libjava/classpath/java/awt/Image.java

   1 /* Image.java -- superclass for images
   2    Copyright (C) 1999, 2002, 2004, 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., 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 java.awt.image.AreaAveragingScaleFilter;
  42 import java.awt.image.FilteredImageSource;
  43 import java.awt.image.ImageFilter;
  44 import java.awt.image.ImageObserver;
  45 import java.awt.image.ImageProducer;
  46 import java.awt.image.ReplicateScaleFilter;
  47
  48 /**
  49  * This is the abstract superclass of all image objects in Java.
  50  *
  51  * @author Aaron M. Renn (arenn@urbanophile.com)
  52  * @since 1.0
  53  * @status updated to 1.4
  54  */
  55 public abstract class Image
  56 {
  57   /**
  58    * This variable is returned whenever a property that is not defined
  59    * is requested.
  60    */
  61   // For debug purposes, this might as well be a unique string.
  62   public static final Object UndefinedProperty
  63     = new String("undefined property");
  64
  65   /**
  66    * Constant indicating that the default scaling algorithm should be used.
  67    *
  68    * @since 1.1
  69    */
  70   public static final int SCALE_DEFAULT = 1;
  71
  72   /**
  73    * Constant indicating that a fast scaling algorithm should be used.
  74    *
  75    * @since 1.1
  76    */
  77   public static final int SCALE_FAST = 2;
  78
  79   /**
  80    * Constant indicating that a smooth scaling algorithm should be used.
  81    *
  82    * @since 1.1
  83    */
  84   public static final int SCALE_SMOOTH = 4;
  85
  86   /**
  87    * Constant indicating that the <code>ReplicateScaleFilter</code> class
  88    * algorithm should be used for scaling.
  89    *
  90    * @see ReplicateScaleFilter
  91    * @since 1.1
  92    */
  93   public static final int SCALE_REPLICATE = 8;
  94
  95   /**
  96    * Constant indicating that the area averaging scaling algorithm should be
  97    * used.
  98    *
  99    * @see java.awt.image.AreaAveragingScaleFilter
 100    * @since 1.1
 101    */
 102   public static final int SCALE_AREA_AVERAGING = 16;
 103
 104   /**
 105    * A default constructor for subclasses.
 106    */
 107   public Image()
 108   {
 109   }
 110
 111   /**
 112    * Returns the width of the image, or -1 if it is unknown.  If the
 113    * image width is unknown, the observer object will be notified when
 114    * the value is known.
 115    *
 116    * @param observer the image observer for this object
 117    * @return the width in pixels
 118    * @see #getHeight(ImageObserver)
 119    */
 120   public abstract int getWidth(ImageObserver observer);
 121
 122   /**
 123    * Returns the height of the image, or -1 if it is unknown.  If the
 124    * image height is unknown, the observer object will be notified when
 125    * the value is known.
 126    *
 127    * @param observer the image observer for this object
 128    * @return the height in pixels
 129    * @see #getWidth(ImageObserver)
 130    */
 131   public abstract int getHeight(ImageObserver observer);
 132
 133   /**
 134    * Returns the image producer object for this object. The producer is the
 135    * object which generates pixels for this image.
 136    *
 137    * @return the image producer for this object
 138    */
 139   public abstract ImageProducer getSource();
 140
 141   /**
 142    * Returns a graphics context object for drawing an off-screen object.
 143    * This method is only valid for off-screen objects.
 144    *
 145    * @return a graphics context object for an off-screen object
 146    */
 147   public abstract Graphics getGraphics();
 148
 149   /**
 150    * This method requests a named property for an object.  The value of the
 151    * property is returned. The value <code>UndefinedProperty</code> is
 152    * returned if there is no property with the specified name.  The value
 153    * <code>null</code> is returned if the properties for the object are
 154    * not yet known.  In this case, the specified image observer is notified
 155    * when the properties are known.
 156    *
 157    * @param name the requested property name
 158    * @param observer the image observer for this object
 159    * @return the named property, if available
 160    * @see #UndefinedProperty
 161    */
 162   public abstract Object getProperty(String name, ImageObserver observer);
 163
 164   /**
 165    * Scales the image to the requested dimension. A new Image with asynchronous
 166    * loading will be produced according to the hints of the algorithm
 167    * requested. If either the width or height is non-positive, it is adjusted
 168    * to preserve the original aspect ratio.
 169    * If an illegal value of <code>flags</code> is passed,
 170    * the default algorithm is used.
 171    *
 172    * @param width the width of the scaled image
 173    * @param height the height of the scaled image
 174    * @param flags a value indicating the algorithm to use
 175    * @return the scaled <code>Image</code> object
 176    * @see #SCALE_DEFAULT
 177    * @see #SCALE_FAST
 178    * @see #SCALE_SMOOTH
 179    * @see #SCALE_REPLICATE
 180    * @see #SCALE_AREA_AVERAGING
 181    * @since 1.1
 182    */
 183   public Image getScaledInstance(int width, int height, int flags)
 184   {
 185     ImageFilter filter;
 186     switch (flags)
 187     {
 188       case SCALE_AREA_AVERAGING:
 189       case SCALE_SMOOTH:
 190         filter = new AreaAveragingScaleFilter(width, height);
 191         break;
 192       case SCALE_DEFAULT:
 193       case SCALE_FAST:
 194       case SCALE_REPLICATE:
 195       default:
 196         filter = new ReplicateScaleFilter(width, height);
 197     }
 198
 199     ImageProducer producer = new FilteredImageSource(getSource(), filter);
 200     return Toolkit.getDefaultToolkit().createImage(producer);
 201   }
 202
 203   /**
 204    * Flushes (that is, destroys) any resources used for this image.  This
 205    * includes the actual image data.
 206    */
 207   public abstract void flush();
 208 } // class Image