The Composite interface, along with
{@link CompositeContext}, defines the methods to compose a draw
primitive with the underlying graphics area.
After the Composite is set in the
{@link Graphics2D} context, it combines a shape, text, or an image
being rendered with the colors that have already been rendered
according to pre-defined rules. The classes
implementing this interface provide the rules and a method to create
the context for a particular operation.
CompositeContext is an environment used by the
compositing operation, which is created by the Graphics2D
prior to the start of the operation. CompositeContext
contains private information and resources needed for a compositing
operation. When the CompositeContext is no longer needed,
the Graphics2D object disposes of it in order to reclaim
resources allocated for the operation.
Instances of classes implementing Composite must be
immutable because the Graphics2D does not clone
these objects when they are set as an attribute with the
setComposite method or when the Graphics2D
object is cloned. This is to avoid undefined rendering behavior of
Graphics2D, resulting from the modification of
the Composite object after it has been set in the
Graphics2D context.
Since this interface must expose the contents of pixels on the
target device or image to potentially arbitrary code, the use of
custom objects which implement this interface when rendering directly
to a screen device is governed by the readDisplayPixels
{@link AWTPermission}. The permission check will occur when such
a custom object is passed to the setComposite method
of a Graphics2D retrieved from a {@link Component}. |
