javax.imageio
Class ImageIO

java.lang.Object   
  javax.imageio.ImageIO

public final class ImageIO
extends Object   

A class containing static convenience methods for locating ImageReaders and ImageWriters, and performing simple encoding and decoding.

Method Summary

static ImageInputStream	createImageInputStream (Object input) Returns an ImageInputStream that will take its input from the given Object.
static ImageOutputStream	createImageOutputStream (Object output) Returns an ImageOutputStream that will send its output to the given Object.
static File	getCacheDirectory () Returns the current value set by setCacheDirectory, or null if no explicit setting has been made.
static ImageReader	getImageReader (ImageWriter writer) Returns an ImageReadercorresponding to the given ImageWriter, if there is one, or null if the plug-in for this ImageWriter does not specify a corresponding ImageReader, or if the given ImageWriter is not registered.
static Iterator <ImageReader >	getImageReaders (Object input) Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode the supplied Object, typically an ImageInputStream.
static Iterator <ImageReader >	getImageReadersByFormatName (String formatName) Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode the named format.
static Iterator <ImageReader >	getImageReadersByMIMEType (String MIMEType) Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode files with the given MIME type.
static Iterator <ImageReader >	getImageReadersBySuffix (String fileSuffix) Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode files with the given suffix.
static Iterator <ImageTranscoder >	getImageTranscoders (ImageReader reader, ImageWriter writer) Returns an Iterator containing all currently registered ImageTranscoders that claim to be able to transcode between the metadata of the given ImageReader and ImageWriter.
static ImageWriter	getImageWriter (ImageReader reader) Returns an ImageWritercorresponding to the given ImageReader, if there is one, or null if the plug-in for this ImageReader does not specify a corresponding ImageWriter, or if the given ImageReader is not registered.
static Iterator <ImageWriter >	getImageWriters (ImageTypeSpecifier type, String formatName) Returns an Iterator containing all currently registered ImageWriters that claim to be able to encode images of the given layout (specified using an ImageTypeSpecifier) in the given format.
static Iterator <ImageWriter >	getImageWritersByFormatName (String formatName) Returns an Iterator containing all currently registered ImageWriters that claim to be able to encode the named format.
static Iterator <ImageWriter >	getImageWritersByMIMEType (String MIMEType) Returns an Iterator containing all currently registered ImageWriters that claim to be able to encode files with the given MIME type.
static Iterator <ImageWriter >	getImageWritersBySuffix (String fileSuffix) Returns an Iterator containing all currently registered ImageWriters that claim to be able to encode files with the given suffix.
static String []	getReaderFormatNames () Returns an array of Strings listing all of the informal format names understood by the current set of registered readers.
static String []	getReaderMIMETypes () Returns an array of Strings listing all of the MIME types understood by the current set of registered readers.
static boolean	getUseCache () Returns the current value set by setUseCache, or true if no explicit setting has been made.
static String []	getWriterFormatNames () Returns an array of Strings listing all of the informal format names understood by the current set of registered writers.
static String []	getWriterMIMETypes () Returns an array of Strings listing all of the MIME types understood by the current set of registered writers.
static BufferedImage	read (File input) Returns a BufferedImage as the result of decoding a supplied File with an ImageReader chosen automatically from among those currently registered.
static BufferedImage	read (ImageInputStream stream) Returns a BufferedImage as the result of decoding a supplied ImageInputStream with an ImageReader chosen automatically from among those currently registered.
static BufferedImage	read (InputStream input) Returns a BufferedImage as the result of decoding a supplied InputStream with an ImageReader chosen automatically from among those currently registered.
static BufferedImage	read (URL input) Returns a BufferedImage as the result of decoding a supplied URL with an ImageReader chosen automatically from among those currently registered.
static void	scanForPlugins () Scans for plug-ins on the application class path, loads their service provider classes, and registers a service provider instance for each one found with the IIORegistry.
static void	setCacheDirectory (File cacheDirectory) Sets the directory where cache files are to be created.
static void	setUseCache (boolean useCache) Sets a flag indicating whether a disk-based cache file should be used when creating ImageInputStreams and ImageOutputStreams.
static boolean	write (RenderedImage im, String formatName, File output) Writes an image using an arbitrary ImageWriter that supports the given format to a File.
static boolean	write (RenderedImage im, String formatName, ImageOutputStream output) Writes an image using the an arbitrary ImageWriter that supports the given format to an ImageOutputStream.
static boolean	write (RenderedImage im, String formatName, OutputStream output) Writes an image using an arbitrary ImageWriter that supports the given format to an OutputStream.

Methods inherited from class java.lang.Object

clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait

Method Detail

scanForPlugins

public static void scanForPlugins()

Scans for plug-ins on the application class path, loads their service provider classes, and registers a service provider instance for each one found with the IIORegistry.

This method is needed because the application class path can theoretically change, or additional plug-ins may become available. Rather than re-scanning the classpath on every invocation of the API, the class path is scanned automatically only on the first invocation. Clients can call this method to prompt a re-scan. Thus this method need only be invoked by sophisticated applications which dynamically make new plug-ins available at runtime.

The getResources method of the context ClassLoader is used locate JAR files containing files named META-INF/services/javax.imageio.spi.classname, where classname is one of ImageReaderSpi, ImageWriterSpi, ImageTranscoderSpi, ImageInputStreamSpi, or ImageOutputStreamSpi, along the application class path.

The contents of the located files indicate the names of actual implementation classes which implement the aforementioned service provider interfaces; the default class loader is then used to load each of these classes and to instantiate an instance of each class, which is then placed into the registry for later retrieval.

The exact set of locations searched depends on the implementation of the Java runtime enviroment.

See Also:

ClassLoader.getResources(java.lang.String)

setUseCache

public static void setUseCache(boolean useCache)

Sets a flag indicating whether a disk-based cache file should be used when creating ImageInputStreams and ImageOutputStreams.

When reading from a standard InputStream>, it may be necessary to save previously read information in a cache since the underlying stream does not allow data to be re-read. Similarly, when writing to a standard OutputStream, a cache may be used to allow a previously written value to be changed before flushing it to the final destination.

The cache may reside in main memory or on disk. Setting this flag to false disallows the use of disk for future streams, which may be advantageous when working with small images, as the overhead of creating and destroying files is removed.

On startup, the value is set to true.

Parameters:

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

See Also:

getUseCache()

getUseCache

public static boolean getUseCache()

Returns the current value set by setUseCache, or true if no explicit setting has been made.

Returns:

true if a disk-based cache may be used for ImageInputStreams and ImageOutputStreams.

See Also:

setUseCache(boolean)

setCacheDirectory

public static void setCacheDirectory(File    cacheDirectory)

Sets the directory where cache files are to be created. A value of null indicates that the system-dependent default temporary-file directory is to be used. If getUseCache returns false, this value is ignored.

Parameters:

cacheDirectory - a File specifying a directory.

Throws:

SecurityException - if the security manager denies access to the directory.

IllegalArgumentException - if cacheDir is non-null but is not a directory.

See Also:

File.createTempFile(String, String, File) , getCacheDirectory()

getCacheDirectory

public static File    getCacheDirectory()

Returns the current value set by setCacheDirectory, or null if no explicit setting has been made.

Returns:

a File indicating the directory where cache files will be created, or null to indicate the system-dependent default temporary-file directory.

See Also:

setCacheDirectory(java.io.File)

createImageInputStream

public static ImageInputStream    createImageInputStream(Object    input)
                                               throws IOException   

Returns an ImageInputStream that will take its input from the given Object. The set of ImageInputStreamSpis registered with the IIORegistry class is queried and the first one that is able to take input from the supplied object is used to create the returned ImageInputStream. If no suitable ImageInputStreamSpi exists, null is returned.

The current cache settings from getUseCacheand getCacheDirectory will be used to control caching.

Parameters:

input - an Object to be used as an input source, such as a File, readable RandomAccessFile, or InputStream.

Returns:

an ImageInputStream, or null.

Throws:

IllegalArgumentException - if input is null.

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

See Also:

ImageInputStreamSpi

createImageOutputStream

public static ImageOutputStream    createImageOutputStream(Object    output)
                                                 throws IOException   

Returns an ImageOutputStream that will send its output to the given Object. The set of ImageOutputStreamSpis registered with the IIORegistry class is queried and the first one that is able to send output from the supplied object is used to create the returned ImageOutputStream. If no suitable ImageOutputStreamSpi exists, null is returned.

The current cache settings from getUseCacheand getCacheDirectory will be used to control caching.

Parameters:

output - an Object to be used as an output destination, such as a File, writable RandomAccessFile, or OutputStream.

Returns:

an ImageOutputStream, or null.

Throws:

IllegalArgumentException - if output is null.

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

See Also:

ImageOutputStreamSpi

getReaderFormatNames

public static String   [] getReaderFormatNames()

Returns an array of Strings listing all of the informal format names understood by the current set of registered readers.

Returns:

an array of Strings.

getReaderMIMETypes

public static String   [] getReaderMIMETypes()

Returns an array of Strings listing all of the MIME types understood by the current set of registered readers.

Returns:

an array of Strings.

getImageReaders

public static Iterator   <ImageReader   > getImageReaders(Object    input)

Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode the supplied Object, typically an ImageInputStream.

The stream position is left at its prior position upon exit from this method.

Parameters:

input - an ImageInputStream or other Object containing encoded image data.

Returns:

an Iterator containing ImageReaders.

Throws:

IllegalArgumentException - if input is null.

See Also:

ImageReaderSpi.canDecodeInput(java.lang.Object)

getImageReadersByFormatName

public static Iterator   <ImageReader   > getImageReadersByFormatName(String    formatName)

Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode the named format.

Parameters:

formatName - a String containing the informal name of a format (e.g., "jpeg" or "tiff".

Returns:

an Iterator containing ImageReaders.

Throws:

IllegalArgumentException - if formatName is null.

See Also:

ImageReaderWriterSpi.getFormatNames()

getImageReadersBySuffix

public static Iterator   <ImageReader   > getImageReadersBySuffix(String    fileSuffix)

Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode files with the given suffix.

Parameters:

fileSuffix - a String containing a file suffix (e.g., "jpg" or "tiff").

Returns:

an Iterator containing ImageReaders.

Throws:

IllegalArgumentException - if fileSuffix is null.

See Also:

ImageReaderWriterSpi.getFileSuffixes()

getImageReadersByMIMEType

public static Iterator   <ImageReader   > getImageReadersByMIMEType(String    MIMEType)

Returns an Iterator containing all currently registered ImageReaders that claim to be able to decode files with the given MIME type.

Parameters:

MIMEType - a String containing a file suffix (e.g., "image/jpeg" or "image/x-bmp").

Returns:

an Iterator containing ImageReaders.

Throws:

IllegalArgumentException - if MIMEType is null.

See Also:

ImageReaderWriterSpi.getMIMETypes()

getWriterFormatNames