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package javax.imageio.spi;

import java.io.IOException;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;

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

Each ImageReaderSpi provides several types of information about the ImageReader class with which it is associated.

The name of the vendor who defined the SPI class and a brief description of the class are available via the getVendorName, getDescription, and getVersion methods. These methods may be internationalized to provide locale-specific output. These methods are intended mainly to provide short, human-readable information that might be used to organize a pop-up menu or other list.

Lists of format names, file suffixes, and MIME types associated with the service may be obtained by means of the getFormatNames, getFileSuffixes, and getMIMETypes methods. These methods may be used to identify candidate ImageReaders for decoding a particular file or stream based on manual format selection, file naming, or MIME associations (for example, when accessing a file over HTTP or as an email attachment).

A more reliable way to determine which ImageReaders are likely to be able to parse a particular data stream is provided by the canDecodeInput method. This methods allows the service provider to inspect the actual stream contents.

Finally, an instance of the ImageReader class associated with this service provider may be obtained by calling the createReaderInstance method. Any heavyweight initialization, such as the loading of native libraries or creation of large tables, should be deferred at least until the first invocation of this method.

See Also:
/** * The service provider interface (SPI) for <code>ImageReader</code>s. * For more information on service provider classes, see the class comment * for the <code>IIORegistry</code> class. * * <p> Each <code>ImageReaderSpi</code> provides several types of information * about the <code>ImageReader</code> class with which it is associated. * * <p> The name of the vendor who defined the SPI class and a * brief description of the class are available via the * <code>getVendorName</code>, <code>getDescription</code>, * and <code>getVersion</code> methods. * These methods may be internationalized to provide locale-specific * output. These methods are intended mainly to provide short, * human-readable information that might be used to organize a pop-up * menu or other list. * * <p> Lists of format names, file suffixes, and MIME types associated * with the service may be obtained by means of the * <code>getFormatNames</code>, <code>getFileSuffixes</code>, and * <code>getMIMETypes</code> methods. These methods may be used to * identify candidate <code>ImageReader</code>s for decoding a * particular file or stream based on manual format selection, file * naming, or MIME associations (for example, when accessing a file * over HTTP or as an email attachment). * * <p> A more reliable way to determine which <code>ImageReader</code>s * are likely to be able to parse a particular data stream is provided * by the <code>canDecodeInput</code> method. This methods allows the * service provider to inspect the actual stream contents. * * <p> Finally, an instance of the <code>ImageReader</code> class * associated with this service provider may be obtained by calling * the <code>createReaderInstance</code> method. Any heavyweight * initialization, such as the loading of native libraries or creation * of large tables, should be deferred at least until the first * invocation of this method. * * @see IIORegistry * @see javax.imageio.ImageReader * */
public abstract class ImageReaderSpi extends ImageReaderWriterSpi {
A single-element array, initially containing ImageInputStream.class, to be returned from getInputTypes.
Deprecated:Instead of using this field, directly create the equivalent array { ImageInputStream.class }.
/** * A single-element array, initially containing * <code>ImageInputStream.class</code>, to be returned from * <code>getInputTypes</code>. * @deprecated Instead of using this field, directly create * the equivalent array <code>{ ImageInputStream.class }<code>. */
@Deprecated public static final Class[] STANDARD_INPUT_TYPE = { ImageInputStream.class };
An array of Class objects to be returned from getInputTypes, initially null.
/** * An array of <code>Class</code> objects to be returned from * <code>getInputTypes</code>, initially <code>null</code>. */
protected Class[] inputTypes = null;
An array of strings to be returned from getImageWriterSpiNames, initially null.
/** * An array of strings to be returned from * <code>getImageWriterSpiNames</code>, initially * <code>null</code>. */
protected String[] writerSpiNames = null;
The Class of the reader, initially null.
/** * The <code>Class</code> of the reader, initially * <code>null</code>. */
private Class readerClass = null;
Constructs a blank ImageReaderSpi. It is up to the subclass to initialize instance variables and/or override method implementations in order to provide working versions of all methods.
/** * Constructs a blank <code>ImageReaderSpi</code>. It is up to * the subclass to initialize instance variables and/or override * method implementations in order to provide working versions of * all methods. */
protected ImageReaderSpi() { }
Constructs an ImageReaderSpi with a given set of values.
Params:
  • vendorName – the vendor name, as a non-null String.
  • version – a version identifier, as a non-null String.
  • names – a non-null array of Strings indicating the format names. At least one entry must be present.
  • suffixes – an array of Strings indicating the common file suffixes. If no suffixes are defined, null should be supplied. An array of length 0 will be normalized to null.
  • MIMETypes – an array of Strings indicating the format's MIME types. If no MIME types are defined, null should be supplied. An array of length 0 will be normalized to null.
  • readerClassName – the fully-qualified name of the associated ImageReader class, as a non-null String.
  • inputTypes – a non-null array of Class objects of length at least 1 indicating the legal input types.
  • writerSpiNames – an array Strings naming the classes of all associated ImageWriters, or null. An array of length 0 is normalized to null.
  • supportsStandardStreamMetadataFormat – a boolean that indicates whether a stream metadata object can use trees described by the standard metadata format.
  • nativeStreamMetadataFormatName – a String, or null, to be returned from getNativeStreamMetadataFormatName.
  • nativeStreamMetadataFormatClassName – a String, or null, to be used to instantiate a metadata format object to be returned from getNativeStreamMetadataFormat.
  • extraStreamMetadataFormatNames – an array of Strings, or null, to be returned from getExtraStreamMetadataFormatNames. An array of length 0 is normalized to null.
  • extraStreamMetadataFormatClassNames – an array of Strings, or null, to be used to instantiate a metadata format object to be returned from getStreamMetadataFormat. An array of length 0 is normalized to null.
  • supportsStandardImageMetadataFormat – a boolean that indicates whether an image metadata object can use trees described by the standard metadata format.
  • nativeImageMetadataFormatName – a String, or null, to be returned from getNativeImageMetadataFormatName.
  • nativeImageMetadataFormatClassName – a String, or null, to be used to instantiate a metadata format object to be returned from getNativeImageMetadataFormat.
  • extraImageMetadataFormatNames – an array of Strings to be returned from getExtraImageMetadataFormatNames. An array of length 0 is normalized to null.
  • extraImageMetadataFormatClassNames – an array of Strings, or null, to be used to instantiate a metadata format object to be returned from getImageMetadataFormat. An array of length 0 is normalized to null.
Throws:
/** * Constructs an <code>ImageReaderSpi</code> with a given * set of values. * * @param vendorName the vendor name, as a non-<code>null</code> * <code>String</code>. * @param version a version identifier, as a non-<code>null</code> * <code>String</code>. * @param names a non-<code>null</code> array of * <code>String</code>s indicating the format names. At least one * entry must be present. * @param suffixes an array of <code>String</code>s indicating the * common file suffixes. If no suffixes are defined, * <code>null</code> should be supplied. An array of length 0 * will be normalized to <code>null</code>. * @param MIMETypes an array of <code>String</code>s indicating * the format's MIME types. If no MIME types are defined, * <code>null</code> should be supplied. An array of length 0 * will be normalized to <code>null</code>. * @param readerClassName the fully-qualified name of the * associated <code>ImageReader</code> class, as a * non-<code>null</code> <code>String</code>. * @param inputTypes a non-<code>null</code> array of * <code>Class</code> objects of length at least 1 indicating the * legal input types. * @param writerSpiNames an array <code>String</code>s naming the * classes of all associated <code>ImageWriter</code>s, or * <code>null</code>. An array of length 0 is normalized to * <code>null</code>. * @param supportsStandardStreamMetadataFormat a * <code>boolean</code> that indicates whether a stream metadata * object can use trees described by the standard metadata format. * @param nativeStreamMetadataFormatName a * <code>String</code>, or <code>null</code>, to be returned from * <code>getNativeStreamMetadataFormatName</code>. * @param nativeStreamMetadataFormatClassName a * <code>String</code>, or <code>null</code>, to be used to instantiate * a metadata format object to be returned from * <code>getNativeStreamMetadataFormat</code>. * @param extraStreamMetadataFormatNames an array of * <code>String</code>s, or <code>null</code>, to be returned from * <code>getExtraStreamMetadataFormatNames</code>. An array of length * 0 is normalized to <code>null</code>. * @param extraStreamMetadataFormatClassNames an array of * <code>String</code>s, or <code>null</code>, to be used to instantiate * a metadata format object to be returned from * <code>getStreamMetadataFormat</code>. An array of length * 0 is normalized to <code>null</code>. * @param supportsStandardImageMetadataFormat a * <code>boolean</code> that indicates whether an image metadata * object can use trees described by the standard metadata format. * @param nativeImageMetadataFormatName a * <code>String</code>, or <code>null</code>, to be returned from * <code>getNativeImageMetadataFormatName</code>. * @param nativeImageMetadataFormatClassName a * <code>String</code>, or <code>null</code>, to be used to instantiate * a metadata format object to be returned from * <code>getNativeImageMetadataFormat</code>. * @param extraImageMetadataFormatNames an array of * <code>String</code>s to be returned from * <code>getExtraImageMetadataFormatNames</code>. An array of length 0 * is normalized to <code>null</code>. * @param extraImageMetadataFormatClassNames an array of * <code>String</code>s, or <code>null</code>, to be used to instantiate * a metadata format object to be returned from * <code>getImageMetadataFormat</code>. An array of length * 0 is normalized to <code>null</code>. * * @exception IllegalArgumentException if <code>vendorName</code> * is <code>null</code>. * @exception IllegalArgumentException if <code>version</code> * is <code>null</code>. * @exception IllegalArgumentException if <code>names</code> * is <code>null</code> or has length 0. * @exception IllegalArgumentException if <code>readerClassName</code> * is <code>null</code>. * @exception IllegalArgumentException if <code>inputTypes</code> * is <code>null</code> or has length 0. */
public ImageReaderSpi(String vendorName, String version, String[] names, String[] suffixes, String[] MIMETypes, String readerClassName, Class[] inputTypes, String[] writerSpiNames, boolean supportsStandardStreamMetadataFormat, String nativeStreamMetadataFormatName, String nativeStreamMetadataFormatClassName, String[] extraStreamMetadataFormatNames, String[] extraStreamMetadataFormatClassNames, boolean supportsStandardImageMetadataFormat, String nativeImageMetadataFormatName, String nativeImageMetadataFormatClassName, String[] extraImageMetadataFormatNames, String[] extraImageMetadataFormatClassNames) { super(vendorName, version, names, suffixes, MIMETypes, readerClassName, supportsStandardStreamMetadataFormat, nativeStreamMetadataFormatName, nativeStreamMetadataFormatClassName, extraStreamMetadataFormatNames, extraStreamMetadataFormatClassNames, supportsStandardImageMetadataFormat, nativeImageMetadataFormatName, nativeImageMetadataFormatClassName, extraImageMetadataFormatNames, extraImageMetadataFormatClassNames); if (inputTypes == null) { throw new IllegalArgumentException ("inputTypes == null!"); } if (inputTypes.length == 0) { throw new IllegalArgumentException ("inputTypes.length == 0!"); } this.inputTypes = (inputTypes == STANDARD_INPUT_TYPE) ? new Class<?>[] { ImageInputStream.class } : inputTypes.clone(); // If length == 0, leave it null if (writerSpiNames != null && writerSpiNames.length > 0) { this.writerSpiNames = (String[])writerSpiNames.clone(); } }
Returns an array of Class objects indicating what types of objects may be used as arguments to the reader's setInput method.

For most readers, which only accept input from an ImageInputStream, a single-element array containing ImageInputStream.class should be returned.

Returns:a non-null array of Classobjects of length at least 1.
/** * Returns an array of <code>Class</code> objects indicating what * types of objects may be used as arguments to the reader's * <code>setInput</code> method. * * <p> For most readers, which only accept input from an * <code>ImageInputStream</code>, a single-element array * containing <code>ImageInputStream.class</code> should be * returned. * * @return a non-<code>null</code> array of * <code>Class</code>objects of length at least 1. */
public Class[] getInputTypes() { return (Class[])inputTypes.clone(); }
Returns true if the supplied source object appears to be of the format supported by this reader. Returning true from this method does not guarantee that reading will succeed, only that there appears to be a reasonable chance of success based on a brief inspection of the stream contents. If the source is an ImageInputStream, implementations will commonly check the first several bytes of the stream for a "magic number" associated with the format. Once actual reading has commenced, the reader may still indicate failure at any time prior to the completion of decoding.

It is important that the state of the object not be disturbed in order that other ImageReaderSpis can properly determine whether they are able to decode the object. In particular, if the source is an ImageInputStream, a mark/reset pair should be used to preserve the stream position.

Formats such as "raw," which can potentially attempt to read nearly any stream, should return false in order to avoid being invoked in preference to a closer match.

If source is not an instance of one of the classes returned by getInputTypes, the method should simply return false.

Params:
  • source – the object (typically an ImageInputStream) to be decoded.
Throws:
Returns:true if it is likely that this stream can be decoded.
/** * Returns <code>true</code> if the supplied source object appears * to be of the format supported by this reader. Returning * <code>true</code> from this method does not guarantee that * reading will succeed, only that there appears to be a * reasonable chance of success based on a brief inspection of the * stream contents. If the source is an * <code>ImageInputStream</code>, implementations will commonly * check the first several bytes of the stream for a "magic * number" associated with the format. Once actual reading has * commenced, the reader may still indicate failure at any time * prior to the completion of decoding. * * <p> It is important that the state of the object not be * disturbed in order that other <code>ImageReaderSpi</code>s can * properly determine whether they are able to decode the object. * In particular, if the source is an * <code>ImageInputStream</code>, a * <code>mark</code>/<code>reset</code> pair should be used to * preserve the stream position. * * <p> Formats such as "raw," which can potentially attempt * to read nearly any stream, should return <code>false</code> * in order to avoid being invoked in preference to a closer * match. * * <p> If <code>source</code> is not an instance of one of the * classes returned by <code>getInputTypes</code>, the method * should simply return <code>false</code>. * * @param source the object (typically an * <code>ImageInputStream</code>) to be decoded. * * @return <code>true</code> if it is likely that this stream can * be decoded. * * @exception IllegalArgumentException if <code>source</code> is * <code>null</code>. * @exception IOException if an I/O error occurs while reading the * stream. */
public abstract boolean canDecodeInput(Object source) throws IOException;
Returns an instance of the ImageReader implementation associated with this service provider. The returned object will initially be in an initial state as if its reset method had been called.

The default implementation simply returns createReaderInstance(null).

Throws:
  • IOException – if an error occurs during loading, or initialization of the reader class, or during instantiation or initialization of the reader object.
Returns:an ImageReader instance.
/** * Returns an instance of the <code>ImageReader</code> * implementation associated with this service provider. * The returned object will initially be in an initial state * as if its <code>reset</code> method had been called. * * <p> The default implementation simply returns * <code>createReaderInstance(null)</code>. * * @return an <code>ImageReader</code> instance. * * @exception IOException if an error occurs during loading, * or initialization of the reader class, or during instantiation * or initialization of the reader object. */
public ImageReader createReaderInstance() throws IOException { return createReaderInstance(null); }
Returns an instance of the ImageReader implementation associated with this service provider. The returned object will initially be in an initial state as if its reset method had been called.

An Object may be supplied to the plug-in at construction time. The nature of the object is entirely plug-in specific.

Typically, a plug-in will implement this method using code such as return new MyImageReader(this).

Params:
  • extension – a plug-in specific extension object, which may be null.
Throws:
  • IOException – if the attempt to instantiate the reader fails.
  • IllegalArgumentException – if the ImageReader's constructor throws an IllegalArgumentException to indicate that the extension object is unsuitable.
Returns:an ImageReader instance.
/** * Returns an instance of the <code>ImageReader</code> * implementation associated with this service provider. * The returned object will initially be in an initial state * as if its <code>reset</code> method had been called. * * <p> An <code>Object</code> may be supplied to the plug-in at * construction time. The nature of the object is entirely * plug-in specific. * * <p> Typically, a plug-in will implement this method using code * such as <code>return new MyImageReader(this)</code>. * * @param extension a plug-in specific extension object, which may * be <code>null</code>. * * @return an <code>ImageReader</code> instance. * * @exception IOException if the attempt to instantiate * the reader fails. * @exception IllegalArgumentException if the * <code>ImageReader</code>'s constructor throws an * <code>IllegalArgumentException</code> to indicate that the * extension object is unsuitable. */
public abstract ImageReader createReaderInstance(Object extension) throws IOException;
Returns true if the ImageReader object passed in is an instance of the ImageReader associated with this service provider.

The default implementation compares the fully-qualified class name of the reader argument with the class name passed into the constructor. This method may be overridden if more sophisticated checking is required.

Params:
  • reader – an ImageReader instance.
Throws:
Returns:true if reader is recognized.
/** * Returns <code>true</code> if the <code>ImageReader</code> object * passed in is an instance of the <code>ImageReader</code> * associated with this service provider. * * <p> The default implementation compares the fully-qualified * class name of the <code>reader</code> argument with the class * name passed into the constructor. This method may be overridden * if more sophisticated checking is required. * * @param reader an <code>ImageReader</code> instance. * * @return <code>true</code> if <code>reader</code> is recognized. * * @exception IllegalArgumentException if <code>reader</code> is * <code>null</code>. */
public boolean isOwnReader(ImageReader reader) { if (reader == null) { throw new IllegalArgumentException("reader == null!"); } String name = reader.getClass().getName(); return name.equals(pluginClassName); }
Returns an array of Strings containing the fully qualified names of all the ImageWriterSpi classes that can understand the internal metadata representation used by the ImageReader associated with this service provider, or null if there are no such ImageWriters specified. If a non-null value is returned, it must have non-zero length.

The first item in the array must be the name of the service provider for the "preferred" writer, as it will be used to instantiate the ImageWriter returned by ImageIO.getImageWriter(ImageReader).

This mechanism may be used to obtain ImageWriters that will understand the internal structure of non-pixel meta-data (see IIOTreeInfo) generated by an ImageReader. By obtaining this data from the ImageReader and passing it on to one of the ImageWriters obtained with this method, a client program can read an image, modify it in some way, and write it back out while preserving all meta-data, without having to understand anything about the internal structure of the meta-data, or even about the image format.

See Also:
Returns:an array of Strings of length at least 1 containing names of ImageWriterSpi, or null.
/** * Returns an array of <code>String</code>s containing the fully * qualified names of all the <code>ImageWriterSpi</code> classes * that can understand the internal metadata representation used * by the <code>ImageReader</code> associated with this service * provider, or <code>null</code> if there are no such * <code>ImageWriter</code>s specified. If a * non-<code>null</code> value is returned, it must have non-zero * length. * * <p> The first item in the array must be the name of the service * provider for the "preferred" writer, as it will be used to * instantiate the <code>ImageWriter</code> returned by * <code>ImageIO.getImageWriter(ImageReader)</code>. * * <p> This mechanism may be used to obtain * <code>ImageWriters</code> that will understand the internal * structure of non-pixel meta-data (see * <code>IIOTreeInfo</code>) generated by an * <code>ImageReader</code>. By obtaining this data from the * <code>ImageReader</code> and passing it on to one of the * <code>ImageWriters</code> obtained with this method, a client * program can read an image, modify it in some way, and write it * back out while preserving all meta-data, without having to * understand anything about the internal structure of the * meta-data, or even about the image format. * * @return an array of <code>String</code>s of length at least 1 * containing names of <code>ImageWriterSpi</code>, or * <code>null</code>. * * @see javax.imageio.ImageIO#getImageWriter(ImageReader) */
public String[] getImageWriterSpiNames() { return writerSpiNames == null ? null : (String[])writerSpiNames.clone(); } }