ImageFilter


1   /*
2    * @(#)ImageFilter.java 1.31 04/07/16
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.util.Hashtable  ;
11  
12  /**
13   * This class implements a filter for the set of interface methods that
14   * are used to deliver data from an ImageProducer to an ImageConsumer.
15   * It is meant to be used in conjunction with a FilteredImageSource
16   * object to produce filtered versions of existing images.  It is a
17   * base class that provides the calls needed to implement a "Null filter"
18   * which has no effect on the data being passed through.  Filters should
19   * subclass this class and override the methods which deal with the
20   * data that needs to be filtered and modify it as necessary.
21   *
22   * @see FilteredImageSource
23   * @see ImageConsumer
24   *
25   * @version 1.31 07/16/04
26   * @author  Jim Graham
27   */
28  public class ImageFilter implements ImageConsumer  , Cloneable   {
29      /**
30       * The consumer of the particular image data stream for which this
31       * instance of the ImageFilter is filtering data.  It is not
32       * initialized during the constructor, but rather during the
33       * getFilterInstance() method call when the FilteredImageSource
34       * is creating a unique instance of this object for a particular
35       * image data stream.
36       * @see #getFilterInstance
37       * @see ImageConsumer
38       */
39      protected ImageConsumer   consumer;
40  
41      /**
42       * Returns a unique instance of an ImageFilter object which will
43       * actually perform the filtering for the specified ImageConsumer.
44       * The default implementation just clones this object.
45       * <p>
46       * Note: This method is intended to be called by the ImageProducer
47       * of the Image whose pixels are being filtered.  Developers using
48       * this class to filter pixels from an image should avoid calling
49       * this method directly since that operation could interfere
50       * with the filtering operation.
51       * @param ic the specified <code>ImageConsumer</code>
52       * @return an <code>ImageFilter</code> used to perform the 
53       *         filtering for the specified <code>ImageConsumer</code>.
54       */
55      public ImageFilter   getFilterInstance(ImageConsumer   ic) {
56      ImageFilter   instance = (ImageFilter  ) clone();
57      instance.consumer = ic;
58      return instance;
59      }
60  
61      /**
62       * Filters the information provided in the setDimensions method
63       * of the ImageConsumer interface.
64       * <p>
65       * Note: This method is intended to be called by the ImageProducer
66       * of the Image whose pixels are being filtered.  Developers using
67       * this class to filter pixels from an image should avoid calling
68       * this method directly since that operation could interfere      
69       * with the filtering operation.  
70       * @see ImageConsumer#setDimensions
71       */
72      public void setDimensions(int width, int height) {
73      consumer.setDimensions(width, height);
74      }
75  
76      /**
77       * Passes the properties from the source object along after adding a
78       * property indicating the stream of filters it has been run through.
79       * <p>
80       * Note: This method is intended to be called by the ImageProducer
81       * of the Image whose pixels are being filtered.  Developers using
82       * this class to filter pixels from an image should avoid calling
83       * this method directly since that operation could interfere      
84       * with the filtering operation.  
85       *
86       * @param props the properties from the source object
87       * @exception NullPointerException if <code>props</code> is null
88       */
89      public void setProperties(Hashtable  <?,?> props) {
90      Hashtable  <Object  ,Object  > p = (Hashtable  <Object  ,Object  >)props.clone();
91      Object   o = p.get("filters");
92      if (o == null) {
93          p.put("filters", toString());
94      } else if (o instanceof String  ) {
95          p.put("filters", ((String  ) o)+toString());
96      }
97      consumer.setProperties(p);
98      }
99  
100     /**
101      * Filter the information provided in the setColorModel method
102      * of the ImageConsumer interface.
103      * <p>
104      * Note: This method is intended to be called by the ImageProducer
105      * of the Image whose pixels are being filtered.  Developers using
106      * this class to filter pixels from an image should avoid calling
107      * this method directly since that operation could interfere      
108      * with the filtering operation.  
109      * @see ImageConsumer#setColorModel
110      */
111     public void setColorModel(ColorModel   model) {
112     consumer.setColorModel(model);
113     }
114 
115     /**
116      * Filters the information provided in the setHints method
117      * of the ImageConsumer interface.
118      * <p>
119      * Note: This method is intended to be called by the ImageProducer
120      * of the Image whose pixels are being filtered.  Developers using
121      * this class to filter pixels from an image should avoid calling
122      * this method directly since that operation could interfere      
123      * with the filtering operation.  
124      * @see ImageConsumer#setHints
125      */
126     public void setHints(int hints) {
127     consumer.setHints(hints);
128     }
129 
130     /**
131      * Filters the information provided in the setPixels method of the
132      * ImageConsumer interface which takes an array of bytes.
133      * <p>
134      * Note: This method is intended to be called by the ImageProducer
135      * of the Image whose pixels are being filtered.  Developers using
136      * this class to filter pixels from an image should avoid calling
137      * this method directly since that operation could interfere      
138      * with the filtering operation.  
139      * @see ImageConsumer#setPixels
140      */
141     public void setPixels(int x, int y, int w, int h,
142               ColorModel   model, byte pixels[], int off,
143               int scansize) {
144     consumer.setPixels(x, y, w, h, model, pixels, off, scansize);
145     }
146 
147     /**
148      * Filters the information provided in the setPixels method of the
149      * ImageConsumer interface which takes an array of integers.
150      * <p>
151      * Note: This method is intended to be called by the ImageProducer
152      * of the Image whose pixels are being filtered.  Developers using
153      * this class to filter pixels from an image should avoid calling
154      * this method directly since that operation could interfere      
155      * with the filtering operation.  
156      * @see ImageConsumer#setPixels
157      */
158     public void setPixels(int x, int y, int w, int h,
159               ColorModel   model, int pixels[], int off,
160               int scansize) {
161     consumer.setPixels(x, y, w, h, model, pixels, off, scansize);
162     }
163 
164     /**
165      * Filters the information provided in the imageComplete method of
166      * the ImageConsumer interface.
167      * <p>
168      * Note: This method is intended to be called by the ImageProducer
169      * of the Image whose pixels are being filtered.  Developers using
170      * this class to filter pixels from an image should avoid calling
171      * this method directly since that operation could interfere      
172      * with the filtering operation.  
173      * @see ImageConsumer#imageComplete
174      */
175     public void imageComplete(int status) {
176     consumer.imageComplete(status);
177     }
178 
179     /**
180      * Responds to a request for a TopDownLeftRight (TDLR) ordered resend
181      * of the pixel data from an <code>ImageConsumer</code>.
182      * When an <code>ImageConsumer</code> being fed
183      * by an instance of this <code>ImageFilter</code>
184      * requests a resend of the data in TDLR order, 
185      * the <code>FilteredImageSource</code>
186      * invokes this method of the <code>ImageFilter</code>.
187      *
188      * <p>
189      *
190      * An <code>ImageFilter</code> subclass might override this method or not,
191      * depending on if and how it can send data in TDLR order.
192      * Three possibilities exist:
193      *
194      * <ul>
195      * <li>
196      * Do not override this method.
197      * This makes the subclass use the default implementation,
198      * which is to 
199      * forward the request
200      * to the indicated <code>ImageProducer</code>
201      * using this filter as the requesting <code>ImageConsumer</code>.
202      * This behavior
203      * is appropriate if the filter can determine
204      * that it will forward the pixels
205      * in TDLR order if its upstream producer object
206      * sends them in TDLR order.
207      *
208      * <li>
209      * Override the method to simply send the data.
210      * This is appropriate if the filter can handle the request itself &#151;
211      * for example,
212      * if the generated pixels have been saved in some sort of buffer.
213      *
214      * <li>
215      * Override the method to do nothing.
216      * This is appropriate 
217      * if the filter cannot produce filtered data in TDLR order.
218      * </ul> 
219      *
220      * @see ImageProducer#requestTopDownLeftRightResend
221      * @param ip the ImageProducer that is feeding this instance of
222      * the filter - also the ImageProducer that the request should be
223      * forwarded to if necessary
224      * @exception NullPointerException if <code>ip</code> is null
225      */
226     public void resendTopDownLeftRight(ImageProducer   ip) {
227     ip.requestTopDownLeftRightResend(this);
228     }
229     
230     /**
231      * Clones this object.
232      */
233     public Object   clone() { 
234     try { 
235         return super.clone();
236     } catch (CloneNotSupportedException   e) { 
237         // this shouldn't happen, since we are Cloneable
238         throw new InternalError  ();
239     }
240     }
241 }
242
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