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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.

/**
     * 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 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 contructor 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 contructor 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();
    }
}