Source for java.awt.AlphaComposite

   1: /* AlphaComposite.java -- provides a context for performing alpha compositing
   2:    Copyright (C) 2002, 2005, 2006  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., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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 gnu.java.awt.java2d.AlphaCompositeContext;
  42: 
  43: import java.awt.image.ColorModel;
  44: import java.util.LinkedHashMap;
  45: import java.util.Map;
  46: 
  47: /**
  48:  *
  49:  * @author Eric Blake (ebb9@email.byu.edu)
  50:  * @see Composite
  51:  * @see CompositeContext
  52:  * @since 1.3
  53:  * @status updated to 1.4 except for createContext, needs documentation
  54:  */
  55: public final class AlphaComposite implements Composite
  56: {
  57:   /** Map Long to AlphaComposites. See getInstance for details. */
  58:   private static final LinkedHashMap cache = new LinkedHashMap(11, 0.75f, true)
  59:   {
  60:     /** The largest the alpha composite cache can grow. */
  61:     private static final int MAX_CACHE_SIZE = 2048;
  62: 
  63:     /** Prune stale entries. */
  64:     protected boolean removeEldestEntry(Entry eldest)
  65:     {
  66:       return size() > MAX_CACHE_SIZE;
  67:     }
  68:   };
  69: 
  70:   public static final int CLEAR = 1;
  71:   public static final int SRC = 2;
  72:   public static final int DST = 9;
  73:   public static final int SRC_OVER = 3;
  74:   public static final int DST_OVER = 4;
  75:   public static final int SRC_IN = 5;
  76:   public static final int DST_IN = 6;
  77:   public static final int SRC_OUT = 7;
  78:   public static final int DST_OUT = 8;
  79:   public static final int SRC_ATOP = 10;
  80:   public static final int DST_ATOP = 11;
  81:   public static final int XOR = 12;
  82:   public static final AlphaComposite Clear = getInstance(CLEAR);
  83:   public static final AlphaComposite Src = getInstance(SRC);
  84:   public static final AlphaComposite Dst = getInstance(DST);
  85:   public static final AlphaComposite SrcOver = getInstance(SRC_OVER);
  86:   public static final AlphaComposite DstOver = getInstance(DST_OVER);
  87:   public static final AlphaComposite SrcIn = getInstance(SRC_IN);
  88:   public static final AlphaComposite DstIn = getInstance(DST_IN);
  89:   public static final AlphaComposite SrcOut = getInstance(SRC_OUT);
  90:   public static final AlphaComposite DstOut = getInstance(DST_OUT);
  91:   public static final AlphaComposite SrcAtop = getInstance(SRC_ATOP);
  92:   public static final AlphaComposite DstAtop = getInstance(DST_ATOP);
  93:   public static final AlphaComposite Xor = getInstance(XOR);
  94:   
  95:   private final int rule;
  96:   private final float alpha;
  97:   private AlphaComposite(int rule, float alpha)
  98:   {
  99:     this.rule = rule;
 100:     this.alpha = alpha;
 101:   }
 102: 
 103:   /**
 104:    * Creates an AlphaComposite object with the specified rule.
 105:    *
 106:    * @param rule The compositing rule.
 107:    *
 108:    * @exception IllegalArgumentException If rule is not one of the following:
 109:    * CLEAR, SRC, DST, SRC_OVER, DST_OVER, SRC_IN, DST_IN, SRC_OUT, DST_OUT,
 110:    * SRC_ATOP, DST_ATOP, or XOR.
 111:    */
 112:   public static AlphaComposite getInstance(int rule)
 113:   {
 114:     return getInstance(rule, 1);
 115:   }
 116:   
 117:   /**
 118:    * Creates an AlphaComposite object with the specified rule and the constant
 119:    * alpha to multiply with the alpha of the source. The source is multiplied
 120:    * with the specified alpha before being composited with the destination.
 121:    *
 122:    * @param rule The compositing rule.
 123:    *
 124:    * @exception IllegalArgumentException If rule is not one of the following:
 125:    * CLEAR, SRC, DST, SRC_OVER, DST_OVER, SRC_IN, DST_IN, SRC_OUT, DST_OUT,
 126:    * SRC_ATOP, DST_ATOP, or XOR.
 127:    */
 128:   public static AlphaComposite getInstance(int rule, float alpha)
 129:   {
 130:     if (rule < CLEAR || rule > XOR || ! (alpha >= 0 && alpha <= 1))
 131:       throw new IllegalArgumentException();
 132:     // This long is guaranteed unique for all valid alpha composites.
 133:     Long l = new Long(rule + Double.doubleToLongBits(alpha));
 134:     AlphaComposite a = (AlphaComposite) cache.get(l);
 135:     if (a == null)
 136:       {
 137:         a = new AlphaComposite(rule, alpha);
 138:         cache.put(l, a);
 139:       }
 140:     return a;
 141:   }
 142: 
 143:   /**
 144:    * Creates a {@link CompositeContext} that can be used to perform
 145:    * compositing operations according to this AlphaComposite settings.
 146:    *
 147:    * @param srcColorModel the color model of the source raster
 148:    * @param dstColorModel the color model of the destination raster
 149:    * @param hints the rendering hints to use
 150:    *
 151:    * @return a {@link CompositeContext} that can be used to perform
 152:    *         compositing operations according to this AlphaComposite settings
 153:    */
 154:   public CompositeContext createContext(ColorModel srcColorModel,
 155:                                         ColorModel dstColorModel,
 156:                                         RenderingHints hints)
 157:   {
 158:     return new AlphaCompositeContext(this, srcColorModel, dstColorModel);
 159:   }
 160: 
 161:   public float getAlpha()
 162:   {
 163:     return alpha;
 164:   }
 165:   public int getRule()
 166:   {
 167:     return rule;
 168:   }
 169:   public int hashCode()
 170:   {
 171:     return 31 * Float.floatToIntBits(alpha) + rule;
 172:   }
 173:   public boolean equals(Object o)
 174:   {
 175:     if (! (o instanceof AlphaComposite))
 176:       return false;
 177:     AlphaComposite a = (AlphaComposite) o;
 178:     return rule == a.rule && alpha == a.alpha;
 179:   }
 180: } // class AlphaComposite