org.apache.xmlgraphics.image.loader.impl.JPEGFile Maven / Gradle / Ivy
/*
* 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: JPEGFile.java 1681108 2015-05-22 13:26:12Z ssteiner $ */
package org.apache.xmlgraphics.image.loader.impl;
import java.io.DataInput;
import java.io.IOException;
import java.io.InputStream;
import javax.imageio.stream.ImageInputStream;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Provides methods useful for processing JPEG files.
*/
public class JPEGFile implements JPEGConstants {
/** logger */
protected static final Log log = LogFactory.getLog(JPEGFile.class);
private DataInput in;
/**
* Constructor for ImageInputStreams.
* @param in the input stream to read the image from
*/
public JPEGFile(ImageInputStream in) {
this.in = in;
}
/**
* Constructor for InputStreams.
* @param in the input stream to read the image from
*/
public JPEGFile(InputStream in) {
this.in = new java.io.DataInputStream(in);
}
/**
* Returns the {@link DataInput} instance this object operates on.
* @return the data input instance
*/
public DataInput getDataInput() {
return this.in;
}
/**
* Reads the next marker segment identifier and returns it.
* @return the marker segment identifier
* @throws IOException if an I/O error occurs while reading from the image file
*/
public int readMarkerSegment() throws IOException {
int marker;
do {
marker = in.readByte() & 0xFF;
//Skip any non-0xFF bytes (useful for JPEG files with bad record lengths)
} while (marker != MARK);
int segID;
do {
segID = in.readByte() & 0xFF;
//Skip any pad bytes (0xFF) which are legal here.
} while (segID == 0xFF);
return segID;
}
/**
* Reads the segment length of the current marker segment and returns it.
* The method assumes the file cursor is right after the segment header.
* @return the segment length
* @throws IOException if an I/O error occurs while reading from the image file
*/
public int readSegmentLength() throws IOException {
int reclen = in.readUnsignedShort();
return reclen;
}
/**
* Skips the current marker segment.
* The method assumes the file cursor is right after the segment header.
* @throws IOException if an I/O error occurs while reading from the image file
*/
public void skipCurrentMarkerSegment() throws IOException {
int reclen = readSegmentLength();
in.skipBytes(reclen - 2);
}
}