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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 <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
* <code>ImageInputStream.class</code>, to be returned from
* <code>getInputTypes</code>.
*/
public static final Class[] STANDARD_INPUT_TYPE =
{ ImageInputStream.class };
/**
* 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
* <code>getImageWriterSpiNames</code>, initially
* <code>null</code>.
*/
protected String[] writerSpiNames = null;
/**
* The <code>Class</code> of the reader, initially
* <code>null</code>.
*/
private Class readerClass = null;
/**
* 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 <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 <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 <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 <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 <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 contructor throws an
* <code>IllegalArgumentException</code> to indicate that the
* extension object is unsuitable.
*/
public abstract ImageReader createReaderInstance(Object extension)
throws IOException;
/**
* 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 <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();
}
}