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