Package org.apache.xmlgraphics.image.loader

Interface ImageSessionContext

All Known Implementing Classes:

AbstractImageSessionContext, DefaultImageSessionContext

public interface ImageSessionContext

This interface is used to tell the cache which images are used by a session (in FOP that would be a rendering run). Images access within a session get a hard reference so they cannot be discarded. That could increase memory usage but helps with performance because the images don't get unloaded between layout and rendering which would mean that they have to be reloaded.

Method Summary

Modifier and Type	Method	Description
ImageContext	getParentContext()	Returns the session-independent context object which provides configuration information.
Source	getSource(String uri)	Returns a Source object for a URI.
float	getTargetResolution()	Returns the resolution (in dpi) of the target device used when painting images.
Source	needSource(String uri)	Returns a Source object for a URI.
Source	newSource(String uri)	Attempts to create a Source object from the given URI.
void	returnSource(String uri, Source src)	Returns a Source object to a pool.

Method Detail

getParentContext

ImageContext getParentContext()

Returns the session-independent context object which provides configuration information.

Returns:

the associated ImageContext instance

getTargetResolution

float getTargetResolution()

Returns the resolution (in dpi) of the target device used when painting images.

Returns:

the target resolution (in dpi)

newSource

Source newSource(String uri)

Attempts to create a Source object from the given URI. If possible this method returns an ImageSource instance which provides the best possible method to access the image.

Parameters:

uri - URI to access

Returns:

A Source object, or null if the URI cannot be resolved.

getSource

Source getSource(String uri)

Returns a Source object for a URI. This method is not guaranteed to return an instance. Implementations normally return already created Sources from a pool (normally populated through the returnSource(String, Source) method).

Parameters:

uri - the URI of the image

Returns:

the Source object to load the image from, or null

needSource

Source needSource(String uri)
           throws FileNotFoundException

Returns a Source object for a URI. This method is guaranteed to return a Source object. If the image cannot be found, a FileNotFoundException is thrown.

Parameters:

uri - the URI of the image

Returns:

the Source object to load the image from

Throws:

FileNotFoundException - if the image cannot be found

returnSource

void returnSource(String uri,
                  Source src)

Returns a Source object to a pool. This is provided in order to reuse a Source object between the preloading and the final loading of an image. Note that not all Source objects can be reused! Non-reusable Sources are discarded.

Parameters:

uri - the URI of the image

src - the Source object belonging to the URI