SkCachingPixelRef.h revision 27f890219b09e4774da75e6a11ec82849eadae5a 
1/*
2 * Copyright 2013 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 SkCachingPixelRef_DEFINED
9#define SkCachingPixelRef_DEFINED
10
11#include "SkImageInfo.h"
12#include "SkImageGenerator.h"
13#include "SkPixelRef.h"
14
15class SkColorTable;
16
17/**
18 *  PixelRef which defers decoding until SkBitmap::lockPixels() is
19 *  called.  Caches the decoded images in the global
20 *  SkScaledImageCache.  When the pixels are unlocked, this cache may
21 *  or be destroyed before the next lock.  If so, onLockPixels will
22 *  attempt to re-decode.
23 *
24 *  Decoding is handled by the SkImageGenerator
25 */
26class SkCachingPixelRef : public SkPixelRef {
27public:
28    /**
29     *  Takes ownership of SkImageGenerator.  If this method fails for
30     *  whatever reason, it will return false and immediatetely delete
31     *  the generator.  If it succeeds, it will modify destination
32     *  bitmap.
33     *
34     *  If Install fails or when the SkCachingPixelRef that is
35     *  installed into destination is destroyed, it will call
36     *  SkDELETE() on the generator.  Therefore, generator should be
37     *  allocated with SkNEW() or SkNEW_ARGS().
38     */
39    static bool Install(SkImageGenerator* gen, SkBitmap* dst);
40
41protected:
42    virtual ~SkCachingPixelRef();
43    virtual void* onLockPixels(SkColorTable** colorTable) SK_OVERRIDE;
44    virtual void onUnlockPixels() SK_OVERRIDE;
45    virtual bool onLockPixelsAreWritable() const SK_OVERRIDE { return false; }
46
47    virtual SkData* onRefEncodedData() SK_OVERRIDE {
48        return fImageGenerator->refEncodedData();
49    }
50    // No need to flatten this object. When flattening an SkBitmap,
51    // SkOrderedWriteBuffer will check the encoded data and write that
52    // instead.
53    // Future implementations of SkFlattenableWriteBuffer will need to
54    // special case for onRefEncodedData as well.
55    SK_DECLARE_UNFLATTENABLE_OBJECT()
56
57private:
58    SkImageGenerator* const fImageGenerator;
59    bool                    fErrorInDecoding;
60    void*                   fScaledCacheId;
61    const size_t            fRowBytes;
62
63    SkCachingPixelRef(const SkImageInfo&, SkImageGenerator*, size_t rowBytes);
64
65    typedef SkPixelRef INHERITED;
66};
67
68#endif  // SkCachingPixelRef_DEFINED
69