javax.imageio.metadata
class IIOMetadata

java.lang.Object javax.imageio.metadata.IIOMetadata

Most common way to construct:

ImageReader reader = …;

IIOMetadata meta = reader.getImageMetadata(0);

Based on 45 examples

public abstract class IIOMetadata
extends Object

An abstract class to be extended by objects that represent metadata (non-image data) associated with images and streams. Plug-ins represent metadata using opaque, plug-in specific objects. These objects, however, provide the ability to access their internal information as a tree of IIOMetadataNode objects that support the XML DOM interfaces as well as additional interfaces for storing non-textual data and retrieving information about legal data values. The format of such trees is plug-in dependent, but plug-ins may choose to support a plug-in neutral format described below. A single plug-in may support multiple metadata formats, whose names maybe determined by calling getMetadataFormatNames. The plug-in may also support a single special format, referred to as the "native" format, which is designed to encode its metadata losslessly. This format will typically be designed specifically to work with a specific file format, so that images may be loaded and saved in the same format with no loss of metadata, but may be less useful for transfering metadata between an ImageReader and an ImageWriter for different image formats. To convert between two native formats as losslessly as the image file formats will allow, an ImageTranscoder object must be used.

controller

protected IIOMetadataController controller

The IIOMetadataController that will be used to provide settings for this IIOMetadata object when the activateController method is called. This value overrides any default controller, even when null.

defaultController

protected IIOMetadataController defaultController

An IIOMetadataController that is suggested for use as the controller for this IIOMetadata object. It may be retrieved via getDefaultController. To install the default controller, call setController(getDefaultController()). This instance variable should be set by subclasses that choose to provide their own default controller, usually a GUI, for setting parameters.

extraMetadataFormatClassNames

protected String[] extraMetadataFormatClassNames

An array of names of classes implementing IIOMetadataFormat and representing the metadata formats, other than the standard and native formats, that are supported by this plug-in, initialized to null and set via the constructor.

extraMetadataFormatNames

protected String[] extraMetadataFormatNames

An array of names of formats, other than the standard and native formats, that are supported by this plug-in, initialized to null and set via the constructor.

nativeMetadataFormatClassName

protected String nativeMetadataFormatClassName

The name of the class implementing IIOMetadataFormat and representing the native metadata format, initialized to null and set via the constructor.

nativeMetadataFormatName

protected String nativeMetadataFormatName

The name of the native metadata format for this object, initialized to null and set via the constructor.

standardFormatSupported

protected boolean standardFormatSupported

A boolean indicating whether the concrete subclass supports the standard metadata format, set via the constructor.

IIOMetadata

protected IIOMetadata()

Constructs an empty IIOMetadata object. The subclass is responsible for suppying values for all protected instance variables that will allow any non-overridden default implemtations of methods to satisfy their contracts. For example, extraMetadataFormatNames should not have length 0.

IIOMetadata

protected IIOMetadata(boolean standardMetadataFormatSupported,
                      String nativeMetadataFormatName,
                      String nativeMetadataFormatClassName,
                      String[] extraMetadataFormatNames,
                      String[] extraMetadataFormatClassNames)

Constructs an IIOMetadata object with the given format names and format class names, as well as a boolean indicating whether the standard format is supported.

This constructor does not attempt to check the class names for validity. Invalid class names may cause exceptions in subsequent calls to getMetadataFormat.

Parameters:

standardMetadataFormatSupported - true if this object can return or accept a DOM tree using the standard metadata format.

nativeMetadataFormatName - the name of the native metadata format, as a String, or null if there is no native format.

nativeMetadataFormatClassName - the name of the class of the native metadata format, or null if there is no native format.

extraMetadataFormatNames - an array of Strings indicating additional formats supported by this object, or null if there are none.

extraMetadataFormatClassNames - an array of Strings indicating the class names of any additional formats supported by this object, or null if there are none.

activateController

public boolean activateController()

Activates the installed IIOMetadataController for this IIOMetadata object and returns the resulting value. When this method returns true, all values for this IIOMetadata object will be ready for the next write operation. If false is returned, no settings in this object will have been disturbed (i.e., the user canceled the operation).

Ordinarily, the controller will be a GUI providing a user interface for a subclass of IIOMetadata for a particular plug-in. Controllers need not be GUIs, however.

The default implementation calls getController and the calls activate on the returned object if hasController returns true.

Returns:

true if the controller completed normally.

getAsTree

public abstract Node getAsTree(String formatName)

Returns an XML DOM Node object that represents the root of a tree of metadata contained within this object according to the conventions defined by a given metadata format.

The names of the available metadata formats may be queried using the getMetadataFormatNames method.

Parameters:

formatName - the desired metadata format.

Returns:

an XML DOM Node object forming the root of a tree.

getController

public IIOMetadataController getController()

Returns whatever IIOMetadataController is currently installed. This could be the default if there is one, null, or the argument of the most recent call to setController.

The default implementation returns the value of the controller instance variable.

Returns:

the currently installed IIOMetadataController, or null.

getDefaultController

public IIOMetadataController getDefaultController()

Returns the default IIOMetadataController, if there is one, regardless of the currently installed controller. If there is no default controller, returns null.

The default implementation returns the value of the defaultController instance variable.

Returns:

the default IIOMetadataController, or null.

getExtraMetadataFormatNames

public String[] getExtraMetadataFormatNames()

Returns an array of Strings containing the names of additional metadata formats, other than the native and standard formats, recognized by this plug-in's getAsTree, setFromTree, and mergeTree methods. If there are no such additional formats, null is returned.

The default implementation returns a clone of the extraMetadataFormatNames instance variable.

Returns:

an array of Strings with length at least 1, or null.

getMetadataFormat

public IIOMetadataFormat getMetadataFormat(String formatName)

Returns an IIOMetadataFormat object describing the given metadata format, or null if no description is available. The supplied name must be one of those returned by getMetadataFormatNames (i.e., either the native format name, the standard format name, or one of those returned by getExtraMetadataFormatNames).

The default implementation checks the name against the global standard metadata format name, and returns that format if it is supported. Otherwise, it checks against the native format names followed by any additional format names. If a match is found, it retrieves the name of the IIOMetadataFormat class from nativeMetadataFormatClassName or extraMetadataFormatClassNames as appropriate, and constructs an instance of that class using its getInstance method.

Parameters:

formatName - the desired metadata format.

Returns:

an IIOMetadataFormat object.

getMetadataFormatNames

public String[] getMetadataFormatNames()

Returns an array of Strings containing the names of all metadata formats, including the native and standard formats, recognized by this plug-in's getAsTree, setFromTree, and mergeTree methods. If there are no such formats, null is returned.

The default implementation calls getNativeMetadataFormatName, isStandardMetadataFormatSupported, and getExtraMetadataFormatNames and returns the combined results.

Returns:

an array of Strings.

getNativeMetadataFormatName

public String getNativeMetadataFormatName()

Returns the name of the "native" metadata format for this plug-in, which typically allows for lossless encoding and transmission of the metadata stored in the format handled by this plug-in. If no such format is supported, nullwill be returned.

The structure and contents of the "native" metadata format are defined by the plug-in that created this IIOMetadata object. Plug-ins for simple formats will usually create a dummy node for the root, and then a series of child nodes representing individual tags, chunks, or keyword/value pairs. A plug-in may choose whether or not to document its native format.

The default implementation returns the value of the nativeMetadataFormatName instance variable.

Returns:

the name of the native format, or null.

getStandardChromaNode

protected IIOMetadataNode getStandardChromaNode()

Returns an IIOMetadataNode representing the chroma information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardCompressionNode

protected IIOMetadataNode getStandardCompressionNode()

Returns an IIOMetadataNode representing the compression information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardDataNode

protected IIOMetadataNode getStandardDataNode()

Returns an IIOMetadataNode representing the data format information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardDimensionNode

protected IIOMetadataNode getStandardDimensionNode()

Returns an IIOMetadataNode representing the dimension information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardDocumentNode

protected IIOMetadataNode getStandardDocumentNode()

Returns an IIOMetadataNode representing the document information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardTextNode

protected IIOMetadataNode getStandardTextNode()

Returns an IIOMetadataNode representing the textual information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardTileNode

protected IIOMetadataNode getStandardTileNode()

Returns an IIOMetadataNode representing the tiling information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardTransparencyNode

protected IIOMetadataNode getStandardTransparencyNode()

Returns an IIOMetadataNode representing the transparency information of the standard javax_imageio_1.0 metadata format, or null if no such information is available. This method is intended to be called by the utility routine getStandardTree.

The default implementation returns null.

Subclasses should override this method to produce an appropriate subtree if they wish to support the standard metadata format.

Returns:

an IIOMetadataNode, or null.

getStandardTree

protected final IIOMetadataNode getStandardTree()

A utility method to return a tree of IIOMetadataNodes representing the metadata contained within this object according to the conventions of the standard javax_imageio_1.0 metadata format.

This method calls the various getStandard*Node methods to supply each of the subtrees rooted at the children of the root node. If any of those methods returns null, the corresponding subtree will be omitted. If all of them return null, a tree consisting of a single root node will be returned.

Returns:

an IIOMetadataNode representing the root of a metadata tree in the javax_imageio_1.0 format.

hasController

public boolean hasController()

Returns true if there is a controller installed for this IIOMetadata object.

The default implementation returns true if the getController method returns a non-null value.

Returns:

true if a controller is installed.

isReadOnly

public abstract boolean isReadOnly()

Returns true if this object does not support the mergeTree, setFromTree, and reset methods.

Returns:

true if this IIOMetadata object cannot be modified.

isStandardMetadataFormatSupported

public boolean isStandardMetadataFormatSupported()

Returns true if the standard metadata format is supported by getMetadataFormat, getAsTree, setFromTree, and mergeTree.

The default implementation returns the value of the standardFormatSupported instance variable.

Returns:

true if the standard metadata format is supported.

mergeTree

public abstract void mergeTree(String formatName,
                               Node root)
                        throws IIOInvalidTreeException

Alters the internal state of this IIOMetadata object from a tree of XML DOM Nodes whose syntax is defined by the given metadata format. The previous state is altered only as necessary to accomodate the nodes that are present in the given tree. If the tree structure or contents are invalid, an IIOInvalidTreeException will be thrown.

As the semantics of how a tree or subtree may be merged with another tree are completely format-specific, plug-in authors may implement this method in whatever manner is most appropriate for the format, including simply replacing all existing state with the contents of the given tree.

Parameters:

formatName - the desired metadata format.

root - an XML DOM Node object forming the root of a tree.

Throws:

IIOInvalidTreeException - if the tree cannot be parsed successfully using the rules of the given format.

reset

public abstract void reset()

Resets all the data stored in this object to default values, usually to the state this object was in immediately after construction, though the precise semantics are plug-in specific. Note that there are many possible default values, depending on how the object was created.

setController

public void setController(IIOMetadataController controller)

Sets the IIOMetadataController to be used to provide settings for this IIOMetadata object when the activateController method is called, overriding any default controller. If the argument is null, no controller will be used, including any default. To restore the default, use setController(getDefaultController()).

The default implementation sets the controller instance variable to the supplied value.

Parameters:

controller - An appropriate IIOMetadataController, or null.

setFromTree

public void setFromTree(String formatName,
                        Node root)
                 throws IIOInvalidTreeException

Sets the internal state of this IIOMetadata object from a tree of XML DOM Nodes whose syntax is defined by the given metadata format. The previous state is discarded. If the tree's structure or contents are invalid, an IIOInvalidTreeException will be thrown.

The default implementation calls reset followed by mergeTree(formatName, root).

Parameters:

formatName - the desired metadata format.

root - an XML DOM Node object forming the root of a tree.

Throws:

IIOInvalidTreeException - if the tree cannot be parsed successfully using the rules of the given format.