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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id$ */
package org.apache.fop.image.analyser;
// Java
import java.io.InputStream;
import java.io.IOException;
// FOP
import org.apache.fop.image.FopImage;
import org.apache.fop.apps.FOUserAgent;
/**
* ImageReader object for GIF image type.
*
* @author Pankaj Narula
* @version $Id$
*/
public class GIFReader implements ImageReader {
private static final int GIF_SIG_LENGTH = 10;
/** @see org.apache.fop.image.analyser.ImageReader */
public FopImage.ImageInfo verifySignature(String uri, InputStream bis,
FOUserAgent ua) throws IOException {
byte[] header = getDefaultHeader(bis);
boolean supported = ((header[0] == 'G')
&& (header[1] == 'I')
&& (header[2] == 'F')
&& (header[3] == '8')
&& (header[4] == '7' || header[4] == '9')
&& (header[5] == 'a'));
if (supported) {
FopImage.ImageInfo info = getDimension(header);
info.originalURI = uri;
info.mimeType = getMimeType();
info.inputStream = bis;
return info;
} else {
return null;
}
}
/**
* Returns the MIME type supported by this implementation.
*
* @return The MIME type
*/
public String getMimeType() {
return "image/gif";
}
private FopImage.ImageInfo getDimension(byte[] header) {
FopImage.ImageInfo info = new FopImage.ImageInfo();
// little endian notation
int byte1 = header[6] & 0xff;
int byte2 = header[7] & 0xff;
info.width = ((byte2 << 8) | byte1) & 0xffff;
byte1 = header[8] & 0xff;
byte2 = header[9] & 0xff;
info.height = ((byte2 << 8) | byte1) & 0xffff;
return info;
}
private byte[] getDefaultHeader(InputStream imageStream)
throws IOException {
byte[] header = new byte[GIF_SIG_LENGTH];
try {
imageStream.mark(GIF_SIG_LENGTH + 1);
imageStream.read(header);
imageStream.reset();
} catch (IOException ex) {
try {
imageStream.reset();
} catch (IOException exbis) {
// throw the original exception, not this one
}
throw ex;
}
return header;
}
}
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