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Java > Open Source Codes > org > apache > fop > image > analyser > GIFReader


1 /*
2  * $Id: GIFReader.java,v 1.3.2.1 2003/02/25 13:38:24 jeremias Exp $
3  * ============================================================================
4  * The Apache Software License, Version 1.1
5  * ============================================================================
6  *
7  * Copyright (C) 1999-2003 The Apache Software Foundation. All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without modifica-
10  * tion, are permitted provided that the following conditions are met:
11  *
12  * 1. Redistributions of source code must retain the above copyright notice,
13  * this list of conditions and the following disclaimer.
14  *
15  * 2. Redistributions in binary form must reproduce the above copyright notice,
16  * this list of conditions and the following disclaimer in the documentation
17  * and/or other materials provided with the distribution.
18  *
19  * 3. The end-user documentation included with the redistribution, if any, must
20  * include the following acknowledgment: "This product includes software
21  * developed by the Apache Software Foundation (http://www.apache.org/)."
22  * Alternately, this acknowledgment may appear in the software itself, if
23  * and wherever such third-party acknowledgments normally appear.
24  *
25  * 4. The names "FOP" and "Apache Software Foundation" must not be used to
26  * endorse or promote products derived from this software without prior
27  * written permission. For written permission, please contact
28  * apache@apache.org.
29  *
30  * 5. Products derived from this software may not be called "Apache", nor may
31  * "Apache" appear in their name, without prior written permission of the
32  * Apache Software Foundation.
33  *
34  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
35  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
36  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
37  * APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
38  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
39  * DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
40  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
41  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
42  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
43  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
44  * ============================================================================
45  *
46  * This software consists of voluntary contributions made by many individuals
47  * on behalf of the Apache Software Foundation and was originally created by
48  * James Tauber <jtauber@jtauber.com>. For more information on the Apache
49  * Software Foundation, please see <http://www.apache.org/>.
50  */
51 package org.apache.fop.image.analyser;
52
53 // Java
54 import java.io.BufferedInputStream JavaDoc;
55 import java.io.IOException JavaDoc;
56
57 /**
58  * ImageReader object for GIF image type.
59  * @author Pankaj Narula
60  */
61 public class GIFReader extends AbstractImageReader {
62     protected static final int GIF_SIG_LENGTH = 10;
63     protected byte[] header;
64
65     public boolean verifySignature(String JavaDoc uri, BufferedInputStream JavaDoc fis)
66             throws IOException JavaDoc {
67         this.imageStream = fis;
68         this.setDefaultHeader();
69         boolean supported = ((header[0] == 'G') && (header[1] == 'I')
70                              && (header[2] == 'F') && (header[3] == '8')
71                              && (header[4] == '7' || header[4] == '9')
72                              && (header[5] == 'a'));
73         if (supported) {
74             setDimension();
75             return true;
76         } else
77             return false;
78     }
79
80     public String JavaDoc getMimeType() {
81         return "image/gif";
82     }
83
84     protected void setDimension() {
85         // little endian notation
86 int byte1 = header[6] & 0xff;
87         int byte2 = header[7] & 0xff;
88         this.width = ((byte2 << 8) | byte1) & 0xffff;
89
90         byte1 = header[8] & 0xff;
91         byte2 = header[9] & 0xff;
92         this.height = ((byte2 << 8) | byte1) & 0xffff;
93     }
94
95     protected void setDefaultHeader() throws IOException JavaDoc {
96         this.header = new byte[GIF_SIG_LENGTH];
97         try {
98             this.imageStream.mark(GIF_SIG_LENGTH + 1);
99             this.imageStream.read(header);
100             this.imageStream.reset();
101         } catch (IOException JavaDoc ex) {
102             try {
103                 this.imageStream.reset();
104             } catch (IOException JavaDoc exbis) {}
105             throw ex;
106         }
107     }
108
109 }
110
111
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