/*
* 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: PreloaderGIF.java 606580 2007-12-23 17:45:02Z jeremias $ */
package org.apache.xmlgraphics.image.loader.impl;
import java.io.IOException;
import javax.imageio.stream.ImageInputStream;
import javax.xml.transform.Source;
import org.apache.xmlgraphics.image.loader.ImageContext;
import org.apache.xmlgraphics.image.loader.ImageInfo;
import org.apache.xmlgraphics.image.loader.ImageSize;
import org.apache.xmlgraphics.image.loader.util.ImageUtil;
import org.apache.xmlgraphics.util.MimeConstants;
/**
* Image preloader for GIF images.
*/
public class PreloaderGIF extends AbstractImagePreloader {
private static final int GIF_SIG_LENGTH = 10;
/** {@inheritDoc} */
public ImageInfo preloadImage(String uri, Source src, ImageContext context)
throws IOException {
if (!ImageUtil.hasImageInputStream(src)) {
return null;
}
ImageInputStream in = ImageUtil.needImageInputStream(src);
byte[] header = getHeader(in, GIF_SIG_LENGTH);
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) {
ImageInfo info = new ImageInfo(uri, MimeConstants.MIME_GIF);
info.setSize(determineSize(header, context));
return info;
} else {
return null;
}
}
private ImageSize determineSize(byte[] header, ImageContext context) {
// little endian notation
int byte1 = header[6] & 0xff;
int byte2 = header[7] & 0xff;
int width = ((byte2 << 8) | byte1) & 0xffff;
byte1 = header[8] & 0xff;
byte2 = header[9] & 0xff;
int height = ((byte2 << 8) | byte1) & 0xffff;
ImageSize size = new ImageSize(width, height, context.getSourceResolution());
size.calcSizeFromPixels();
return size;
}
}