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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}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
* {@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 {@code Class} objects to be returned from
* {@code getInputTypes}, initially {@code null}.
*/
protected Class<?>[] inputTypes = null;
/**
* An array of strings to be returned from
* {@code getImageWriterSpiNames}, initially
* {@code null}.
*/
protected String[] writerSpiNames = null;
/**
* The {@code Class} of the reader, initially
* {@code null}.
*/
private Class<?> readerClass = null;
/**
* 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 {@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 {@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 {@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 {@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 {@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 {@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 {@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();
}
}