Source for java.awt.Image

   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:    *
 170:    * @param width the width of the scaled image
 171:    * @param height the height of the scaled image
 172:    * @param flags a value indicating the algorithm to use
 173:    * @return the scaled <code>Image</code> object
 174:    * @see #SCALE_DEFAULT
 175:    * @see #SCALE_FAST
 176:    * @see #SCALE_SMOOTH
 177:    * @see #SCALE_REPLICATE
 178:    * @see #SCALE_AREA_AVERAGING
 179:    * @since 1.1
 180:    */
 181:   public Image getScaledInstance(int width, int height, int flags)
 182:   {
 183:     ImageFilter filter;
 184:     switch (flags)
 185:     {
 186:       case SCALE_DEFAULT:
 187:       case SCALE_FAST:
 188:       case SCALE_REPLICATE:
 189:     filter = new ReplicateScaleFilter(width, height);
 190:     break;
 191:       case SCALE_AREA_AVERAGING:
 192:     filter = new AreaAveragingScaleFilter(width, height);
 193:     break;
 194:       case SCALE_SMOOTH:
 195:         throw new Error("SCALE_SMOOTH: not implemented");
 196:       default:
 197:         throw new Error("Unknown flag or not implemented: " + flags);
 198:     }
 199: 
 200:     ImageProducer producer = new FilteredImageSource(getSource(), filter);
 201:     return Toolkit.getDefaultToolkit().createImage(producer);
 202:   }
 203: 
 204:   /**
 205:    * Flushes (that is, destroys) any resources used for this image.  This
 206:    * includes the actual image data.
 207:    */
 208:   public abstract void flush();
 209: } // class Image