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      1 /*
      2  * Copyright (C) 2006 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 
     17 package android.graphics;
     18 
     19 /**
     20  * LargeBitmap can be used to decode a rectangle region from an image.
     21  * LargeBimap is particularly useful when an original image is large and
     22  * you only need parts of the image.
     23  *
     24  * To create a LargeBitmap, call BitmapFactory.createLargeBitmap().
     25  * Given a LargeBitmap, users can call decodeRegion() repeatedly
     26  * to get a decoded Bitmap of the specified region.
     27  * @hide
     28  */
     29 public final class LargeBitmap {
     30     private long mNativeLargeBitmap;
     31     private boolean mRecycled;
     32 
     33     /*  Private constructor that must received an already allocated native
     34         large bitmap int (pointer).
     35 
     36         This can be called from JNI code.
     37     */
     38     private LargeBitmap(long nativeLbm) {
     39         mNativeLargeBitmap = nativeLbm;
     40         mRecycled = false;
     41     }
     42 
     43     /**
     44      * Decodes a rectangle region in the image specified by rect.
     45      *
     46      * @param rect The rectangle that specified the region to be decode.
     47      * @param opts null-ok; Options that control downsampling.
     48      *             inPurgeable is not supported.
     49      * @return The decoded bitmap, or null if the image data could not be
     50      *         decoded.
     51      */
     52     public Bitmap decodeRegion(Rect rect, BitmapFactory.Options options) {
     53         checkRecycled("decodeRegion called on recycled large bitmap");
     54         if (rect.left < 0 || rect.top < 0 || rect.right > getWidth() || rect.bottom > getHeight())
     55             throw new IllegalArgumentException("rectangle is not inside the image");
     56         return nativeDecodeRegion(mNativeLargeBitmap, rect.left, rect.top,
     57                 rect.right - rect.left, rect.bottom - rect.top, options);
     58     }
     59 
     60     /** Returns the original image's width */
     61     public int getWidth() {
     62         checkRecycled("getWidth called on recycled large bitmap");
     63         return nativeGetWidth(mNativeLargeBitmap);
     64     }
     65 
     66     /** Returns the original image's height */
     67     public int getHeight() {
     68         checkRecycled("getHeight called on recycled large bitmap");
     69         return nativeGetHeight(mNativeLargeBitmap);
     70     }
     71 
     72     /**
     73      * Frees up the memory associated with this large bitmap, and mark the
     74      * large bitmap as "dead", meaning it will throw an exception if decodeRegion(),
     75      * getWidth() or getHeight() is called.
     76      * This operation cannot be reversed, so it should only be called if you are
     77      * sure there are no further uses for the large bitmap. This is an advanced call,
     78      * and normally need not be called, since the normal GC process will free up this
     79      * memory when there are no more references to this bitmap.
     80      */
     81     public void recycle() {
     82         if (!mRecycled) {
     83             nativeClean(mNativeLargeBitmap);
     84             mRecycled = true;
     85         }
     86     }
     87 
     88     /**
     89      * Returns true if this large bitmap has been recycled.
     90      * If so, then it is an error to try use its method.
     91      *
     92      * @return true if the large bitmap has been recycled
     93      */
     94     public final boolean isRecycled() {
     95         return mRecycled;
     96     }
     97 
     98     /**
     99      * Called by methods that want to throw an exception if the bitmap
    100      * has already been recycled.
    101      */
    102     private void checkRecycled(String errorMessage) {
    103         if (mRecycled) {
    104             throw new IllegalStateException(errorMessage);
    105         }
    106     }
    107 
    108     protected void finalize() {
    109         recycle();
    110     }
    111 
    112     private static native Bitmap nativeDecodeRegion(long nativeLbm,
    113             int start_x, int start_y, int width, int height,
    114             BitmapFactory.Options options);
    115     private static native int nativeGetWidth(long nativeLbm);
    116     private static native int nativeGetHeight(long nativeLbm);
    117     private static native void nativeClean(long nativeLbm);
    118 }
    119