/*
* $Id: Predictor.java,v 1.3 2010-05-23 22:07:04 lujke Exp $
*
* Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
* Santa Clara, California 95054, U.S.A. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package com.sun.pdfview.decode;
import java.nio.ByteBuffer;
import java.io.IOException;
import com.sun.pdfview.PDFObject;
import com.sun.pdfview.PDFParseException;
/**
* The abstract superclass of various predictor objects that undo well-known
* prediction algorithms.
*/
public abstract class Predictor {
/** well known algorithms */
public static final int TIFF = 0;
public static final int PNG = 1;
/** the algorithm to use */
private int algorithm;
/** the number of colors per sample */
private int colors = 1;
/** the number of bits per color component */
private int bpc = 8;
/** the number of columns per row */
private int columns = 1;
/**
* Create an instance of a predictor. Use <code>getPredictor()</code>
* instead of this.
*/
protected Predictor(int algorithm) {
this.algorithm = algorithm;
}
/**
* Actually perform this algorithm on decoded image data.
* Subclasses must implement this method
*/
public abstract ByteBuffer unpredict(ByteBuffer imageData)
throws IOException;
/**
* Get an instance of a predictor
*
* @param params the filter parameters
*/
public static Predictor getPredictor(PDFObject params)
throws IOException
{
// get the algorithm (required)
PDFObject algorithmObj = params.getDictRef("Predictor");
if (algorithmObj == null) {
// no predictor
return null;
}
int algorithm = algorithmObj.getIntValue();
// create the predictor object
Predictor predictor = null;
switch (algorithm) {
case 1:
// no predictor
return null;
case 2:
predictor = new TIFFPredictor();
break;
case 10:
case 11:
case 12:
case 13:
case 14:
case 15:
predictor = new PNGPredictor();
break;
default:
throw new PDFParseException("Unknown predictor: " + algorithm);
}
// read the colors (optional)
PDFObject colorsObj = params.getDictRef("Colors");
if (colorsObj != null) {
predictor.setColors(colorsObj.getIntValue());
}
// read the bits per component (optional)
PDFObject bpcObj = params.getDictRef("BitsPerComponent");
if (bpcObj != null) {
predictor.setBitsPerComponent(bpcObj.getIntValue());
}
// read the columns (optional)
PDFObject columnsObj = params.getDictRef("Columns");
if (columnsObj != null) {
predictor.setColumns(columnsObj.getIntValue());
}
// all set
return predictor;
}
/**
* Get the algorithm in use
*
* @return one of the known algorithm types
*/
public int getAlgorithm() {
return algorithm;
}
/**
* Get the number of colors per sample
*/
public int getColors() {
return colors;
}
/**
* Set the number of colors per sample
*/
protected void setColors(int colors) {
this.colors = colors;
}
/**
* Get the number of bits per color component
*/
public int getBitsPerComponent() {
return bpc;
}
/**
* Set the number of bits per color component
*/
public void setBitsPerComponent(int bpc) {
this.bpc = bpc;
}
/**
* Get the number of columns
*/
public int getColumns() {
return columns;
}
/**
* Set the number of columns
*/
public void setColumns(int columns) {
this.columns = columns;
}
}