01: /*
02: * $Id: RefImage.java,v 1.2 2007/12/20 18:17:41 rbair Exp $
03: *
04: * Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
05: * Santa Clara, California 95054, U.S.A. All rights reserved.
06: *
07: * This library is free software; you can redistribute it and/or
08: * modify it under the terms of the GNU Lesser General Public
09: * License as published by the Free Software Foundation; either
10: * version 2.1 of the License, or (at your option) any later version.
11: *
12: * This library is distributed in the hope that it will be useful,
13: * but WITHOUT ANY WARRANTY; without even the implied warranty of
14: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15: * Lesser General Public License for more details.
16: *
17: * You should have received a copy of the GNU Lesser General Public
18: * License along with this library; if not, write to the Free Software
19: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20: */
21:
22: package com.sun.pdfview;
23:
24: import java.awt.Graphics2D;
25: import java.awt.image.BufferedImage;
26:
27: /**
28: * A BufferedImage subclass that holds a strong reference to its graphics
29: * object. This means that the graphics will never go away as long as
30: * someone holds a reference to this image, and createGraphics() and
31: * getGraphics() can be called multiple times safely, and will always return
32: * the same graphics object.
33: */
34: public class RefImage extends BufferedImage {
35: /** a strong reference to the graphics object */
36: private Graphics2D g;
37:
38: /** Creates a new instance of RefImage */
39: public RefImage(int width, int height, int type) {
40: super (width, height, type);
41: }
42:
43: /**
44: * Create a graphics object only if it is currently null, otherwise
45: * return the existing graphics object.
46: */
47: public Graphics2D createGraphics() {
48: if (g == null) {
49: g = super.createGraphics();
50: }
51:
52: return g;
53: }
54:
55: }
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