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    1   /*
    2    * Copyright (c) 1997, 1998, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    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
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   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   }

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