javax.imageio.spi

Class 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.

    See Also:
    IIORegistry, ImageOutputStream

    • Field Detail

      • outputClass

        protected Class<?> outputClass
        A Class object indicating the legal object type for use by the createInputStreamInstance method.

    • Constructor Detail

      • 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.
        Throws:
        IllegalArgumentException - if vendorName is null.
        IllegalArgumentException - if version is null.

    • Method Detail

      • 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.
        See Also:
        createOutputStreamInstance(Object, boolean, File)

      • 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.

      • 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.

      • 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:
        IllegalArgumentException - if output is not an instance of the correct class or is null.
        IllegalArgumentException - if a cache file is needed, but cacheDir is non- null and is not a directory.
        IOException - if a cache file is needed but cannot be created.
        See Also:
        getOutputClass()

      • 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:
        IllegalArgumentException - if output is not an instance of the correct class or is null.
        IOException - if a cache file is needed but cannot be created.
        See Also:
        getOutputClass()