Class ImageWriterSpi
- java.lang.Object
-
- javax.imageio.spi.IIOServiceProvider
-
- javax.imageio.spi.ImageReaderWriterSpi
-
- javax.imageio.spi.ImageWriterSpi
- All Implemented Interfaces:
RegisterableService
public abstract class ImageWriterSpi extends ImageReaderWriterSpi
The service provider interface (SPI) for ImageWriter
s. For more information on service provider classes, see the class comment for the IIORegistry
class.
Each ImageWriterSpi
provides several types of information about the ImageWriter
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-writable 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 getMIMEType
methods. These methods may be used to identify candidate ImageWriter
s for writing a particular file or stream based on manual format selection, file naming, or MIME associations.
A more reliable way to determine which ImageWriter
s are likely to be able to parse a particular data stream is provided by the canEncodeImage
method. This methods allows the service provider to inspect the actual image contents.
Finally, an instance of the ImageWriter
class associated with this service provider may be obtained by calling the createWriterInstance
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
,ImageTypeSpecifier
,ImageWriter
Field Summary
Modifier and Type | Field | Description |
---|---|---|
protected Class<?>[] | outputTypes | An array of |
protected String[] | readerSpiNames | An array of strings to be returned from |
static Class<?>[] | STANDARD_OUTPUT_TYPE | Deprecated. Instead of using this field, directly create the equivalent array { ImageOutputStream.class } . |
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 | ImageWriterSpi() | Constructs a blank |
ImageWriterSpi(String vendorName,
String version,
String[] names,
String[] suffixes,
String[] MIMETypes,
String writerClassName,
Class<?>[] outputTypes,
String[] readerSpiNames,
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 |
---|---|---|
boolean | canEncodeImage(RenderedImage im) | Returns |
abstract boolean | canEncodeImage(ImageTypeSpecifier type) | Returns |
ImageWriter | createWriterInstance() | Returns an instance of the |
abstract ImageWriter | createWriterInstance(Object extension) | Returns an instance of the |
String[] | getImageReaderSpiNames() | Returns an array of |
Class<?>[] | getOutputTypes() | Returns an array of |
boolean | isFormatLossless() | Returns |
boolean | isOwnWriter(ImageWriter writer) | 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_OUTPUT_TYPE
@Deprecated public static final Class<?>[] STANDARD_OUTPUT_TYPE
{ ImageOutputStream.class }
.A single-element array, initially containing ImageOutputStream.class
, to be returned from getOutputTypes
.
outputTypes
protected Class<?>[] outputTypes
An array of Class
objects to be returned from getOutputTypes
, initially null
.
readerSpiNames
protected String[] readerSpiNames
An array of strings to be returned from getImageReaderSpiNames
, initially null
.
Constructor Detail
ImageWriterSpi
protected ImageWriterSpi()
Constructs a blank ImageWriterSpi
. It is up to the subclass to initialize instance variables and/or override method implementations in order to provide working versions of all methods.
ImageWriterSpi
public ImageWriterSpi(String vendorName, String version, String[] names, String[] suffixes, String[] MIMETypes, String writerClassName, Class<?>[] outputTypes, String[] readerSpiNames, boolean supportsStandardStreamMetadataFormat, String nativeStreamMetadataFormatName, String nativeStreamMetadataFormatClassName, String[] extraStreamMetadataFormatNames, String[] extraStreamMetadataFormatClassNames, boolean supportsStandardImageMetadataFormat, String nativeImageMetadataFormatName, String nativeImageMetadataFormatClassName, String[] extraImageMetadataFormatNames, String[] extraImageMetadataFormatClassNames)
Constructs an ImageWriterSpi
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 suffixes are defined,null
should be supplied. An array of length 0 will be normalized tonull
. -
writerClassName
- the fully-qualified name of the associatedImageWriterSpi
class, as a non-null String
. -
outputTypes
- an array ofClass
objects of length at least 1 indicating the legal output types. -
readerSpiNames
- an arrayString
s of length at least 1 naming the classes of all associatedImageReader
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
- ifwriterClassName
isnull
. -
IllegalArgumentException
- ifoutputTypes
isnull
or has length 0.
Method Detail
isFormatLossless
public boolean isFormatLossless()
Returns true
if the format that this writer outputs preserves pixel data bit-accurately. The default implementation returns true
.
- Returns:
-
true
if the format preserves full pixel accuracy.
getOutputTypes
public Class<?>[] getOutputTypes()
Returns an array of Class
objects indicating what types of objects may be used as arguments to the writer's setOutput
method.
For most writers, which only output to an ImageOutputStream
, a single-element array containing ImageOutputStream.class
should be returned.
- Returns:
- a non-
null
array ofClass
objects of length at least 1.
canEncodeImage
public abstract boolean canEncodeImage(ImageTypeSpecifier type)
Returns true
if the ImageWriter
implementation associated with this service provider is able to encode an image with the given layout. The layout (i.e., the image's SampleModel
and ColorModel
) is described by an ImageTypeSpecifier
object.
A return value of true
is not an absolute guarantee of successful encoding; the encoding process may still produce errors due to factors such as I/O errors, inconsistent or malformed data structures, etc. The intent is that a reasonable inspection of the basic structure of the image be performed in order to determine if it is within the scope of the encoding format. For example, a service provider for a format that can only encode greyscale would return false
if handed an RGB BufferedImage
. Similarly, a service provider for a format that can encode 8-bit RGB imagery might refuse to encode an image with an associated alpha channel.
Different ImageWriter
s, and thus service providers, may choose to be more or less strict. For example, they might accept an image with premultiplied alpha even though it will have to be divided out of each pixel, at some loss of precision, in order to be stored.
- Parameters:
-
type
- anImageTypeSpecifier
specifying the layout of the image to be written. - Returns:
-
true
if this writer is likely to be able to encode images with the given layout. - Throws:
-
IllegalArgumentException
- iftype
isnull
.
canEncodeImage
public boolean canEncodeImage(RenderedImage im)
Returns true
if the ImageWriter
implementation associated with this service provider is able to encode the given RenderedImage
instance. Note that this includes instances of java.awt.image.BufferedImage
.
See the discussion for canEncodeImage(ImageTypeSpecifier)
for information on the semantics of this method.
- Parameters:
-
im
- an instance ofRenderedImage
to be encoded. - Returns:
-
true
if this writer is likely to be able to encode this image. - Throws:
-
IllegalArgumentException
- ifim
isnull
.
createWriterInstance
public ImageWriter createWriterInstance() throws IOException
Returns an instance of the ImageWriter
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 createWriterInstance(null)
.
- Returns:
- an
ImageWriter
instance. - Throws:
-
IOException
- if an error occurs during loading, or initialization of the writer class, or during instantiation or initialization of the writer object.
createWriterInstance
public abstract ImageWriter createWriterInstance(Object extension) throws IOException
Returns an instance of the ImageWriter
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 MyImageWriter(this)
.
- Parameters:
-
extension
- a plug-in specific extension object, which may benull
. - Returns:
- an
ImageWriter
instance. - Throws:
-
IOException
- if the attempt to instantiate the writer fails. -
IllegalArgumentException
- if theImageWriter
's constructor throws anIllegalArgumentException
to indicate that the extension object is unsuitable.
isOwnWriter
public boolean isOwnWriter(ImageWriter writer)
Returns true
if the ImageWriter
object passed in is an instance of the ImageWriter
associated with this service provider.
- Parameters:
-
writer
- anImageWriter
instance. - Returns:
-
true
ifwriter
is recognized - Throws:
-
IllegalArgumentException
- ifwriter
isnull
.
getImageReaderSpiNames
public String[] getImageReaderSpiNames()
Returns an array of String
s containing all the fully qualified names of all the ImageReaderSpi
classes that can understand the internal metadata representation used by the ImageWriter
associated with this service provider, or null
if there are no such ImageReaders
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" reader, as it will be used to instantiate the ImageReader
returned by ImageIO.getImageReader(ImageWriter)
.
This mechanism may be used to obtain ImageReaders
that will generated non-pixel meta-data (see IIOExtraDataInfo
) in a structure understood by an ImageWriter
. By reading the image and obtaining this data from one of the ImageReaders
obtained with this method and passing it on to the ImageWriter
, a client program can read an image, modify it in some way, and write it back out 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 ofImageReaderSpi
s, ornull
. - See Also:
-
ImageIO.getImageReader(ImageWriter)
,ImageReaderSpi.getImageWriterSpiNames()