java/11 : java.desktop/javax/imageio/spi/ImageReaderSpi.java

ImageReaderSpi
https://openjdk.java.net/
GPLv2 + Classpath Exception
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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: IIORegistry
ImageReader/**
 * The service provider interface (SPI) for {@code ImageReader}s.
 * For more information on service provider classes, see the class comment
 * for the {@code IIORegistry} class.
 *
 * <p> Each {@code ImageReaderSpi} provides several types of information
 * about the {@code ImageReader} 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 getDescription},
 * and {@code 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.
 *
 * <p> Lists of format names, file suffixes, and MIME types associated
 * with the service may be obtained by means of the
 * {@code getFormatNames}, {@code getFileSuffixes}, and
 * {@code getMIMETypes} methods.  These methods may be used to
 * identify candidate {@code ImageReader}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}s
 * are likely to be able to parse a particular data stream is provided
 * by the {@code canDecodeInput} method.  This methods allows the
 * service provider to inspect the actual stream contents.
 *
 * <p> Finally, an instance of the {@code ImageReader} class
 * associated with this service provider may be obtained by calling
 * the {@code 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 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}, to be returned from
     * {@code getInputTypes}.
     * @deprecated Instead of using this field, directly create
     * the equivalent array {@code { ImageInputStream.class }}.
     */
    @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} objects to be returned from
     * {@code getInputTypes}, initially {@code null}.
     */
    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}, initially
     * {@code null}.
     */
    protected String[] writerSpiNames = null;

    The Class of the reader, initially null. /**
     * The {@code Class} of the reader, initially
     * {@code null}.
     */
    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}.  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: IllegalArgumentException – if vendorName is null.
IllegalArgumentException – if version is null.
IllegalArgumentException – if names is null or has length 0.
IllegalArgumentException – if readerClassName is null.
IllegalArgumentException – if inputTypes is null or has length 0./**
     * Constructs an {@code ImageReaderSpi} with a given
     * set of values.
     *
     * @param vendorName the vendor name, as a non-{@code null}
     * {@code String}.
     * @param version a version identifier, as a non-{@code null}
     * {@code String}.
     * @param names a non-{@code null} array of
     * {@code String}s indicating the format names.  At least one
     * entry must be present.
     * @param suffixes an array of {@code String}s indicating the
     * common file suffixes.  If no suffixes are defined,
     * {@code null} should be supplied.  An array of length 0
     * will be normalized to {@code null}.
     * @param MIMETypes an array of {@code String}s indicating
     * the format's MIME types.  If no MIME types are defined,
     * {@code null} should be supplied.  An array of length 0
     * will be normalized to {@code null}.
     * @param readerClassName the fully-qualified name of the
     * associated {@code ImageReader} class, as a
     * non-{@code null String}.
     * @param inputTypes a non-{@code null} array of
     * {@code Class} objects of length at least 1 indicating the
     * legal input types.
     * @param writerSpiNames an array {@code String}s naming the
     * classes of all associated {@code ImageWriter}s, or
     * {@code null}.  An array of length 0 is normalized to
     * {@code null}.
     * @param supportsStandardStreamMetadataFormat a
     * {@code boolean} that indicates whether a stream metadata
     * object can use trees described by the standard metadata format.
     * @param nativeStreamMetadataFormatName a
     * {@code String}, or {@code null}, to be returned from
     * {@code getNativeStreamMetadataFormatName}.
     * @param nativeStreamMetadataFormatClassName a
     * {@code String}, or {@code null}, to be used to instantiate
     * a metadata format object to be returned from
     * {@code getNativeStreamMetadataFormat}.
     * @param extraStreamMetadataFormatNames an array of
     * {@code String}s, or {@code null}, to be returned from
     * {@code getExtraStreamMetadataFormatNames}.  An array of length
     * 0 is normalized to {@code null}.
     * @param extraStreamMetadataFormatClassNames an array of
     * {@code String}s, or {@code null}, to be used to instantiate
     * a metadata format object to be returned from
     * {@code getStreamMetadataFormat}.  An array of length
     * 0 is normalized to {@code null}.
     * @param supportsStandardImageMetadataFormat a
     * {@code boolean} that indicates whether an image metadata
     * object can use trees described by the standard metadata format.
     * @param nativeImageMetadataFormatName a
     * {@code String}, or {@code null}, to be returned from
     * {@code getNativeImageMetadataFormatName}.
     * @param nativeImageMetadataFormatClassName a
     * {@code String}, or {@code null}, to be used to instantiate
     * a metadata format object to be returned from
     * {@code getNativeImageMetadataFormat}.
     * @param extraImageMetadataFormatNames an array of
     * {@code String}s to be returned from
     * {@code getExtraImageMetadataFormatNames}.  An array of length 0
     * is normalized to {@code null}.
     * @param extraImageMetadataFormatClassNames an array of
     * {@code String}s, or {@code null}, to be used to instantiate
     * a metadata format object to be returned from
     * {@code getImageMetadataFormat}.  An array of length
     * 0 is normalized to {@code null}.
     *
     * @exception IllegalArgumentException if {@code vendorName}
     * is {@code null}.
     * @exception IllegalArgumentException if {@code version}
     * is {@code null}.
     * @exception IllegalArgumentException if {@code names}
     * is {@code null} or has length 0.
     * @exception IllegalArgumentException if {@code readerClassName}
     * is {@code null}.
     * @exception IllegalArgumentException if {@code inputTypes}
     * is {@code null} 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 = 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 Class objects of length at least 1./**
     * Returns an array of {@code Class} objects indicating what
     * types of objects may be used as arguments to the reader's
     * {@code setInput} method.
     *
     * <p> For most readers, which only accept input from an
     * {@code ImageInputStream}, a single-element array
     * containing {@code ImageInputStream.class} should be
     * returned.
     *
     * @return a non-{@code null} array of
     * {@code Class} objects of length at least 1.
     */
    public Class<?>[] getInputTypes() {
        return 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: IllegalArgumentException – if source is null.
IOException – if an I/O error occurs while reading the
stream.
Returns: true if it is likely that this stream can be decoded./**
     * Returns {@code true} if the supplied source object appears
     * to be of the format supported by this reader.  Returning
     * {@code 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
     * {@code 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.
     *
     * <p> It is important that the state of the object not be
     * disturbed in order that other {@code ImageReaderSpi}s can
     * properly determine whether they are able to decode the object.
     * In particular, if the source is an
     * {@code ImageInputStream}, a
     * {@code mark}/{@code reset} 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}
     * in order to avoid being invoked in preference to a closer
     * match.
     *
     * <p> If {@code source} is not an instance of one of the
     * classes returned by {@code getInputTypes}, the method
     * should simply return {@code false}.
     *
     * @param source the object (typically an
     * {@code ImageInputStream}) to be decoded.
     *
     * @return {@code true} if it is likely that this stream can
     * be decoded.
     *
     * @exception IllegalArgumentException if {@code source} is
     * {@code null}.
     * @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}
     * implementation associated with this service provider.
     * The returned object will initially be in an initial state
     * as if its {@code reset} method had been called.
     *
     * <p> The default implementation simply returns
     * {@code createReaderInstance(null)}.
     *
     * @return an {@code ImageReader} 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}
     * implementation associated with this service provider.
     * The returned object will initially be in an initial state
     * as if its {@code reset} method had been called.
     *
     * <p> An {@code Object} 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)}.
     *
     * @param extension a plug-in specific extension object, which may
     * be {@code null}.
     *
     * @return an {@code ImageReader} instance.
     *
     * @exception IOException if the attempt to instantiate
     * the reader fails.
     * @exception IllegalArgumentException if the
     * {@code ImageReader}'s constructor throws an
     * {@code IllegalArgumentException} 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: IllegalArgumentException – if reader is null.
Returns: true if reader is recognized./**
     * Returns {@code true} if the {@code ImageReader} object
     * passed in is an instance of the {@code ImageReader}
     * associated with this service provider.
     *
     * <p> The default implementation compares the fully-qualified
     * class name of the {@code reader} 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} instance.
     *
     * @return {@code true} if {@code reader} is recognized.
     *
     * @exception IllegalArgumentException if {@code reader} is
     * {@code null}.
     */
    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: ImageIO.getImageWriter(ImageReader)
Returns: an array of Strings of length at least 1 containing names of ImageWriterSpi, or null./**
     * Returns an array of {@code String}s containing the fully
     * qualified names of all the {@code ImageWriterSpi} classes
     * that can understand the internal metadata representation used
     * by the {@code ImageReader} associated with this service
     * provider, or {@code null} if there are no such
     * {@code ImageWriter}s specified.  If a
     * non-{@code null} 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} returned by
     * {@code ImageIO.getImageWriter(ImageReader)}.
     *
     * <p> This mechanism may be used to obtain
     * {@code ImageWriters} that will understand the internal
     * structure of non-pixel meta-data (see
     * {@code IIOTreeInfo}) generated by an
     * {@code ImageReader}.  By obtaining this data from the
     * {@code ImageReader} and passing it on to one of the
     * {@code 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.
     *
     * @return an array of {@code String}s of length at least 1
     * containing names of {@code ImageWriterSpi}, or
     * {@code null}.
     *
     * @see javax.imageio.ImageIO#getImageWriter(ImageReader)
     */
    public String[] getImageWriterSpiNames() {
        return writerSpiNames == null ?
            null : writerSpiNames.clone();
    }
}
Params:	source – the object (typically an `ImageInputStream`) to be decoded.
Throws:	IllegalArgumentException – if `source` is `null`. IOException – if an I/O error occurs while reading the stream.
Returns:	`true` if it is likely that this stream can be decoded.
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.
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.
Params:	reader – an `ImageReader` instance.
Throws:	IllegalArgumentException – if `reader` is `null`.
Returns:	`true` if `reader` is recognized.
See Also:	ImageIO.getImageWriter(ImageReader)
Returns:	an array of `String`s of length at least 1 containing names of `ImageWriterSpi`, or `null`.
/

java/ 11/ java.desktop/javax/imageio/spi/ImageReaderSpi.java
