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} 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} 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} is an environment used by the
  41  * compositing operation, which is created by the {@code Graphics2D}
  42  * prior to the start of the operation.  {@code CompositeContext}
  43  * contains private information and resources needed for a compositing
  44  * operation.  When the {@code CompositeContext} is no longer needed,
  45  * the {@code Graphics2D} object disposes of it in order to reclaim
  46  * resources allocated for the operation.
  47  * <p>
  48  * Instances of classes implementing {@code Composite} must be
  49  * immutable because the {@code Graphics2D} does not clone
  50  * these objects when they are set as an attribute with the
  51  * {@code setComposite} method or when the {@code Graphics2D}
  52  * object is cloned.  This is to avoid undefined rendering behavior of
  53  * {@code Graphics2D}, resulting from the modification of
  54  * the {@code Composite} object after it has been set in the
  55  * {@code Graphics2D} 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}
  61  * {@link AWTPermission}.  The permission check will occur when such
  62  * a custom object is passed to the {@code setComposite} method
  63  * of a {@code Graphics2D} 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} object.
  75      * @param srcColorModel  the {@link ColorModel} of the source
  76      * @param dstColorModel  the {@code ColorModel} of the destination
  77      * @param hints the hint that the context object uses to choose between
  78      * rendering alternatives
  79      * @return the {@code CompositeContext} object used to perform the
  80      * compositing operation.
  81      */
  82     public CompositeContext createContext(ColorModel srcColorModel,
  83                                           ColorModel dstColorModel,
  84                                           RenderingHints hints);
  85 
  86 }