ImageWriterSpi (Java SE 25 & JDK 25)
Description: declaration: module: java.desktop, package: javax.imageio.spi, class: ImageWriterSpi
Keywords: javax.imageio.spi.ImageWriterSpi class

# 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

  Fields
  Modifier and Type
  Field
  Description
  `protected Class<?>[]`
  `outputTypes`
  An array of `Class` objects to be returned from `getOutputTypes`, initially `null`.
  `protected String[]`
  `readerSpiNames`
  An array of strings to be returned from `getImageReaderSpiNames`, initially `null`.
  `static final Class<?>[]`
  `STANDARD_OUTPUT_TYPE`
  Deprecated.
  Instead of using this field, directly create the equivalent array `{ ImageOutputStream.class }`.

  ### Fields declared in class ImageReaderWriterSpi

  `extraImageMetadataFormatClassNames, extraImageMetadataFormatNames, extraStreamMetadataFormatClassNames, extraStreamMetadataFormatNames, MIMETypes, names, nativeImageMetadataFormatClassName, nativeImageMetadataFormatName, nativeStreamMetadataFormatClassName, nativeStreamMetadataFormatName, pluginClassName, suffixes, supportsStandardImageMetadataFormat, supportsStandardStreamMetadataFormat`

  ### Fields declared in class IIOServiceProvider

  `vendorName, version`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `ImageWriterSpi()`
  Constructs a blank `ImageWriterSpi`.
  ``
  `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.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `canEncodeImage(RenderedImage im)`
  Returns `true` if the `ImageWriter` implementation associated with this service provider is able to encode the given `RenderedImage` instance.
  `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.
  `ImageWriter`
  `createWriterInstance()`
  Returns an instance of the `ImageWriter` implementation associated with this service provider.
  `abstract ImageWriter`
  `createWriterInstance(Object extension)`
  Returns an instance of the `ImageWriter` implementation associated with this service provider.
  `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.
  `Class<?>[]`
  `getOutputTypes()`
  Returns an array of `Class` objects indicating what types of objects may be used as arguments to the writer's `setOutput` method.
  `boolean`
  `isFormatLossless()`
  Returns `true` if the format that this writer outputs preserves pixel data bit-accurately.
  `boolean`
  `isOwnWriter(ImageWriter writer)`
  Returns `true` if the `ImageWriter` object passed in is an instance of the `ImageWriter` associated with this service provider.

  ### Methods declared in class ImageReaderWriterSpi

  `getExtraImageMetadataFormatNames, getExtraStreamMetadataFormatNames, getFileSuffixes, getFormatNames, getImageMetadataFormat, getMIMETypes, getNativeImageMetadataFormatName, getNativeStreamMetadataFormatName, getPluginClassName, getStreamMetadataFormat, isStandardImageMetadataFormatSupported, isStandardStreamMetadataFormatSupported`

  ### Methods declared in class IIOServiceProvider

  `getDescription, getVendorName, getVersion, onDeregistration, onRegistration`

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### STANDARD_OUTPUT_TYPE

    @Deprecated public static final Class<?>[] STANDARD_OUTPUT_TYPE
    Deprecated.
    Instead of using this field, directly create the equivalent array `{ 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 Details

  - ### 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 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 suffixes are defined, `null` should be supplied. An array of length 0 will be normalized to `null`.
      `writerClassName` - the fully-qualified name of the associated `ImageWriterSpi` class, as a non-`null String`.
      `outputTypes` - an array of `Class` objects of length at least 1 indicating the legal output types.
      `readerSpiNames` - an array `String`s of length at least 1 naming the classes of all associated `ImageReader`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`.
    Throws:
      `IllegalArgumentException` - if `vendorName` is `null`.
      `IllegalArgumentException` - if `version` is `null`.
      `IllegalArgumentException` - if `names` is `null` or has length 0.
      `IllegalArgumentException` - if `writerClassName` is `null`.
      `IllegalArgumentException` - if `outputTypes` is `null` or has length 0.

- ## Method Details

  - ### 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 of `Class` 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` - an `ImageTypeSpecifier` 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` - if `type` is `null`.

  - ### 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 of `RenderedImage` to be encoded.
    Returns:
      `true` if this writer is likely to be able to encode this image.
    Throws:
      `IllegalArgumentException` - if `im` is `null`.

  - ### 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 be `null`.
    Returns:
      an `ImageWriter` instance.
    Throws:
      `IOException` - if the attempt to instantiate the writer fails.
      `IllegalArgumentException` - if the `ImageWriter`'s constructor throws an `IllegalArgumentException` 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` - an `ImageWriter` instance.
    Returns:
      `true` if `writer` is recognized
    Throws:
      `IllegalArgumentException` - if `writer` is `null`.

  - ### 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 of `ImageReaderSpi`s, or `null`.
    See Also:
      - `ImageIO.getImageReader(ImageWriter)`
      - `ImageReaderSpi.getImageWriterSpiNames()`