Class ImageReaderSpi
- java.lang.Object
-
- javax.imageio.spi.IIOServiceProvider
-
- javax.imageio.spi.ImageReaderWriterSpi
-
- javax.imageio.spi.ImageReaderSpi
- All Implemented Interfaces:
RegisterableService
public abstract class ImageReaderSpi extends ImageReaderWriterSpi
The service provider interface (SPI) for 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.
- See Also:
-
IIORegistry
,ImageReader
Field Summary
Modifier and Type | Field | Description |
---|---|---|
protected Class<?>[] | inputTypes | An array of |
static Class<?>[] | STANDARD_INPUT_TYPE | Deprecated. Instead of using this field, directly create the equivalent array { ImageInputStream.class } . |
protected String[] | writerSpiNames | An array of strings to be returned from |
Fields declared in class javax.imageio.spi.ImageReaderWriterSpi
extraImageMetadataFormatClassNames, extraImageMetadataFormatNames, extraStreamMetadataFormatClassNames, extraStreamMetadataFormatNames, MIMETypes, names, nativeImageMetadataFormatClassName, nativeImageMetadataFormatName, nativeStreamMetadataFormatClassName, nativeStreamMetadataFormatName, pluginClassName, suffixes, supportsStandardImageMetadataFormat, supportsStandardStreamMetadataFormat
Fields declared in class javax.imageio.spi.IIOServiceProvider
vendorName, version
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | ImageReaderSpi() | Constructs a blank |
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 an |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
abstract boolean | canDecodeInput(Object source) | Returns |
ImageReader | createReaderInstance() | Returns an instance of the |
abstract ImageReader | createReaderInstance(Object extension) | Returns an instance of the |
String[] | getImageWriterSpiNames() | Returns an array of |
Class<?>[] | getInputTypes() | Returns an array of |
boolean | isOwnReader(ImageReader reader) | Returns |
Methods declared in class javax.imageio.spi.ImageReaderWriterSpi
getExtraImageMetadataFormatNames, getExtraStreamMetadataFormatNames, getFileSuffixes, getFormatNames, getImageMetadataFormat, getMIMETypes, getNativeImageMetadataFormatName, getNativeStreamMetadataFormatName, getPluginClassName, getStreamMetadataFormat, isStandardImageMetadataFormatSupported, isStandardStreamMetadataFormatSupported
Methods declared in class javax.imageio.spi.IIOServiceProvider
getDescription, getVendorName, getVersion, onDeregistration, onRegistration
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Field Detail
STANDARD_INPUT_TYPE
@Deprecated public static final Class<?>[] STANDARD_INPUT_TYPE
{ ImageInputStream.class }
.A single-element array, initially containing ImageInputStream.class
, to be returned from getInputTypes
.
inputTypes
protected Class<?>[] inputTypes
An array of Class
objects to be returned from getInputTypes
, initially null
.
writerSpiNames
protected String[] writerSpiNames
An array of strings to be returned from getImageWriterSpiNames
, initially null
.
Constructor Detail
ImageReaderSpi
protected ImageReaderSpi()
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.
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 an ImageReaderSpi
with a given set of values.
- Parameters:
-
vendorName
- the vendor name, as a non-null
String
. -
version
- a version identifier, as a non-null
String
. -
names
- a non-null
array ofString
s indicating the format names. At least one entry must be present. -
suffixes
- an array ofString
s indicating the common file suffixes. If no suffixes are defined,null
should be supplied. An array of length 0 will be normalized tonull
. -
MIMETypes
- an array ofString
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 tonull
. -
readerClassName
- the fully-qualified name of the associatedImageReader
class, as a non-null String
. -
inputTypes
- a non-null
array ofClass
objects of length at least 1 indicating the legal input types. -
writerSpiNames
- an arrayString
s naming the classes of all associatedImageWriter
s, ornull
. An array of length 0 is normalized tonull
. -
supportsStandardStreamMetadataFormat
- aboolean
that 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 ofString
s, ornull
, to be returned fromgetExtraStreamMetadataFormatNames
. An array of length 0 is normalized tonull
. -
extraStreamMetadataFormatClassNames
- an array ofString
s, ornull
, to be used to instantiate a metadata format object to be returned fromgetStreamMetadataFormat
. An array of length 0 is normalized tonull
. -
supportsStandardImageMetadataFormat
- aboolean
that 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 ofString
s to be returned fromgetExtraImageMetadataFormatNames
. An array of length 0 is normalized tonull
. -
extraImageMetadataFormatClassNames
- an array ofString
s, ornull
, to be used to instantiate a metadata format object to be returned fromgetImageMetadataFormat
. An array of length 0 is normalized tonull
. - Throws:
-
IllegalArgumentException
- ifvendorName
isnull
. -
IllegalArgumentException
- ifversion
isnull
. -
IllegalArgumentException
- ifnames
isnull
or has length 0. -
IllegalArgumentException
- ifreaderClassName
isnull
. -
IllegalArgumentException
- ifinputTypes
isnull
or has length 0.
Method Detail
getInputTypes
public Class<?>[] getInputTypes()
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 ofClass
objects of length at least 1.
canDecodeInput
public abstract boolean canDecodeInput(Object source) throws IOException
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 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
.
- Parameters:
-
source
- the object (typically anImageInputStream
) to be decoded. - Returns:
-
true
if it is likely that this stream can be decoded. - Throws:
-
IllegalArgumentException
- ifsource
isnull
. -
IOException
- if an I/O error occurs while reading the stream.
createReaderInstance
public ImageReader createReaderInstance() 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)
.
- Returns:
- an
ImageReader
instance. - Throws:
-
IOException
- if an error occurs during loading, or initialization of the reader class, or during instantiation or initialization of the reader object.
createReaderInstance
public abstract ImageReader createReaderInstance(Object extension) 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.
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)
.
- Parameters:
-
extension
- a plug-in specific extension object, which may benull
. - Returns:
- an
ImageReader
instance. - Throws:
-
IOException
- if the attempt to instantiate the reader fails. -
IllegalArgumentException
- if theImageReader
's constructor throws anIllegalArgumentException
to indicate that the extension object is unsuitable.
isOwnReader
public boolean isOwnReader(ImageReader reader)
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.
- Parameters:
-
reader
- anImageReader
instance. - Returns:
-
true
ifreader
is recognized. - Throws:
-
IllegalArgumentException
- ifreader
isnull
.
getImageWriterSpiNames
public 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. 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.
- Returns:
- an array of
String
s of length at least 1 containing names ofImageWriterSpi
, ornull
. - See Also:
ImageIO.getImageWriter(ImageReader)