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1   /*
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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5    * This code is free software; you can redistribute it and/or modify it
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7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
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19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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25  
26  package java.awt;
27  
28  import java.awt.image.ColorModel;
29  
30  /**
31   * The <code>Composite</code> interface, along with
32   * {@link CompositeContext}, defines the methods to compose a draw
33   * primitive with the underlying graphics area.
34   * After the <code>Composite</code> is set in the
35   * {@link Graphics2D} context, it combines a shape, text, or an image
36   * being rendered with the colors that have already been rendered
37   * according to pre-defined rules. The classes
38   * implementing this interface provide the rules and a method to create
39   * the context for a particular operation.
40   * <code>CompositeContext</code> is an environment used by the
41   * compositing operation, which is created by the <code>Graphics2D</code>
42   * prior to the start of the operation.  <code>CompositeContext</code>
43   * contains private information and resources needed for a compositing
44   * operation.  When the <code>CompositeContext</code> is no longer needed,
45   * the <code>Graphics2D</code> object disposes of it in order to reclaim
46   * resources allocated for the operation.
47   * <p>
48   * Instances of classes implementing <code>Composite</code> must be
49   * immutable because the <code>Graphics2D</code> does not clone
50   * these objects when they are set as an attribute with the
51   * <code>setComposite</code> method or when the <code>Graphics2D</code>
52   * object is cloned.  This is to avoid undefined rendering behavior of
53   * <code>Graphics2D</code>, resulting from the modification of
54   * the <code>Composite</code> object after it has been set in the
55   * <code>Graphics2D</code> context.
56   * <p>
57   * Since this interface must expose the contents of pixels on the
58   * target device or image to potentially arbitrary code, the use of
59   * custom objects which implement this interface when rendering directly
60   * to a screen device is governed by the <code>readDisplayPixels</code>
61   * {@link AWTPermission}.  The permission check will occur when such
62   * a custom object is passed to the <code>setComposite</code> method
63   * of a <code>Graphics2D</code> retrieved from a {@link Component}.
64   * @see AlphaComposite
65   * @see CompositeContext
66   * @see Graphics2D#setComposite
67   */
68  public interface Composite {
69  
70      /**
71       * Creates a context containing state that is used to perform
72       * the compositing operation.  In a multi-threaded environment,
73       * several contexts can exist simultaneously for a single
74       * <code>Composite</code> object.
75       * @param srcColorModel  the {@link ColorModel} of the source
76       * @param dstColorModel  the <code>ColorModel</code> of the destination
77       * @param hints the hint that the context object uses to choose between
78       * rendering alternatives
79       * @return the <code>CompositeContext</code> object used to perform the
80       * compositing operation.
81       */
82      public CompositeContext createContext(ColorModel srcColorModel,
83                                            ColorModel dstColorModel,
84                                            RenderingHints hints);
85  
86  }