libjava/java/awt/AlphaComposite.java

   1 /* AlphaComposite.java -- provides a context for performing alpha compositing
   2    Copyright (C) 2002, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.awt;
  40
  41 import java.awt.image.ColorModel;
  42 import java.util.LinkedHashMap;
  43 import java.util.Map;
  44
  45 /**
  46  *
  47  * @author Eric Blake (ebb9@email.byu.edu)
  48  * @see Composite
  49  * @see CompositeContext
  50  * @since 1.3
  51  * @status updated to 1.4 except for createContext, needs documentation
  52  */
  53 public final class AlphaComposite implements Composite
  54 {
  55   /** Map Long to AlphaComposites. See getInstance for details. */
  56   private static final LinkedHashMap cache = new LinkedHashMap(11, 0.75f, true)
  57   {
  58     /** The largest the alpha composite cache can grow. */
  59     private static final int MAX_CACHE_SIZE = 2048;
  60
  61     /** Prune stale entries. */
  62     protected boolean removeEldestEntry(Map.Entry eldest)
  63     {   // XXX - FIXME Use Map.Entry, not just Entry as gcj 3.1 workaround.
  64       return size() > MAX_CACHE_SIZE;
  65     }
  66   };
  67
  68   public static final int CLEAR = 1;
  69   public static final int SRC = 2;
  70   public static final int DST = 9;
  71   public static final int SRC_OVER = 3;
  72   public static final int DST_OVER = 4;
  73   public static final int SRC_IN = 5;
  74   public static final int DST_IN = 6;
  75   public static final int SRC_OUT = 7;
  76   public static final int DST_OUT = 8;
  77   public static final int SRC_ATOP = 10;
  78   public static final int DST_ATOP = 11;
  79   public static final int XOR = 12;
  80   public static final AlphaComposite Clear = getInstance(CLEAR);
  81   public static final AlphaComposite Src = getInstance(SRC);
  82   public static final AlphaComposite Dst = getInstance(DST);
  83   public static final AlphaComposite SrcOver = getInstance(SRC_OVER);
  84   public static final AlphaComposite DstOver = getInstance(DST_OVER);
  85   public static final AlphaComposite SrcIn = getInstance(SRC_IN);
  86   public static final AlphaComposite DstIn = getInstance(DST_IN);
  87   public static final AlphaComposite SrcOut = getInstance(SRC_OUT);
  88   public static final AlphaComposite DstOut = getInstance(DST_OUT);
  89   public static final AlphaComposite SrcAtop = getInstance(SRC_ATOP);
  90   public static final AlphaComposite DstAtop = getInstance(DST_ATOP);
  91   public static final AlphaComposite Xor = getInstance(XOR);
  92
  93   private final int rule;
  94   private final float alpha;
  95   private AlphaComposite(int rule, float alpha)
  96   {
  97     this.rule = rule;
  98     this.alpha = alpha;
  99   }
 100
 101   /**
 102    * Creates an AlphaComposite object with the specified rule.
 103    *
 104    * @param rule The compositing rule.
 105    *
 106    * @exception IllegalArgumentException If rule is not one of the following:
 107    * CLEAR, SRC, DST, SRC_OVER, DST_OVER, SRC_IN, DST_IN, SRC_OUT, DST_OUT,
 108    * SRC_ATOP, DST_ATOP, or XOR.
 109    */
 110   public static AlphaComposite getInstance(int rule)
 111   {
 112     return getInstance(rule, 1);
 113   }
 114
 115   /**
 116    * Creates an AlphaComposite object with the specified rule and the constant
 117    * alpha to multiply with the alpha of the source. The source is multiplied
 118    * with the specified alpha before being composited with the destination.
 119    *
 120    * @param rule The compositing rule.
 121    *
 122    * @exception IllegalArgumentException If rule is not one of the following:
 123    * CLEAR, SRC, DST, SRC_OVER, DST_OVER, SRC_IN, DST_IN, SRC_OUT, DST_OUT,
 124    * SRC_ATOP, DST_ATOP, or XOR.
 125    */
 126   public static AlphaComposite getInstance(int rule, float alpha)
 127   {
 128     if (rule < CLEAR || rule > XOR || ! (alpha >= 0 && alpha <= 1))
 129       throw new IllegalArgumentException();
 130     // This long is guaranteed unique for all valid alpha composites.
 131     Long l = new Long(rule + Double.doubleToLongBits(alpha));
 132     AlphaComposite a = (AlphaComposite) cache.get(l);
 133     if (a == null)
 134       {
 135         a = new AlphaComposite(rule, alpha);
 136         cache.put(l, a);
 137       }
 138     return a;
 139   }
 140   public CompositeContext createContext(ColorModel srcColorModel,
 141                                         ColorModel dstColorModel,
 142                                         RenderingHints hints)
 143   {
 144     // XXX Implement. Sun uses undocumented implementation class
 145     // sun.java2d.SunCompositeContext.
 146     throw new Error("not implemented");
 147   }
 148   public float getAlpha()
 149   {
 150     return alpha;
 151   }
 152   public int getRule()
 153   {
 154     return rule;
 155   }
 156   public int hashCode()
 157   {
 158     return 31 * Float.floatToIntBits(alpha) + rule;
 159   }
 160   public boolean equals(Object o)
 161   {
 162     if (! (o instanceof AlphaComposite))
 163       return false;
 164     AlphaComposite a = (AlphaComposite) o;
 165     return rule == a.rule && alpha == a.alpha;
 166   }
 167 } // class AlphaComposite