code will be called.
virtual bool filterImage(SkImageFilter*, const SkBitmap& src,
const SkMatrix& ctm,
SkBitmap* result, SkIPoint* offset) = 0;
virtual ~Proxy() {};
};
/**
* Request a new (result) image to be created from the src image.
* If the src has no pixels (isNull()) then the request just wants to
* receive the config and width/height of the result.
*
* The matrix is the current matrix on the canvas.
*
* Offset is the amount to translate the resulting image relative to the
* src when it is drawn.
*
* If the result image cannot be created, return false, in which case both
* the result and offset parameters will be ignored by the caller.
*/
bool filterImage(Proxy*, const SkBitmap& src, const SkMatrix& ctm,
SkBitmap* result, SkIPoint* offset);
/**
* Given the src bounds of an image, this returns the bounds of the result
* image after the filter has been applied.
*/
bool filterBounds(const SkIRect& src, const SkMatrix& ctm, SkIRect* dst);
/**
* Experimental.
*
* If the filter can be expressed as a gaussian-blur, return true and
* set the sigma to the values for horizontal and vertical.
*/
virtual bool asABlur(SkSize* sigma) const;
/**
* Experimental.
*
* If the filter can be expressed as an erode, return true and
* set the radius in X and Y.
*/
virtual bool asAnErode(SkISize* radius) const;
/**
* Experimental.
*
* If the filter can be expressed as a dilation, return true and
* set the radius in X and Y.
*/
virtual bool asADilate(SkISize* radius) const;
protected:
SkImageFilter() {}
explicit SkImageFilter(SkFlattenableReadBuffer& rb) : INHERITED(rb) {}
// Default impl returns false
virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
SkBitmap* result, SkIPoint* offset);
// Default impl copies src into dst and returns true
virtual bool onFilterBounds(const SkIRect&, const SkMatrix&, SkIRect*);
private:
typedef SkFlattenable INHERITED;
};
#endif
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