1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.graphics;
18
19import java.io.InputStream;
20import java.io.OutputStream;
21
22/**
23 * A Picture records drawing calls (via the canvas returned by beginRecording)
24 * and can then play them back into Canvas (via {@link Picture#draw(Canvas)} or
25 * {@link Canvas#drawPicture(Picture)}).For most content (e.g. text, lines, rectangles),
26 * drawing a sequence from a picture can be faster than the equivalent API
27 * calls, since the picture performs its playback without incurring any
28 * method-call overhead.
29 *
30 * <p class="note"><strong>Note:</strong> Prior to API level 23 a picture cannot
31 * be replayed on a hardware accelerated canvas.</p>
32 */
33public class Picture {
34    private Canvas mRecordingCanvas;
35    private long mNativePicture;
36
37    private static final int WORKING_STREAM_STORAGE = 16 * 1024;
38
39    /**
40     * Creates an empty picture that is ready to record.
41     */
42    public Picture() {
43        this(nativeConstructor(0));
44    }
45
46    /**
47     * Create a picture by making a copy of what has already been recorded in
48     * src. The contents of src are unchanged, and if src changes later, those
49     * changes will not be reflected in this picture.
50     */
51    public Picture(Picture src) {
52        this(nativeConstructor(src != null ? src.mNativePicture : 0));
53    }
54
55    private Picture(long nativePicture) {
56        if (nativePicture == 0) {
57            throw new RuntimeException();
58        }
59        mNativePicture = nativePicture;
60    }
61
62    @Override
63    protected void finalize() throws Throwable {
64        try {
65            nativeDestructor(mNativePicture);
66            mNativePicture = 0;
67        } finally {
68            super.finalize();
69        }
70    }
71
72    /**
73     * To record a picture, call beginRecording() and then draw into the Canvas
74     * that is returned. Nothing we appear on screen, but all of the draw
75     * commands (e.g. {@link Canvas#drawRect(Rect, Paint)}) will be recorded.
76     * To stop recording, call endRecording(). After endRecording() the Canvas
77     * that was returned must no longer be used, and nothing should be drawn
78     * into it.
79     */
80    public Canvas beginRecording(int width, int height) {
81        long ni = nativeBeginRecording(mNativePicture, width, height);
82        mRecordingCanvas = new RecordingCanvas(this, ni);
83        return mRecordingCanvas;
84    }
85
86    /**
87     * Call endRecording when the picture is built. After this call, the picture
88     * may be drawn, but the canvas that was returned by beginRecording must not
89     * be used anymore. This is automatically called if {@link Picture#draw}
90     * or {@link Canvas#drawPicture(Picture)} is called.
91     */
92    public void endRecording() {
93        if (mRecordingCanvas != null) {
94            mRecordingCanvas = null;
95            nativeEndRecording(mNativePicture);
96        }
97    }
98
99    /**
100     * Get the width of the picture as passed to beginRecording. This
101     * does not reflect (per se) the content of the picture.
102     */
103    public int getWidth() {
104      return nativeGetWidth(mNativePicture);
105    }
106
107    /**
108     * Get the height of the picture as passed to beginRecording. This
109     * does not reflect (per se) the content of the picture.
110     */
111    public int getHeight() {
112      return nativeGetHeight(mNativePicture);
113    }
114
115    /**
116     * Draw this picture on the canvas.
117     * <p>
118     * Prior to {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this call could
119     * have the side effect of changing the matrix and clip of the canvas
120     * if this picture had imbalanced saves/restores.
121     *
122     * <p>
123     * <strong>Note:</strong> This forces the picture to internally call
124     * {@link Picture#endRecording()} in order to prepare for playback.
125     *
126     * @param canvas  The picture is drawn to this canvas
127     */
128    public void draw(Canvas canvas) {
129        if (mRecordingCanvas != null) {
130            endRecording();
131        }
132        nativeDraw(canvas.getNativeCanvasWrapper(), mNativePicture);
133    }
134
135    /**
136     * Create a new picture (already recorded) from the data in the stream. This
137     * data was generated by a previous call to writeToStream(). Pictures that
138     * have been persisted across device restarts are not guaranteed to decode
139     * properly and are highly discouraged.
140     *
141     * @see #writeToStream(java.io.OutputStream)
142     * @deprecated The recommended alternative is to not use writeToStream and
143     * instead draw the picture into a Bitmap from which you can persist it as
144     * raw or compressed pixels.
145     */
146    @Deprecated
147    public static Picture createFromStream(InputStream stream) {
148        return new Picture(nativeCreateFromStream(stream, new byte[WORKING_STREAM_STORAGE]));
149    }
150
151    /**
152     * Write the picture contents to a stream. The data can be used to recreate
153     * the picture in this or another process by calling createFromStream(...)
154     * The resulting stream is NOT to be persisted across device restarts as
155     * there is no guarantee that the Picture can be successfully reconstructed.
156     *
157     * @see #createFromStream(java.io.InputStream)
158     * @deprecated The recommended alternative is to draw the picture into a
159     * Bitmap from which you can persist it as raw or compressed pixels.
160     */
161    @Deprecated
162    public void writeToStream(OutputStream stream) {
163        // do explicit check before calling the native method
164        if (stream == null) {
165            throw new NullPointerException();
166        }
167        if (!nativeWriteToStream(mNativePicture, stream,
168                             new byte[WORKING_STREAM_STORAGE])) {
169            throw new RuntimeException();
170        }
171    }
172
173    // return empty picture if src is 0, or a copy of the native src
174    private static native long nativeConstructor(long nativeSrcOr0);
175    private static native long nativeCreateFromStream(InputStream stream, byte[] storage);
176    private static native int nativeGetWidth(long nativePicture);
177    private static native int nativeGetHeight(long nativePicture);
178    private static native long nativeBeginRecording(long nativeCanvas, int w, int h);
179    private static native void nativeEndRecording(long nativeCanvas);
180    private static native void nativeDraw(long nativeCanvas, long nativePicture);
181    private static native boolean nativeWriteToStream(long nativePicture,
182                                           OutputStream stream, byte[] storage);
183    private static native void nativeDestructor(long nativePicture);
184
185    private static class RecordingCanvas extends Canvas {
186        private final Picture mPicture;
187
188        public RecordingCanvas(Picture pict, long nativeCanvas) {
189            super(nativeCanvas);
190            mPicture = pict;
191        }
192
193        @Override
194        public void setBitmap(Bitmap bitmap) {
195            throw new RuntimeException("Cannot call setBitmap on a picture canvas");
196        }
197
198        @Override
199        public void drawPicture(Picture picture) {
200            if (mPicture == picture) {
201                throw new RuntimeException("Cannot draw a picture into its recording canvas");
202            }
203            super.drawPicture(picture);
204        }
205    }
206}
207