RegisterableService
public abstract class ImageReaderSpi extends ImageReaderWriterSpi
ImageReader
s. 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 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).
A more reliable way to determine which ImageReader
s 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.
Modifier and Type | Field | Description |
---|---|---|
protected Class<?>[] |
inputTypes |
An array of Class objects to be returned from getInputTypes , initially null . |
static final Class<?>[] |
STANDARD_INPUT_TYPE |
Deprecated. |
protected String[] |
writerSpiNames |
An array of strings to be returned from getImageWriterSpiNames , initially null . |
extraImageMetadataFormatClassNames, extraImageMetadataFormatNames, extraStreamMetadataFormatClassNames, extraStreamMetadataFormatNames, MIMETypes, names, nativeImageMetadataFormatClassName, nativeImageMetadataFormatName, nativeStreamMetadataFormatClassName, nativeStreamMetadataFormatName, pluginClassName, suffixes, supportsStandardImageMetadataFormat, supportsStandardStreamMetadataFormat
vendorName, version
Modifier | Constructor | Description |
---|---|---|
protected |
Constructs a blank ImageReaderSpi . |
|
Constructs an ImageReaderSpi with a given set of values. |
Modifier and Type | Method | Description |
---|---|---|
abstract boolean |
canDecodeInput |
Returns true if the supplied source object appears to be of the format supported by this reader. |
ImageReader |
createReaderInstance() |
Returns an instance of the ImageReader implementation associated with this service provider. |
abstract ImageReader |
createReaderInstance |
Returns an instance of the ImageReader implementation associated with this service provider. |
String[] |
getImageWriterSpiNames() |
Returns an array of String s 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 ImageWriter s specified. |
Class<?>[] |
getInputTypes() |
Returns an array of Class objects indicating what types of objects may be used as arguments to the reader's setInput method. |
boolean |
isOwnReader |
Returns true if the ImageReader object passed in is an instance of the ImageReader associated with this service provider. |
getExtraImageMetadataFormatNames, getExtraStreamMetadataFormatNames, getFileSuffixes, getFormatNames, getImageMetadataFormat, getMIMETypes, getNativeImageMetadataFormatName, getNativeStreamMetadataFormatName, getPluginClassName, getStreamMetadataFormat, isStandardImageMetadataFormatSupported, isStandardStreamMetadataFormatSupported
getDescription, getVendorName, getVersion, onDeregistration, onRegistration
@Deprecated public static final Class<?>[] STANDARD_INPUT_TYPE
{ ImageInputStream.class }
.ImageInputStream.class
, to be returned from getInputTypes
.protected Class<?>[] inputTypes
Class
objects to be returned from getInputTypes
, initially null
.protected String[] writerSpiNames
getImageWriterSpiNames
, initially null
.protected ImageReaderSpi()
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.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)
ImageReaderSpi
with a given set of values.vendorName
- the vendor name, as a non-null
String
.version
- a version identifier, as a non-null
String
.names
- a non-null
array of String
s indicating the format names. At least one entry must be present.suffixes
- an array of String
s 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 String
s 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 String
s naming the classes of all associated ImageWriter
s, 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 String
s, or null
, to be returned from getExtraStreamMetadataFormatNames
. An array of length 0 is normalized to null
.extraStreamMetadataFormatClassNames
- an array of String
s, 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 String
s to be returned from getExtraImageMetadataFormatNames
. An array of length 0 is normalized to null
.extraImageMetadataFormatClassNames
- an array of String
s, 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
.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.public Class<?>[] getInputTypes()
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.
null
array of Class
objects of length at least 1.public abstract boolean canDecodeInput(Object source) throws IOException
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 ImageReaderSpi
s 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
.
source
- the object (typically an ImageInputStream
) to be decoded.true
if it is likely that this stream can be decoded.IllegalArgumentException
- if source
is null
.IOException
- if an I/O error occurs while reading the stream.public ImageReader createReaderInstance() throws IOException
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)
.
ImageReader
instance.IOException
- if an error occurs during loading, or initialization of the reader class, or during instantiation or initialization of the reader object.public abstract ImageReader createReaderInstance(Object extension) throws IOException
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)
.
extension
- a plug-in specific extension object, which may be null
.ImageReader
instance.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.public boolean isOwnReader(ImageReader reader)
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.
reader
- an ImageReader
instance.true
if reader
is recognized.IllegalArgumentException
- if reader
is null
.public String[] getImageWriterSpiNames()
String
s 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 ImageWriter
s 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.
String
s of length at least 1 containing names of ImageWriterSpi
, or null
.
© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/javax/imageio/spi/ImageReaderSpi.html
{ ImageInputStream.class }
.