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.
Public methods | |
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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 | |
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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 | |
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From
class
java.lang.Object
|
Bitmap decodeRegion (Rect rect, BitmapFactory.Options options)
Decodes a rectangle region in the image specified by rect.
Parameters | |
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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. |
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 |
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 |
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 | |
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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. |
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. |
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. |
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.
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 | |
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Throwable |