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BitmapRegionDecoder

public final class BitmapRegionDecoder
extends Object

java.lang.Object
   ↳ android.graphics.BitmapRegionDecoder


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.

To create a BitmapRegionDecoder, call newInstance(...). Given a BitmapRegionDecoder, users can call decodeRegion() repeatedly to get a decoded Bitmap of the specified region.

Summary

Public methods

Bitmap decodeRegion(Rect rect, BitmapFactory.Options options)

Decodes a rectangle region in the image specified by rect.

int getHeight()

Returns the original image's height

int getWidth()

Returns the original image's width

final boolean isRecycled()

Returns true if this region decoder has been recycled.

static BitmapRegionDecoder newInstance(InputStream is, boolean isShareable)

Create a BitmapRegionDecoder from an input stream.

static BitmapRegionDecoder newInstance(FileDescriptor fd, boolean isShareable)

Create a BitmapRegionDecoder from the file descriptor.

static BitmapRegionDecoder newInstance(String pathName, boolean isShareable)

Create a BitmapRegionDecoder from a file path.

static BitmapRegionDecoder newInstance(byte[] data, int offset, int length, boolean isShareable)

Create a BitmapRegionDecoder from the specified byte array.

void recycle()

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.

Protected methods

void finalize()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

Inherited methods

From class java.lang.Object

Public methods

decodeRegion

Added in API level 10
Bitmap decodeRegion (Rect rect, 
                BitmapFactory.Options options)

Decodes a rectangle region in the image specified by rect.

Parameters
rect Rect: The rectangle that specified the region to be decode.
options BitmapFactory.Options: null-ok; Options that control downsampling. inPurgeable is not supported.
Returns
Bitmap The decoded bitmap, or null if the image data could not be decoded.

getHeight

Added in API level 10
int getHeight ()

Returns the original image's height

Returns
int

getWidth

Added in API level 10
int getWidth ()

Returns the original image's width

Returns
int

isRecycled

Added in API level 10
boolean isRecycled ()

Returns true if this region decoder has been recycled. If so, then it is an error to try use its method.

Returns
boolean true if the region decoder has been recycled

newInstance

Added in API level 10
BitmapRegionDecoder newInstance (InputStream is, 
                boolean 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.

Parameters
is InputStream: The input stream that holds the raw data to be decoded into a BitmapRegionDecoder.
isShareable boolean: 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.
Returns
BitmapRegionDecoder 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.

Prior to KITKAT, if is.markSupported() returns true, is.mark(1024) would be called. As of KITKAT, this is no longer the case.

newInstance

Added in API level 10
BitmapRegionDecoder newInstance (FileDescriptor fd, 
                boolean 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.

Parameters
fd FileDescriptor: The file descriptor containing the data to decode
isShareable boolean: 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.
Returns
BitmapRegionDecoder 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.

newInstance

Added in API level 10
BitmapRegionDecoder newInstance (String pathName, 
                boolean isShareable)

Create a BitmapRegionDecoder from a file path. Currently only the JPEG and PNG formats are supported.

Parameters
pathName String: complete path name for the file to be decoded.
isShareable boolean: 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.
Returns
BitmapRegionDecoder 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.

newInstance

Added in API level 10
BitmapRegionDecoder newInstance (byte[] data, 
                int offset, 
                int length, 
                boolean isShareable)

Create a BitmapRegionDecoder from the specified byte array. Currently only the JPEG and PNG formats are supported.

Parameters
data byte: byte array of compressed image data.
offset int: offset into data for where the decoder should begin parsing.
length int: the number of bytes, beginning at offset, to parse
isShareable boolean: 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.
Returns
BitmapRegionDecoder 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.

recycle

Added in API level 10
void recycle ()

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.

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.

Protected methods

finalize

Added in API level 10
void finalize ()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. A subclass overrides the finalize method to dispose of system resources or to perform other cleanup.

The general contract of finalize is that it is invoked if and when the JavaTM virtual machine has determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, except as a result of an action taken by the finalization of some other object or class which is ready to be finalized. The finalize method may take any action, including making this object available again to other threads; the usual purpose of finalize, however, is to perform cleanup actions before the object is irrevocably discarded. For example, the finalize method for an object that represents an input/output connection might perform explicit I/O transactions to break the connection before the object is permanently discarded.

The finalize method of class Object performs no special action; it simply returns normally. Subclasses of Object may override this definition.

The Java programming language does not guarantee which thread will invoke the finalize method for any given object. It is guaranteed, however, that the thread that invokes finalize will not be holding any user-visible synchronization locks when finalize is invoked. If an uncaught exception is thrown by the finalize method, the exception is ignored and finalization of that object terminates.

After the finalize method has been invoked for an object, no further action is taken until the Java virtual machine has again determined that there is no longer any means by which this object can be accessed by any thread that has not yet died, including possible actions by other objects or classes which are ready to be finalized, at which point the object may be discarded.

The finalize method is never invoked more than once by a Java virtual machine for any given object.

Any exception thrown by the finalize method causes the finalization of this object to be halted, but is otherwise ignored.

Throws
Throwable
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