- java.lang.Object
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- javax.imageio.spi.IIOServiceProvider
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- javax.imageio.spi.ImageReaderWriterSpi
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- javax.imageio.spi.ImageReaderSpi
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- All Implemented Interfaces:
RegisterableService
public abstract class ImageReaderSpi extends ImageReaderWriterSpi
The service provider interface (SPI) forImageReaders. For more information on service provider classes, see the class comment for theIIORegistryclass.Each
ImageReaderSpiprovides several types of information about theImageReaderclass 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, andgetVersionmethods. 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, andgetMIMETypesmethods. These methods may be used to identify candidateImageReaders 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 thecanDecodeInputmethod. This methods allows the service provider to inspect the actual stream contents.Finally, an instance of the
ImageReaderclass associated with this service provider may be obtained by calling thecreateReaderInstancemethod. 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
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Field Summary
Fields Modifier and Type Field Description protected Class<?>[]inputTypesAn array ofClassobjects to be returned fromgetInputTypes, initiallynull.static Class<?>[]STANDARD_INPUT_TYPEDeprecated.Instead of using this field, directly create the equivalent array{ ImageInputStream.class }.protected String[]writerSpiNamesAn array of strings to be returned fromgetImageWriterSpiNames, initiallynull.-
Fields declared in class javax.imageio.spi.ImageReaderWriterSpi
extraImageMetadataFormatClassNames, extraImageMetadataFormatNames, extraStreamMetadataFormatClassNames, extraStreamMetadataFormatNames, MIMETypes, names, nativeImageMetadataFormatClassName, nativeImageMetadataFormatName, nativeStreamMetadataFormatClassName, nativeStreamMetadataFormatName, pluginClassName, suffixes, supportsStandardImageMetadataFormat, supportsStandardStreamMetadataFormat
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Fields declared in class javax.imageio.spi.IIOServiceProvider
vendorName, version
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Constructor Summary
Constructors Modifier Constructor Description protectedImageReaderSpi()Constructs a blankImageReaderSpi.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)Constructs anImageReaderSpiwith a given set of values.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description abstract booleancanDecodeInput(Object source)Returnstrueif the supplied source object appears to be of the format supported by this reader.ImageReadercreateReaderInstance()Returns an instance of theImageReaderimplementation associated with this service provider.abstract ImageReadercreateReaderInstance(Object extension)Returns an instance of theImageReaderimplementation associated with this service provider.String[]getImageWriterSpiNames()Returns an array ofStrings containing the fully qualified names of all theImageWriterSpiclasses that can understand the internal metadata representation used by theImageReaderassociated with this service provider, ornullif there are no suchImageWriters specified.Class<?>[]getInputTypes()Returns an array ofClassobjects indicating what types of objects may be used as arguments to the reader'ssetInputmethod.booleanisOwnReader(ImageReader reader)Returnstrueif theImageReaderobject passed in is an instance of theImageReaderassociated with this service provider.-
Methods declared in class javax.imageio.spi.ImageReaderWriterSpi
getExtraImageMetadataFormatNames, getExtraStreamMetadataFormatNames, getFileSuffixes, getFormatNames, getImageMetadataFormat, getMIMETypes, getNativeImageMetadataFormatName, getNativeStreamMetadataFormatName, getPluginClassName, getStreamMetadataFormat, isStandardImageMetadataFormatSupported, isStandardStreamMetadataFormatSupported
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Methods declared in class javax.imageio.spi.IIOServiceProvider
getDescription, getVendorName, getVersion, onDeregistration, onRegistration
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Field Detail
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STANDARD_INPUT_TYPE
@Deprecated public static final Class<?>[] STANDARD_INPUT_TYPE
Deprecated.Instead of using this field, directly create the equivalent array{ ImageInputStream.class }.A single-element array, initially containingImageInputStream.class, to be returned fromgetInputTypes.
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inputTypes
protected Class<?>[] inputTypes
An array ofClassobjects to be returned fromgetInputTypes, initiallynull.
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writerSpiNames
protected String[] writerSpiNames
An array of strings to be returned fromgetImageWriterSpiNames, initiallynull.
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Constructor Detail
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ImageReaderSpi
protected ImageReaderSpi()
Constructs a blankImageReaderSpi. It is up to the subclass to initialize instance variables and/or override method implementations in order to provide working versions of all methods.
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ImageReaderSpi
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)
Constructs anImageReaderSpiwith a given set of values.- Parameters:
vendorName- the vendor name, as a non-nullString.version- a version identifier, as a non-nullString.names- a non-nullarray ofStrings indicating the format names. At least one entry must be present.suffixes- an array ofStrings indicating the common file suffixes. If no suffixes are defined,nullshould be supplied. An array of length 0 will be normalized tonull.MIMETypes- an array ofStrings indicating the format's MIME types. If no MIME types are defined,nullshould be supplied. An array of length 0 will be normalized tonull.readerClassName- the fully-qualified name of the associatedImageReaderclass, as a non-null String.inputTypes- a non-nullarray ofClassobjects of length at least 1 indicating the legal input types.writerSpiNames- an arrayStrings naming the classes of all associatedImageWriters, ornull. An array of length 0 is normalized tonull.supportsStandardStreamMetadataFormat- abooleanthat indicates whether a stream metadata object can use trees described by the standard metadata format.nativeStreamMetadataFormatName- aString, ornull, to be returned fromgetNativeStreamMetadataFormatName.nativeStreamMetadataFormatClassName- aString, ornull, to be used to instantiate a metadata format object to be returned fromgetNativeStreamMetadataFormat.extraStreamMetadataFormatNames- an array ofStrings, ornull, to be returned fromgetExtraStreamMetadataFormatNames. An array of length 0 is normalized tonull.extraStreamMetadataFormatClassNames- an array ofStrings, ornull, to be used to instantiate a metadata format object to be returned fromgetStreamMetadataFormat. An array of length 0 is normalized tonull.supportsStandardImageMetadataFormat- abooleanthat indicates whether an image metadata object can use trees described by the standard metadata format.nativeImageMetadataFormatName- aString, ornull, to be returned fromgetNativeImageMetadataFormatName.nativeImageMetadataFormatClassName- aString, ornull, to be used to instantiate a metadata format object to be returned fromgetNativeImageMetadataFormat.extraImageMetadataFormatNames- an array ofStrings to be returned fromgetExtraImageMetadataFormatNames. An array of length 0 is normalized tonull.extraImageMetadataFormatClassNames- an array ofStrings, ornull, to be used to instantiate a metadata format object to be returned fromgetImageMetadataFormat. An array of length 0 is normalized tonull.- Throws:
IllegalArgumentException- ifvendorNameisnull.IllegalArgumentException- ifversionisnull.IllegalArgumentException- ifnamesisnullor has length 0.IllegalArgumentException- ifreaderClassNameisnull.IllegalArgumentException- ifinputTypesisnullor has length 0.
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Method Detail
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getInputTypes
public Class<?>[] getInputTypes()
Returns an array ofClassobjects indicating what types of objects may be used as arguments to the reader'ssetInputmethod.For most readers, which only accept input from an
ImageInputStream, a single-element array containingImageInputStream.classshould be returned.- Returns:
- a non-
nullarray ofClassobjects of length at least 1.
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canDecodeInput
public abstract boolean canDecodeInput(Object source) throws IOException
Returnstrueif the supplied source object appears to be of the format supported by this reader. Returningtruefrom 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 anImageInputStream, 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 anImageInputStream, amark/resetpair should be used to preserve the stream position.Formats such as "raw," which can potentially attempt to read nearly any stream, should return
falsein order to avoid being invoked in preference to a closer match.If
sourceis not an instance of one of the classes returned bygetInputTypes, the method should simply returnfalse.- Parameters:
source- the object (typically anImageInputStream) to be decoded.- Returns:
trueif it is likely that this stream can be decoded.- Throws:
IllegalArgumentException- ifsourceisnull.IOException- if an I/O error occurs while reading the stream.
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createReaderInstance
public ImageReader createReaderInstance() throws IOException
Returns an instance of theImageReaderimplementation associated with this service provider. The returned object will initially be in an initial state as if itsresetmethod had been called.The default implementation simply returns
createReaderInstance(null).- Returns:
- an
ImageReaderinstance. - Throws:
IOException- if an error occurs during loading, or initialization of the reader class, or during instantiation or initialization of the reader object.
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createReaderInstance
public abstract ImageReader createReaderInstance(Object extension) throws IOException
Returns an instance of theImageReaderimplementation associated with this service provider. The returned object will initially be in an initial state as if itsresetmethod had been called.An
Objectmay 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).- Parameters:
extension- a plug-in specific extension object, which may benull.- Returns:
- an
ImageReaderinstance. - Throws:
IOException- if the attempt to instantiate the reader fails.IllegalArgumentException- if theImageReader's constructor throws anIllegalArgumentExceptionto indicate that the extension object is unsuitable.
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isOwnReader
public boolean isOwnReader(ImageReader reader)
Returnstrueif theImageReaderobject passed in is an instance of theImageReaderassociated with this service provider.The default implementation compares the fully-qualified class name of the
readerargument with the class name passed into the constructor. This method may be overridden if more sophisticated checking is required.- Parameters:
reader- anImageReaderinstance.- Returns:
trueifreaderis recognized.- Throws:
IllegalArgumentException- ifreaderisnull.
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getImageWriterSpiNames
public String[] getImageWriterSpiNames()
Returns an array ofStrings containing the fully qualified names of all theImageWriterSpiclasses that can understand the internal metadata representation used by theImageReaderassociated with this service provider, ornullif there are no suchImageWriters specified. If a non-nullvalue 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
ImageWriterreturned byImageIO.getImageWriter(ImageReader).This mechanism may be used to obtain
ImageWritersthat will understand the internal structure of non-pixel meta-data (seeIIOTreeInfo) generated by anImageReader. By obtaining this data from theImageReaderand passing it on to one of theImageWritersobtained 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.- Returns:
- an array of
Strings of length at least 1 containing names ofImageWriterSpi, ornull. - See Also:
ImageIO.getImageWriter(ImageReader)
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