001 /* Image.java -- superclass for images
002 Copyright (C) 1999, 2002, 2004, 2005, 2006 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.awt;
040
041 import java.awt.image.AreaAveragingScaleFilter;
042 import java.awt.image.FilteredImageSource;
043 import java.awt.image.ImageFilter;
044 import java.awt.image.ImageObserver;
045 import java.awt.image.ImageProducer;
046 import java.awt.image.ReplicateScaleFilter;
047
048 /**
049 * This is the abstract superclass of all image objects in Java.
050 *
051 * @author Aaron M. Renn (arenn@urbanophile.com)
052 * @since 1.0
053 * @status updated to 1.5
054 */
055 public abstract class Image
056 {
057 /**
058 * This variable is returned whenever a property that is not defined
059 * is requested.
060 */
061 // For debug purposes, this might as well be a unique string.
062 public static final Object UndefinedProperty
063 = new String("undefined property");
064
065 /**
066 * Constant indicating that the default scaling algorithm should be used.
067 *
068 * @since 1.1
069 */
070 public static final int SCALE_DEFAULT = 1;
071
072 /**
073 * Constant indicating that a fast scaling algorithm should be used.
074 *
075 * @since 1.1
076 */
077 public static final int SCALE_FAST = 2;
078
079 /**
080 * Constant indicating that a smooth scaling algorithm should be used.
081 *
082 * @since 1.1
083 */
084 public static final int SCALE_SMOOTH = 4;
085
086 /**
087 * Constant indicating that the <code>ReplicateScaleFilter</code> class
088 * algorithm should be used for scaling.
089 *
090 * @see ReplicateScaleFilter
091 * @since 1.1
092 */
093 public static final int SCALE_REPLICATE = 8;
094
095 /**
096 * Constant indicating that the area averaging scaling algorithm should be
097 * used.
098 *
099 * @see java.awt.image.AreaAveragingScaleFilter
100 * @since 1.1
101 */
102 public static final int SCALE_AREA_AVERAGING = 16;
103
104 /**
105 * The acceleration priority of the image
106 * @since 1.5
107 */
108 protected float accelerationPriority;
109
110 /**
111 * A default constructor for subclasses.
112 */
113 public Image()
114 {
115 }
116
117 /**
118 * Returns the width of the image, or -1 if it is unknown. If the
119 * image width is unknown, the observer object will be notified when
120 * the value is known.
121 *
122 * @param observer the image observer for this object
123 * @return the width in pixels
124 * @see #getHeight(ImageObserver)
125 */
126 public abstract int getWidth(ImageObserver observer);
127
128 /**
129 * Returns the height of the image, or -1 if it is unknown. If the
130 * image height is unknown, the observer object will be notified when
131 * the value is known.
132 *
133 * @param observer the image observer for this object
134 * @return the height in pixels
135 * @see #getWidth(ImageObserver)
136 */
137 public abstract int getHeight(ImageObserver observer);
138
139 /**
140 * Returns the image producer object for this object. The producer is the
141 * object which generates pixels for this image.
142 *
143 * @return the image producer for this object
144 */
145 public abstract ImageProducer getSource();
146
147 /**
148 * Returns a graphics context object for drawing an off-screen object.
149 * This method is only valid for off-screen objects.
150 *
151 * @return a graphics context object for an off-screen object
152 */
153 public abstract Graphics getGraphics();
154
155 /**
156 * This method requests a named property for an object. The value of the
157 * property is returned. The value <code>UndefinedProperty</code> is
158 * returned if there is no property with the specified name. The value
159 * <code>null</code> is returned if the properties for the object are
160 * not yet known. In this case, the specified image observer is notified
161 * when the properties are known.
162 *
163 * @param name the requested property name
164 * @param observer the image observer for this object
165 * @return the named property, if available
166 * @see #UndefinedProperty
167 */
168 public abstract Object getProperty(String name, ImageObserver observer);
169
170 /**
171 * Scales the image to the requested dimension. A new Image with asynchronous
172 * loading will be produced according to the hints of the algorithm
173 * requested. If either the width or height is non-positive, it is adjusted
174 * to preserve the original aspect ratio.
175 * If an illegal value of <code>flags</code> is passed,
176 * the default algorithm is used.
177 *
178 * @param width the width of the scaled image
179 * @param height the height of the scaled image
180 * @param flags a value indicating the algorithm to use
181 * @return the scaled <code>Image</code> object
182 * @see #SCALE_DEFAULT
183 * @see #SCALE_FAST
184 * @see #SCALE_SMOOTH
185 * @see #SCALE_REPLICATE
186 * @see #SCALE_AREA_AVERAGING
187 * @since 1.1
188 */
189 public Image getScaledInstance(int width, int height, int flags)
190 {
191 ImageFilter filter;
192 switch (flags)
193 {
194 case SCALE_AREA_AVERAGING:
195 case SCALE_SMOOTH:
196 filter = new AreaAveragingScaleFilter(width, height);
197 break;
198 case SCALE_DEFAULT:
199 case SCALE_FAST:
200 case SCALE_REPLICATE:
201 default:
202 filter = new ReplicateScaleFilter(width, height);
203 }
204
205 ImageProducer producer = new FilteredImageSource(getSource(), filter);
206 return Toolkit.getDefaultToolkit().createImage(producer);
207 }
208
209 /**
210 * Flushes (that is, destroys) any resources used for this image. This
211 * includes the actual image data.
212 */
213 public abstract void flush();
214
215 /**
216 * Sets the acceleration priority of the image.
217 * This is a value from 0 (lowest) to 1 (highest), which may
218 * be used as a hint for image acceleration.
219 * E.g. higher priority images may be stored in video memory.
220 * @param priority - the priority
221 * @throws IllegalArgumentException if priority is not >= 0 and <= 1.
222 *
223 * @since 1.5
224 */
225 public void setAccelerationPriority(float priority)
226 {
227 if( priority < 0f || priority > 1f)
228 throw new IllegalArgumentException("Invalid priority value.");
229 accelerationPriority = priority;
230 }
231
232 /**
233 * Returns the acceleration priority of the image.
234 *
235 * @see #setAccelerationPriority(float)
236 * @since 1.5
237 */
238 public float getAccelerationPriority()
239 {
240 return accelerationPriority;
241 }
242 } // class Image