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