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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 SkIPoint;
struct SkIRect;
struct SkRect;
class GrCustomStage;
class GrTexture;
/**
* 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:
SK_DECLARE_INST_COUNT(SkImageFilter)
class Proxy {
public:
virtual ~Proxy() {};
virtual SkDevice* createDevice(int width, int height) = 0;
// returns true if the proxy can handle this filter natively
virtual bool canHandleImageFilter(SkImageFilter*) = 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;
};
/**
* 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);
/**
* Returns true if the filter can be expressed a single-pass
* GrCustomStage, used to process this filter on the GPU, or false if
* not.
*
* If stage is non-NULL, a new GrCustomStage instance is stored
* in it. The caller assumes ownership of the stage, and it is up to the
* caller to unref it.
*/
virtual bool asNewCustomStage(GrCustomStage** stage, GrTexture*) const;
/**
* Returns true if the filter can be processed on the GPU. This is most
* often used for multi-pass effects, where intermediate results must be
* rendered to textures. For single-pass effects, use asNewCustomStage().
* The default implementation returns false.
*/
virtual bool canFilterImageGPU() const;
/**
* Process this image filter on the GPU. texture is the source texture
* for processing, and rect is the effect region to process. The
* function must allocate a new texture of at least rect width/height
* size, and return it to the caller. The default implementation returns
* NULL.
*/
virtual GrTexture* onFilterImageGPU(GrTexture* texture, const SkRect& rect);
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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