SkImageFilter.h revision 15356a68b2a87e3ab9fc49392d085a4201ffeb62 
1/*
2 * Copyright 2011 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkImageFilter_DEFINED
9#define SkImageFilter_DEFINED
10
11#include "SkFlattenable.h"
12
13class SkBitmap;
14class SkMatrix;
15struct SkPoint;
16
17/**
18 *  Experimental.
19 *
20 *  Base class for image filters. If one is installed in the paint, then
21 *  all drawing occurs as usual, but it is as if the drawing happened into an
22 *  offscreen (before the xfermode is applied). This offscreen bitmap will
23 *  then be handed to the imagefilter, who in turn creates a new bitmap which
24 *  is what will finally be drawn to the device (using the original xfermode).
25 *
26 *  If the imagefilter returns false, nothing is drawn.
27 */
28class SK_API SkImageFilter : public SkRefCnt /*SkFlattenable*/ {
29public:
30
31    /**
32     *  Request a new (result) image to be created from the src image.
33     *  If the src has no pixels (isNull()) then the request just wants to
34     *  receive the config and width/height of the result.
35     *
36     *  The matrix is the current matrix on the canvas.
37     *
38     *  Offset is the amount to translate the resulting image relative to the
39     *  src when it is drawn.
40     *
41     *  If the result image cannot be created, return false, in which case both
42     *  the result and offset parameters will be ignored by the caller.
43     */
44    bool filterImage(const SkBitmap& src, const SkMatrix&,
45                     SkBitmap* result, SkIPoint* offset);
46
47    /**
48     *  Experimental.
49     *
50     *  If the filter can be expressed as a gaussian-blur, return true and
51     *  set the sigma to the values for horizontal and vertical.
52     */
53    virtual bool asABlur(SkSize* sigma) const;
54
55protected:
56    virtual bool onFilterImage(const SkBitmap& src, const SkMatrix&,
57                               SkBitmap* result, SkIPoint* offset);
58
59private:
60    typedef SkRefCnt INHERITED;
61};
62
63#endif
64