1/* Copyright (C) 2010 The Android Open Source Project 2 * 3 * Licensed under the Apache License, Version 2.0 (the "License"); 4 * you may not use this file except in compliance with the License. 5 * You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software 10 * distributed under the License is distributed on an "AS IS" BASIS, 11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 * See the License for the specific language governing permissions and 13 * limitations under the License. 14 */ 15 16package android.graphics; 17 18import android.content.res.AssetManager; 19 20import java.io.BufferedInputStream; 21import java.io.FileDescriptor; 22import java.io.FileInputStream; 23import java.io.IOException; 24import java.io.InputStream; 25 26/** 27 * BitmapRegionDecoder can be used to decode a rectangle region from an image. 28 * BitmapRegionDecoder is particularly useful when an original image is large and 29 * you only need parts of the image. 30 * 31 * <p>To create a BitmapRegionDecoder, call newInstance(...). 32 * Given a BitmapRegionDecoder, users can call decodeRegion() repeatedly 33 * to get a decoded Bitmap of the specified region. 34 * 35 */ 36public final class BitmapRegionDecoder { 37 private int mNativeBitmapRegionDecoder; 38 private boolean mRecycled; 39 // ensures that the native decoder object exists and that only one decode can 40 // occur at a time. 41 private final Object mNativeLock = new Object(); 42 43 /** 44 * Create a BitmapRegionDecoder from the specified byte array. 45 * Currently only the JPEG and PNG formats are supported. 46 * 47 * @param data byte array of compressed image data. 48 * @param offset offset into data for where the decoder should begin 49 * parsing. 50 * @param length the number of bytes, beginning at offset, to parse 51 * @param isShareable If this is true, then the BitmapRegionDecoder may keep a 52 * shallow reference to the input. If this is false, 53 * then the BitmapRegionDecoder will explicitly make a copy of the 54 * input data, and keep that. Even if sharing is allowed, 55 * the implementation may still decide to make a deep 56 * copy of the input data. If an image is progressively encoded, 57 * allowing sharing may degrade the decoding speed. 58 * @return BitmapRegionDecoder, or null if the image data could not be decoded. 59 * @throws IOException if the image format is not supported or can not be decoded. 60 */ 61 public static BitmapRegionDecoder newInstance(byte[] data, 62 int offset, int length, boolean isShareable) throws IOException { 63 if ((offset | length) < 0 || data.length < offset + length) { 64 throw new ArrayIndexOutOfBoundsException(); 65 } 66 return nativeNewInstance(data, offset, length, isShareable); 67 } 68 69 /** 70 * Create a BitmapRegionDecoder from the file descriptor. 71 * The position within the descriptor will not be changed when 72 * this returns, so the descriptor can be used again as is. 73 * Currently only the JPEG and PNG formats are supported. 74 * 75 * @param fd The file descriptor containing the data to decode 76 * @param isShareable If this is true, then the BitmapRegionDecoder may keep a 77 * shallow reference to the input. If this is false, 78 * then the BitmapRegionDecoder will explicitly make a copy of the 79 * input data, and keep that. Even if sharing is allowed, 80 * the implementation may still decide to make a deep 81 * copy of the input data. If an image is progressively encoded, 82 * allowing sharing may degrade the decoding speed. 83 * @return BitmapRegionDecoder, or null if the image data could not be decoded. 84 * @throws IOException if the image format is not supported or can not be decoded. 85 */ 86 public static BitmapRegionDecoder newInstance( 87 FileDescriptor fd, boolean isShareable) throws IOException { 88 return nativeNewInstance(fd, isShareable); 89 } 90 91 /** 92 * Create a BitmapRegionDecoder from an input stream. 93 * The stream's position will be where ever it was after the encoded data 94 * was read. 95 * Currently only the JPEG and PNG formats are supported. 96 * 97 * @param is The input stream that holds the raw data to be decoded into a 98 * BitmapRegionDecoder. 99 * @param isShareable If this is true, then the BitmapRegionDecoder may keep a 100 * shallow reference to the input. If this is false, 101 * then the BitmapRegionDecoder will explicitly make a copy of the 102 * input data, and keep that. Even if sharing is allowed, 103 * the implementation may still decide to make a deep 104 * copy of the input data. If an image is progressively encoded, 105 * allowing sharing may degrade the decoding speed. 106 * @return BitmapRegionDecoder, or null if the image data could not be decoded. 107 * @throws IOException if the image format is not supported or can not be decoded. 108 */ 109 public static BitmapRegionDecoder newInstance(InputStream is, 110 boolean isShareable) throws IOException { 111 // we need mark/reset to work properly in JNI 112 113 if (!is.markSupported()) { 114 is = new BufferedInputStream(is, 16 * 1024); 115 } 116 117 if (is instanceof AssetManager.AssetInputStream) { 118 return nativeNewInstance( 119 ((AssetManager.AssetInputStream) is).getAssetInt(), 120 isShareable); 121 } else { 122 // pass some temp storage down to the native code. 1024 is made up, 123 // but should be large enough to avoid too many small calls back 124 // into is.read(...). 125 byte [] tempStorage = new byte[16 * 1024]; 126 return nativeNewInstance(is, tempStorage, isShareable); 127 } 128 } 129 130 /** 131 * Create a BitmapRegionDecoder from a file path. 132 * Currently only the JPEG and PNG formats are supported. 133 * 134 * @param pathName complete path name for the file to be decoded. 135 * @param isShareable If this is true, then the BitmapRegionDecoder may keep a 136 * shallow reference to the input. If this is false, 137 * then the BitmapRegionDecoder will explicitly make a copy of the 138 * input data, and keep that. Even if sharing is allowed, 139 * the implementation may still decide to make a deep 140 * copy of the input data. If an image is progressively encoded, 141 * allowing sharing may degrade the decoding speed. 142 * @return BitmapRegionDecoder, or null if the image data could not be decoded. 143 * @throws IOException if the image format is not supported or can not be decoded. 144 */ 145 public static BitmapRegionDecoder newInstance(String pathName, 146 boolean isShareable) throws IOException { 147 BitmapRegionDecoder decoder = null; 148 InputStream stream = null; 149 150 try { 151 stream = new FileInputStream(pathName); 152 decoder = newInstance(stream, isShareable); 153 } finally { 154 if (stream != null) { 155 try { 156 stream.close(); 157 } catch (IOException e) { 158 // do nothing here 159 } 160 } 161 } 162 return decoder; 163 } 164 165 /* Private constructor that must receive an already allocated native 166 region decoder int (pointer). 167 168 This can be called from JNI code. 169 */ 170 private BitmapRegionDecoder(int decoder) { 171 mNativeBitmapRegionDecoder = decoder; 172 mRecycled = false; 173 } 174 175 /** 176 * Decodes a rectangle region in the image specified by rect. 177 * 178 * @param rect The rectangle that specified the region to be decode. 179 * @param options null-ok; Options that control downsampling. 180 * inPurgeable is not supported. 181 * @return The decoded bitmap, or null if the image data could not be 182 * decoded. 183 */ 184 public Bitmap decodeRegion(Rect rect, BitmapFactory.Options options) { 185 synchronized (mNativeLock) { 186 checkRecycled("decodeRegion called on recycled region decoder"); 187 if (rect.right <= 0 || rect.bottom <= 0 || rect.left >= getWidth() 188 || rect.top >= getHeight()) 189 throw new IllegalArgumentException("rectangle is outside the image"); 190 return nativeDecodeRegion(mNativeBitmapRegionDecoder, rect.left, rect.top, 191 rect.right - rect.left, rect.bottom - rect.top, options); 192 } 193 } 194 195 /** Returns the original image's width */ 196 public int getWidth() { 197 synchronized (mNativeLock) { 198 checkRecycled("getWidth called on recycled region decoder"); 199 return nativeGetWidth(mNativeBitmapRegionDecoder); 200 } 201 } 202 203 /** Returns the original image's height */ 204 public int getHeight() { 205 synchronized (mNativeLock) { 206 checkRecycled("getHeight called on recycled region decoder"); 207 return nativeGetHeight(mNativeBitmapRegionDecoder); 208 } 209 } 210 211 /** 212 * Frees up the memory associated with this region decoder, and mark the 213 * region decoder as "dead", meaning it will throw an exception if decodeRegion(), 214 * getWidth() or getHeight() is called. 215 * 216 * <p>This operation cannot be reversed, so it should only be called if you are 217 * sure there are no further uses for the region decoder. This is an advanced call, 218 * and normally need not be called, since the normal GC process will free up this 219 * memory when there are no more references to this region decoder. 220 */ 221 public void recycle() { 222 synchronized (mNativeLock) { 223 if (!mRecycled) { 224 nativeClean(mNativeBitmapRegionDecoder); 225 mRecycled = true; 226 } 227 } 228 } 229 230 /** 231 * Returns true if this region decoder has been recycled. 232 * If so, then it is an error to try use its method. 233 * 234 * @return true if the region decoder has been recycled 235 */ 236 public final boolean isRecycled() { 237 return mRecycled; 238 } 239 240 /** 241 * Called by methods that want to throw an exception if the region decoder 242 * has already been recycled. 243 */ 244 private void checkRecycled(String errorMessage) { 245 if (mRecycled) { 246 throw new IllegalStateException(errorMessage); 247 } 248 } 249 250 @Override 251 protected void finalize() throws Throwable { 252 try { 253 recycle(); 254 } finally { 255 super.finalize(); 256 } 257 } 258 259 private static native Bitmap nativeDecodeRegion(int lbm, 260 int start_x, int start_y, int width, int height, 261 BitmapFactory.Options options); 262 private static native int nativeGetWidth(int lbm); 263 private static native int nativeGetHeight(int lbm); 264 private static native void nativeClean(int lbm); 265 266 private static native BitmapRegionDecoder nativeNewInstance( 267 byte[] data, int offset, int length, boolean isShareable); 268 private static native BitmapRegionDecoder nativeNewInstance( 269 FileDescriptor fd, boolean isShareable); 270 private static native BitmapRegionDecoder nativeNewInstance( 271 InputStream is, byte[] storage, boolean isShareable); 272 private static native BitmapRegionDecoder nativeNewInstance( 273 int asset, boolean isShareable); 274} 275