/**
 * Copyright (c) 2005, www.pdfbox.org
 * All rights reserved.
 *
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 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
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 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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package org.pdfbox.pdmodel.graphics.predictor;

/**
 * We can use raw on the right hand side of
 * the decoding formula because it is already decoded.
 * 
 * <code>average(i,j) = raw(i,j) + (raw(i-1,j)+raw(i,j-1)/2</code>
 * 
 * decoding
 * 
 * <code>raw(i,j) = avarage(i,j) - (raw(i-1,j)+raw(i,j-1)/2</code>
 * 
 * @author xylifyx@yahoo.co.uk
 * @version $Revision: 1.2 $
 */
public class Average extends PredictorAlgorithm 
{
    /**
     * Not an optimal version, but close to the def.
     * 
     * @see org.pdfbox.pdmodel.graphics.predictor.PredictorAlgorithm#encodeLine(byte[], byte[],
     *      int, int, int, int)
     */
    public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
            int destDy, int destOffset) 
    {
        int bpl = getWidth() * getBpp();
        for (int x = 0; x < bpl; x++) 
        {
            dest[x + destOffset] = (byte) (src[x + srcOffset] - ((leftPixel(
                    src, srcOffset, srcDy, x) + abovePixel(src, srcOffset,
                    srcDy, x)) >>> 2));
        }
    }

    /**
     * @see org.pdfbox.pdmodel.graphics.predictor.PredictorAlgorithm#decodeLine(byte[], byte[],
     *      int, int, int, int)
     */
    public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
            int destDy, int destOffset) 
    {
        int bpl = getWidth() * getBpp();
        for (int x = 0; x < bpl; x++) 
        {
            dest[x + destOffset] = (byte) (src[x + srcOffset] + ((leftPixel(
                    dest, destOffset, destDy, x) + abovePixel(dest,
                    destOffset, destDy, x)) >>> 2));
        }
    }
}