/*
* 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.
*/
package org.apache.pdfbox.filter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Iterator;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pdfbox.cos.COSArray;
import org.apache.pdfbox.cos.COSBase;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
/**
* A filter for stream data.
*
* @author Ben Litchfield
* @author John Hewson
*/
public abstract class Filter
{
private static final Log log = LogFactory.getLog(Filter.class);
protected Filter()
{
}
/**
* Decodes data, producing the original non-encoded data.
* @param encoded the encoded byte stream
* @param decoded the stream where decoded data will be written
* @param parameters the parameters used for decoding
* @param index the index to the filter being decoded
* @return repaired parameters dictionary, or the original parameters dictionary
* @throws IOException if the stream cannot be decoded
*/
public abstract DecodeResult decode(InputStream encoded, OutputStream decoded, COSDictionary parameters,
int index) throws IOException;
/**
* Encodes data.
* @param input the byte stream to encode
* @param encoded the stream where encoded data will be written
* @param parameters the parameters used for encoding
* @param index the index to the filter being encoded
* @throws IOException if the stream cannot be encoded
*/
public final void encode(InputStream input, OutputStream encoded, COSDictionary parameters,
int index) throws IOException
{
encode(input, encoded, parameters.asUnmodifiableDictionary());
}
// implemented in subclasses
protected abstract void encode(InputStream input, OutputStream encoded,
COSDictionary parameters) throws IOException;
// gets the decode params for a specific filter index, this is used to
// normalise the DecodeParams entry so that it is always a dictionary
protected COSDictionary getDecodeParams(COSDictionary dictionary, int index)
{
COSBase obj = dictionary.getDictionaryObject(COSName.DECODE_PARMS, COSName.DP);
if (obj instanceof COSDictionary)
{
return (COSDictionary)obj;
}
else if (obj instanceof COSArray)
{
COSArray array = (COSArray)obj;
if (index < array.size())
{
return (COSDictionary)array.getObject(index);
}
}
else if (obj != null)
{
log.error("Expected DecodeParams to be an Array or Dictionary but found " +
obj.getClass().getName());
}
return new COSDictionary();
}
/**
* Finds a suitable image reader for a format.
*
* @param formatName The format to search for.
* @param errorCause The probably cause if something goes wrong.
* @return The image reader for the format.
* @throws MissingImageReaderException if no image reader is found.
*/
protected ImageReader findImageReader(String formatName, String errorCause) throws MissingImageReaderException
{
Iterator<ImageReader> readers = ImageIO.getImageReadersByFormatName(formatName);
ImageReader reader = null;
while (readers.hasNext())
{
reader = readers.next();
if (reader.canReadRaster())
{
break;
}
}
if (reader == null)
{
throw new MissingImageReaderException("Cannot read " + formatName + " image: " + errorCause);
}
return reader;
}
}