/*
* 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: PreloaderJPEG.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.ImageException;
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 JPEG images.
*/
public class PreloaderJPEG extends AbstractImagePreloader implements JPEGConstants {
private static final int JPG_SIG_LENGTH = 3;
/** {@inheritDoc}
* @throws ImageException */
public ImageInfo preloadImage(String uri, Source src, ImageContext context)
throws IOException, ImageException {
if (!ImageUtil.hasImageInputStream(src)) {
return null;
}
ImageInputStream in = ImageUtil.needImageInputStream(src);
byte[] header = getHeader(in, JPG_SIG_LENGTH);
boolean supported = ((header[0] == (byte)MARK)
&& (header[1] == (byte)SOI)
&& (header[2] == (byte)MARK));
if (supported) {
ImageInfo info = new ImageInfo(uri, MimeConstants.MIME_JPEG);
info.setSize(determineSize(in, context));
return info;
} else {
return null;
}
}
private ImageSize determineSize(ImageInputStream in, ImageContext context)
throws IOException, ImageException {
in.mark();
try {
ImageSize size = new ImageSize();
//TODO Read resolution from EXIF if there's no APP0
//(for example with JPEGs from digicams)
while (true) {
int segID = readMarkerSegment(in);
//System.out.println("Segment: " + Integer.toHexString(segID));
switch (segID) {
case SOI:
case NULL:
break;
case APP0:
int reclen = in.readUnsignedShort();
in.skipBytes(7);
int densityUnits = in.read();
int xdensity = in.readUnsignedShort();
int ydensity = in.readUnsignedShort();
if (densityUnits == 2) {
//dots per centimeter
size.setResolution(xdensity * 28.3464567 / 72, ydensity * 28.3464567 / 72);
//TODO Why is 28.3464567 used for cm to inch conversion?
//We normally use 25.4.
} else if (densityUnits == 1) {
//dots per inch
size.setResolution(xdensity, ydensity);
} else {
//resolution not specified
size.setResolution(context.getSourceResolution());
}
if (size.getWidthPx() != 0) {
size.calcSizeFromPixels();
return size;
}
in.skipBytes(reclen - 14);
break;
case SOF0:
case SOF1:
case SOF2: // SOF2 and SOFA are only supported by PDF 1.3
case SOFA:
in.skipBytes(2); //length field
in.skipBytes(1);
int height = in.readUnsignedShort();
int width = in.readUnsignedShort();
size.setSizeInPixels(width, height);
if (size.getDpiHorizontal() != 0) {
size.calcSizeFromPixels();
return size;
}
break;
case SOS:
case EOI:
if (size.getDpiHorizontal() == 0) {
size.setResolution(context.getSourceResolution());
size.calcSizeFromPixels();
}
return size;
default:
reclen = in.readUnsignedShort();
in.skipBytes(reclen - 2);
}
}
} finally {
in.reset();
}
}
private int readMarkerSegment(ImageInputStream in) throws IOException {
int marker;
do {
marker = in.read();
} while (marker != MARK);
int segID = in.read();
return segID;
}
}