/* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.graphics;
import android.content.res.AssetManager;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* BitmapRegionDecoder can be used to decode a rectangle region from an image.
* BitmapRegionDecoder is particularly useful when an original image is large and
* you only need parts of the image.
*
* <p>To create a BitmapRegionDecoder, call newInstance(...).
* Given a BitmapRegionDecoder, users can call decodeRegion() repeatedly
* to get a decoded Bitmap of the specified region.
*
*/
public final class BitmapRegionDecoder {
private long mNativeBitmapRegionDecoder;
private boolean mRecycled;
// ensures that the native decoder object exists and that only one decode can
// occur at a time.
private final Object mNativeLock = new Object();
/**
* Create a BitmapRegionDecoder from the specified byte array.
* Currently only the JPEG and PNG formats are supported.
*
* @param data byte array of compressed image data.
* @param offset offset into data for where the decoder should begin
* parsing.
* @param length the number of bytes, beginning at offset, to parse
* @param isShareable If this is true, then the BitmapRegionDecoder may keep a
* shallow reference to the input. If this is false,
* then the BitmapRegionDecoder will explicitly make a copy of the
* input data, and keep that. Even if sharing is allowed,
* the implementation may still decide to make a deep
* copy of the input data. If an image is progressively encoded,
* allowing sharing may degrade the decoding speed.
* @return BitmapRegionDecoder, or null if the image data could not be decoded.
* @throws IOException if the image format is not supported or can not be decoded.
*/
public static BitmapRegionDecoder newInstance(byte[] data,
int offset, int length, boolean isShareable) throws IOException {
if ((offset | length) < 0 || data.length < offset + length) {
throw new ArrayIndexOutOfBoundsException();
}
return nativeNewInstance(data, offset, length, isShareable);
}
/**
* Create a BitmapRegionDecoder from the file descriptor.
* The position within the descriptor will not be changed when
* this returns, so the descriptor can be used again as is.
* Currently only the JPEG and PNG formats are supported.
*
* @param fd The file descriptor containing the data to decode
* @param isShareable If this is true, then the BitmapRegionDecoder may keep a
* shallow reference to the input. If this is false,
* then the BitmapRegionDecoder will explicitly make a copy of the
* input data, and keep that. Even if sharing is allowed,
* the implementation may still decide to make a deep
* copy of the input data. If an image is progressively encoded,
* allowing sharing may degrade the decoding speed.
* @return BitmapRegionDecoder, or null if the image data could not be decoded.
* @throws IOException if the image format is not supported or can not be decoded.
*/
public static BitmapRegionDecoder newInstance(
FileDescriptor fd, boolean isShareable) throws IOException {
return nativeNewInstance(fd, isShareable);
}
/**
* Create a BitmapRegionDecoder from an input stream.
* The stream's position will be where ever it was after the encoded data
* was read.
* Currently only the JPEG and PNG formats are supported.
*
* @param is The input stream that holds the raw data to be decoded into a
* BitmapRegionDecoder.
* @param isShareable If this is true, then the BitmapRegionDecoder may keep a
* shallow reference to the input. If this is false,
* then the BitmapRegionDecoder will explicitly make a copy of the
* input data, and keep that. Even if sharing is allowed,
* the implementation may still decide to make a deep
* copy of the input data. If an image is progressively encoded,
* allowing sharing may degrade the decoding speed.
* @return BitmapRegionDecoder, or null if the image data could not be decoded.
* @throws IOException if the image format is not supported or can not be decoded.
*
* <p class="note">Prior to {@link android.os.Build.VERSION_CODES#KITKAT},
* if {@link InputStream#markSupported is.markSupported()} returns true,
* <code>is.mark(1024)</code> would be called. As of
* {@link android.os.Build.VERSION_CODES#KITKAT}, this is no longer the case.</p>
*/
public static BitmapRegionDecoder newInstance(InputStream is,
boolean isShareable) throws IOException {
if (is instanceof AssetManager.AssetInputStream) {
return nativeNewInstance(
((AssetManager.AssetInputStream) is).getNativeAsset(),
isShareable);
} else {
// pass some temp storage down to the native code. 1024 is made up,
// but should be large enough to avoid too many small calls back
// into is.read(...).
byte [] tempStorage = new byte[16 * 1024];
return nativeNewInstance(is, tempStorage, isShareable);
}
}
/**
* Create a BitmapRegionDecoder from a file path.
* Currently only the JPEG and PNG formats are supported.
*
* @param pathName complete path name for the file to be decoded.
* @param isShareable If this is true, then the BitmapRegionDecoder may keep a
* shallow reference to the input. If this is false,
* then the BitmapRegionDecoder will explicitly make a copy of the
* input data, and keep that. Even if sharing is allowed,
* the implementation may still decide to make a deep
* copy of the input data. If an image is progressively encoded,
* allowing sharing may degrade the decoding speed.
* @return BitmapRegionDecoder, or null if the image data could not be decoded.
* @throws IOException if the image format is not supported or can not be decoded.
*/
public static BitmapRegionDecoder newInstance(String pathName,
boolean isShareable) throws IOException {
BitmapRegionDecoder decoder = null;
InputStream stream = null;
try {
stream = new FileInputStream(pathName);
decoder = newInstance(stream, isShareable);
} finally {
if (stream != null) {
try {
stream.close();
} catch (IOException e) {
// do nothing here
}
}
}
return decoder;
}
/* Private constructor that must receive an already allocated native
region decoder int (pointer).
This can be called from JNI code.
*/
private BitmapRegionDecoder(long decoder) {
mNativeBitmapRegionDecoder = decoder;
mRecycled = false;
}
/**
* Decodes a rectangle region in the image specified by rect.
*
* @param rect The rectangle that specified the region to be decode.
* @param options null-ok; Options that control downsampling.
* inPurgeable is not supported.
* @return The decoded bitmap, or null if the image data could not be
* decoded.
*/
public Bitmap decodeRegion(Rect rect, BitmapFactory.Options options) {
synchronized (mNativeLock) {
checkRecycled("decodeRegion called on recycled region decoder");
if (rect.right <= 0 || rect.bottom <= 0 || rect.left >= getWidth()
|| rect.top >= getHeight())
throw new IllegalArgumentException("rectangle is outside the image");
return nativeDecodeRegion(mNativeBitmapRegionDecoder, rect.left, rect.top,
rect.right - rect.left, rect.bottom - rect.top, options);
}
}
/** Returns the original image's width */
public int getWidth() {
synchronized (mNativeLock) {
checkRecycled("getWidth called on recycled region decoder");
return nativeGetWidth(mNativeBitmapRegionDecoder);
}
}
/** Returns the original image's height */
public int getHeight() {
synchronized (mNativeLock) {
checkRecycled("getHeight called on recycled region decoder");
return nativeGetHeight(mNativeBitmapRegionDecoder);
}
}
/**
* Frees up the memory associated with this region decoder, and mark the
* region decoder as "dead", meaning it will throw an exception if decodeRegion(),
* getWidth() or getHeight() is called.
*
* <p>This operation cannot be reversed, so it should only be called if you are
* sure there are no further uses for the region decoder. This is an advanced call,
* and normally need not be called, since the normal GC process will free up this
* memory when there are no more references to this region decoder.
*/
public void recycle() {
synchronized (mNativeLock) {
if (!mRecycled) {
nativeClean(mNativeBitmapRegionDecoder);
mRecycled = true;
}
}
}
/**
* Returns true if this region decoder has been recycled.
* If so, then it is an error to try use its method.
*
* @return true if the region decoder has been recycled
*/
public final boolean isRecycled() {
return mRecycled;
}
/**
* Called by methods that want to throw an exception if the region decoder
* has already been recycled.
*/
private void checkRecycled(String errorMessage) {
if (mRecycled) {
throw new IllegalStateException(errorMessage);
}
}
@Override
protected void finalize() throws Throwable {
try {
recycle();
} finally {
super.finalize();
}
}
private static native Bitmap nativeDecodeRegion(long lbm,
int start_x, int start_y, int width, int height,
BitmapFactory.Options options);
private static native int nativeGetWidth(long lbm);
private static native int nativeGetHeight(long lbm);
private static native void nativeClean(long lbm);
private static native BitmapRegionDecoder nativeNewInstance(
byte[] data, int offset, int length, boolean isShareable);
private static native BitmapRegionDecoder nativeNewInstance(
FileDescriptor fd, boolean isShareable);
private static native BitmapRegionDecoder nativeNewInstance(
InputStream is, byte[] storage, boolean isShareable);
private static native BitmapRegionDecoder nativeNewInstance(
long asset, boolean isShareable);
}
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