Composite


1   /*
2    * @(#)Composite.java   1.23 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.awt;
9   
10  import java.awt.image.ColorModel  ;
11  
12  /**
13   * The <code>Composite</code> interface, along with 
14   * {@link CompositeContext}, defines the methods to compose a draw
15   * primitive with the underlying graphics area.
16   * After the <code>Composite</code> is set in the 
17   * {@link Graphics2D} context, it combines a shape, text, or an image
18   * being rendered with the colors that have already been rendered
19   * according to pre-defined rules. The classes
20   * implementing this interface provide the rules and a method to create
21   * the context for a particular operation.
22   * <code>CompositeContext</code> is an environment used by the 
23   * compositing operation, which is created by the <code>Graphics2D</code>
24   * prior to the start of the operation.  <code>CompositeContext</code>
25   * contains private information and resources needed for a compositing 
26   * operation.  When the <code>CompositeContext</code> is no longer needed,
27   * the <code>Graphics2D</code> object disposes of it in order to reclaim 
28   * resources allocated for the operation.
29   * <p>
30   * Instances of classes implementing <code>Composite</code> must be 
31   * immutable because the <code>Graphics2D</code> does not clone
32   * these objects when they are set as an attribute with the 
33   * <code>setComposite</code> method or when the <code>Graphics2D</code>
34   * object is cloned.  This is to avoid undefined rendering behavior of 
35   * <code>Graphics2D</code>, resulting from the modification of 
36   * the <code>Composite</code> object after it has been set in the 
37   * <code>Graphics2D</code> context.
38   * <p>
39   * Since this interface must expose the contents of pixels on the
40   * target device or image to potentially arbitrary code, the use of
41   * custom objects which implement this interface when rendering directly
42   * to a screen device is governed by the <code>readDisplayPixels</code>
43   * {@link AWTPermission}.  The permission check will occur when such
44   * a custom object is passed to the <code>setComposite</code> method
45   * of a <code>Graphics2D</code> retrieved from a {@link Component}.
46   * @see AlphaComposite
47   * @see CompositeContext
48   * @see Graphics2D#setComposite
49   * @version 10 Feb 1997
50   */
51  public interface Composite {
52  
53      /**
54       * Creates a context containing state that is used to perform
55       * the compositing operation.  In a multi-threaded environment,
56       * several contexts can exist simultaneously for a single
57       * <code>Composite</code> object.
58       * @param srcColorModel  the {@link ColorModel} of the source
59       * @param dstColorModel  the <code>ColorModel</code> of the destination
60       * @param hints the hint that the context object uses to choose between
61       * rendering alternatives
62       * @return the <code>CompositeContext</code> object used to perform the
63       * compositing operation.
64       */
65      public CompositeContext   createContext(ColorModel   srcColorModel,
66                        ColorModel   dstColorModel,
67                                            RenderingHints   hints);
68  
69  }
70
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