1/*
2 * Copyright (c) 2008, Google Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 *     * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *     * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 *     * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#ifndef NativeImageSkia_h
32#define NativeImageSkia_h
33
34#include "SkBitmap.h"
35#include "IntSize.h"
36
37namespace WebCore {
38
39// This object is used as the "native image" in our port. When WebKit uses
40// "NativeImagePtr", it is a pointer to this type. It is an SkBitmap, but also
41// stores a cached resized image.
42class NativeImageSkia : public SkBitmap {
43public:
44    NativeImageSkia();
45    ~NativeImageSkia();
46
47    // This constructor does a shallow copy of the passed-in SkBitmap (ie., it
48    // references the same pixel data and bumps the refcount).  Use only when
49    // you want sharing semantics.
50    explicit NativeImageSkia(const SkBitmap&);
51
52    // Returns the number of bytes of image data. This includes the cached
53    // resized version if there is one.
54    int decodedSize() const;
55
56    // Sets the data complete flag. This is called by the image decoder when
57    // all data is complete, and used by us to know whether we can cache
58    // resized images.
59    void setDataComplete() { m_isDataComplete = true; }
60
61    // Returns true if the entire image has been decoded.
62    bool isDataComplete() const { return m_isDataComplete; }
63
64    // We can keep a resized version of the bitmap cached on this object.
65    // This function will return true if there is a cached version of the
66    // given image subset with the given dimensions.
67    bool hasResizedBitmap(int width, int height) const;
68
69    // This will return an existing resized image, or generate a new one of
70    // the specified size and store it in the cache. Subsetted images can not
71    // be cached unless the subset is the entire bitmap.
72    SkBitmap resizedBitmap(int width, int height) const;
73
74    // Returns true if the given resize operation should either resize the whole
75    // image and cache it, or resize just the part it needs and throw the result
76    // away.
77    //
78    // On the one hand, if only a small subset is desired, then we will waste a
79    // lot of time resampling the entire thing, so we only want to do exactly
80    // what's required. On the other hand, resampling the entire bitmap is
81    // better if we're going to be using it more than once (like a bitmap
82    // scrolling on and off the screen. Since we only cache when doing the
83    // entire thing, it's best to just do it up front.
84    bool shouldCacheResampling(int destWidth,
85                               int destHeight,
86                               int destSubsetWidth,
87                               int destSubsetHeight) const;
88
89private:
90    // Set to true when the data is complete. Before the entire image has
91    // loaded, we do not want to cache a resize.
92    bool m_isDataComplete;
93
94    // The cached bitmap. This will be empty() if there is no cached image.
95    mutable SkBitmap m_resizedImage;
96
97    // References how many times that the image size has been requested for
98    // the last size.
99    //
100    // Every time we get a request, if it matches the m_lastRequestSize, we'll
101    // increment the counter, and if not, we'll reset the counter and save the
102    // size.
103    //
104    // This allows us to see if many requests have been made for the same
105    // resized image, we know that we should probably cache it, even if all of
106    // those requests individually are small and would not otherwise be cached.
107    mutable IntSize m_lastRequestSize;
108    mutable int m_resizeRequests;
109};
110
111}
112#endif  // NativeImageSkia_h
113
114