javax.imageio.spi
class ImageOutputStreamSpi

java.lang.Object javax.imageio.spi.IIOServiceProvider javax.imageio.spi.ImageOutputStreamSpi

All Implemented Interfaces:

RegisterableService

public abstract class ImageOutputStreamSpi
extends IIOServiceProvider

The service provider interface (SPI) for ImageOutputStreams. For more information on service provider interfaces, see the class comment for the IIORegistry class.

This interface allows arbitrary objects to be "wrapped" by instances of ImageOutputStream. For example, a particular ImageOutputStreamSpi might allow a generic OutputStream to be used as a destination; another might output to a File or to a device such as a serial port.

By treating the creation of ImageOutputStreams as a pluggable service, it becomes possible to handle future output destinations without changing the API. Also, high-performance implementations of ImageOutputStream (for example, native implementations for a particular platform) can be installed and used transparently by applications.

outputClass

protected Class outputClass

A Class object indicating the legal object type for use by the createInputStreamInstance method.

ImageOutputStreamSpi

protected ImageOutputStreamSpi()

Constructs a blank ImageOutputStreamSpi. It is up to the subclass to initialize instance variables and/or override method implementations in order to provide working versions of all methods.

ImageOutputStreamSpi

public ImageOutputStreamSpi(String vendorName,
                            String version,
                            Class outputClass)

Constructs an ImageOutputStreamSpi with a given set of values.

Parameters:

vendorName - the vendor name.

version - a version identifier.

outputClass - a Class object indicating the legal object type for use by the createOutputStreamInstance method.

canUseCacheFile

public boolean canUseCacheFile()

Returns true if the ImageOutputStream implementation associated with this service provider can optionally make use of a cache File for improved performance and/or memory footrprint. If false, the value of the cacheFile argument to createOutputStreamInstance will be ignored.

The default implementation returns false.

Returns:

true if a cache file can be used by the output streams created by this service provider.

createOutputStreamInstance

public ImageOutputStream createOutputStreamInstance(Object output)
                                             throws IOException

Returns an instance of the ImageOutputStream implementation associated with this service provider. A cache file will be created in the system-dependent default temporary-file directory, if needed.

Parameters:

output - an object of the class type returned by getOutputClass.

Returns:

an ImageOutputStream instance.

Throws:

IOException - if a cache file is needed but cannot be created.

createOutputStreamInstance

public abstract ImageOutputStream createOutputStreamInstance(Object output,
                                                             boolean useCache,
                                                             File cacheDir)
                                                      throws IOException

Returns an instance of the ImageOutputStream implementation associated with this service provider. If the use of a cache file is optional, the useCache parameter will be consulted. Where a cache is required, or not applicable, the value of useCache will be ignored.

Parameters:

output - an object of the class type returned by getOutputClass.

useCache - a boolean indicating whether a cache file should be used, in cases where it is optional.

cacheDir - a File indicating where the cache file should be created, or null to use the system directory.

Returns:

an ImageOutputStream instance.

Throws:

IOException - if a cache file is needed but cannot be created.

getOutputClass

public Class getOutputClass()

Returns a Class object representing the class or interface type that must be implemented by an output destination in order to be "wrapped" in an ImageOutputStream via the createOutputStreamInstance method.

Typical return values might include OutputStream.class or File.class, but any class may be used.

Returns:

a Class variable.

needsCacheFile

public boolean needsCacheFile()

Returns true if the ImageOutputStream implementation associated with this service provider requires the use of a cache File.

The default implementation returns false.

Returns:

true if a cache file is needed by the output streams created by this service provider.