ImageObserver


1   /*
2    * @(#)ImageObserver.java   1.27 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.awt.image;
9   
10  import java.awt.Image  ;
11  
12  /**
13   * An asynchronous update interface for receiving notifications about
14   * Image information as the Image is constructed.
15   *
16   * @version     1.27 12/19/03
17   * @author  Jim Graham
18   */
19  public interface ImageObserver {
20      /**
21       * This method is called when information about an image which was
22       * previously requested using an asynchronous interface becomes
23       * available.  Asynchronous interfaces are method calls such as
24       * getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver)
25       * which take an ImageObserver object as an argument.  Those methods
26       * register the caller as interested either in information about
27       * the overall image itself (in the case of getWidth(ImageObserver))
28       * or about an output version of an image (in the case of the
29       * drawImage(img, x, y, [w, h,] ImageObserver) call).  
30       *
31       * <p>This method
32       * should return true if further updates are needed or false if the
33       * required information has been acquired.  The image which was being
34       * tracked is passed in using the img argument.  Various constants
35       * are combined to form the infoflags argument which indicates what
36       * information about the image is now available.  The interpretation
37       * of the x, y, width, and height arguments depends on the contents
38       * of the infoflags argument.
39       * <p>
40       * The <code>infoflags</code> argument should be the bitwise inclusive 
41       * <b>OR</b> of the following flags: <code>WIDTH</code>, 
42       * <code>HEIGHT</code>, <code>PROPERTIES</code>, <code>SOMEBITS</code>, 
43       * <code>FRAMEBITS</code>, <code>ALLBITS</code>, <code>ERROR</code>, 
44       * <code>ABORT</code>.
45       *
46       * @param     img   the image being observed.
47       * @param     infoflags   the bitwise inclusive OR of the following 
48       *               flags:  <code>WIDTH</code>, <code>HEIGHT</code>, 
49       *               <code>PROPERTIES</code>, <code>SOMEBITS</code>,
50       *               <code>FRAMEBITS</code>, <code>ALLBITS</code>, 
51       *               <code>ERROR</code>, <code>ABORT</code>. 
52       * @param     x   the <i>x</i> coordinate.
53       * @param     y   the <i>y</i> coordinate.
54       * @param     width    the width.
55       * @param     height   the height.
56       * @return    <code>false</code> if the infoflags indicate that the
57       *            image is completely loaded; <code>true</code> otherwise.
58       * 
59       * @see #WIDTH
60       * @see #HEIGHT
61       * @see #PROPERTIES
62       * @see #SOMEBITS
63       * @see #FRAMEBITS
64       * @see #ALLBITS
65       * @see #ERROR
66       * @see #ABORT
67       * @see Image#getWidth
68       * @see Image#getHeight
69       * @see java.awt.Graphics#drawImage
70       */
71      public boolean imageUpdate(Image   img, int infoflags,
72                     int x, int y, int width, int height);
73  
74      /**
75       * This flag in the infoflags argument to imageUpdate indicates that 
76       * the width of the base image is now available and can be taken
77       * from the width argument to the imageUpdate callback method.
78       * @see Image#getWidth
79       * @see #imageUpdate
80       */
81      public static final int WIDTH = 1;
82  
83      /**
84       * This flag in the infoflags argument to imageUpdate indicates that 
85       * the height of the base image is now available and can be taken
86       * from the height argument to the imageUpdate callback method.
87       * @see Image#getHeight
88       * @see #imageUpdate
89       */
90      public static final int HEIGHT = 2;
91  
92      /**
93       * This flag in the infoflags argument to imageUpdate indicates that 
94       * the properties of the image are now available.
95       * @see Image#getProperty
96       * @see #imageUpdate
97       */
98      public static final int PROPERTIES = 4;
99  
100     /**
101      * This flag in the infoflags argument to imageUpdate indicates that 
102      * more pixels needed for drawing a scaled variation of the image
103      * are available.  The bounding box of the new pixels can be taken
104      * from the x, y, width, and height arguments to the imageUpdate
105      * callback method.
106      * @see java.awt.Graphics#drawImage
107      * @see #imageUpdate
108      */
109     public static final int SOMEBITS = 8;
110 
111     /**
112      * This flag in the infoflags argument to imageUpdate indicates that 
113      * another complete frame of a multi-frame image which was previously
114      * drawn is now available to be drawn again.  The x, y, width, and height
115      * arguments to the imageUpdate callback method should be ignored.
116      * @see java.awt.Graphics#drawImage
117      * @see #imageUpdate
118      */
119     public static final int FRAMEBITS = 16;
120 
121     /**
122      * This flag in the infoflags argument to imageUpdate indicates that 
123      * a static image which was previously drawn is now complete and can
124      * be drawn again in its final form.  The x, y, width, and height
125      * arguments to the imageUpdate callback method should be ignored.
126      * @see java.awt.Graphics#drawImage
127      * @see #imageUpdate
128      */
129     public static final int ALLBITS = 32;
130 
131     /**
132      * This flag in the infoflags argument to imageUpdate indicates that 
133      * an image which was being tracked asynchronously has encountered
134      * an error.  No further information will become available and
135      * drawing the image will fail.
136      * As a convenience, the ABORT flag will be indicated at the same
137      * time to indicate that the image production was aborted.
138      * @see #imageUpdate
139      */
140     public static final int ERROR = 64;
141 
142     /**
143      * This flag in the infoflags argument to imageUpdate indicates that 
144      * an image which was being tracked asynchronously was aborted before
145      * production was complete.  No more information will become available
146      * without further action to trigger another image production sequence.
147      * If the ERROR flag was not also set in this image update, then
148      * accessing any of the data in the image will restart the production
149      * again, probably from the beginning.
150      * @see #imageUpdate
151      */
152     public static final int ABORT = 128;
153 }
154
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