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package java.awt;
import java.awt.image.ColorModel;
The Composite
interface, along with CompositeContext
, defines the methods to compose a draw primitive with the underlying graphics area. After the Composite
is set in the 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
AWTPermission
. The permission check will occur when such a custom object is passed to the setComposite
method
of a Graphics2D
retrieved from a Component
.
See Also:
/**
* The <code>Composite</code> interface, along with
* {@link CompositeContext}, defines the methods to compose a draw
* primitive with the underlying graphics area.
* After the <code>Composite</code> 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.
* <code>CompositeContext</code> is an environment used by the
* compositing operation, which is created by the <code>Graphics2D</code>
* prior to the start of the operation. <code>CompositeContext</code>
* contains private information and resources needed for a compositing
* operation. When the <code>CompositeContext</code> is no longer needed,
* the <code>Graphics2D</code> object disposes of it in order to reclaim
* resources allocated for the operation.
* <p>
* Instances of classes implementing <code>Composite</code> must be
* immutable because the <code>Graphics2D</code> does not clone
* these objects when they are set as an attribute with the
* <code>setComposite</code> method or when the <code>Graphics2D</code>
* object is cloned. This is to avoid undefined rendering behavior of
* <code>Graphics2D</code>, resulting from the modification of
* the <code>Composite</code> object after it has been set in the
* <code>Graphics2D</code> context.
* <p>
* 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 <code>readDisplayPixels</code>
* {@link AWTPermission}. The permission check will occur when such
* a custom object is passed to the <code>setComposite</code> method
* of a <code>Graphics2D</code> retrieved from a {@link Component}.
* @see AlphaComposite
* @see CompositeContext
* @see Graphics2D#setComposite
*/
public interface Composite {
Creates a context containing state that is used to perform
the compositing operation. In a multi-threaded environment,
several contexts can exist simultaneously for a single
Composite
object.
Params: - srcColorModel – the
ColorModel
of the source - dstColorModel – the
ColorModel
of the destination - hints – the hint that the context object uses to choose between
rendering alternatives
Returns: the CompositeContext
object used to perform the
compositing operation.
/**
* Creates a context containing state that is used to perform
* the compositing operation. In a multi-threaded environment,
* several contexts can exist simultaneously for a single
* <code>Composite</code> object.
* @param srcColorModel the {@link ColorModel} of the source
* @param dstColorModel the <code>ColorModel</code> of the destination
* @param hints the hint that the context object uses to choose between
* rendering alternatives
* @return the <code>CompositeContext</code> object used to perform the
* compositing operation.
*/
public CompositeContext createContext(ColorModel srcColorModel,
ColorModel dstColorModel,
RenderingHints hints);
}