up.java

来自「非常有用的操作pdf文件的java源码」· Java 代码 · 共 101 行

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 * Copyright (c) 2005, www.pdfbox.org
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 *    this list of conditions and the following disclaimer.
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package org.pdfbox.pdmodel.graphics.predictor;

/**
 * The up algorithm.
 * 
 * <code>Up(i,j) = Raw(i,j) - Raw(i,j-1)</code>
 * 
 * <code>Raw(i,j) = Up(i,j) + Raw(i,j-1)</code>
 * 
 * @author [e-mail]
 * @version $Revision: 1.3 $
 */
public class Up extends PredictorAlgorithm 
{
    /**
     * {@inheritDoc}
     */
    public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
            int destDy, int destOffset) 
    {
        int bpl = getWidth()*getBpp();
        // case: y = 0;
        if (srcOffset - srcDy < 0) 
        {
            if (0 < getHeight()) 
            {
                for (int x = 0; x < bpl; x++) 
                {
                    dest[destOffset + x] = src[srcOffset + x];
                }
            }
        } 
        else 
        {
            for (int x = 0; x < bpl; x++) 
            {
                dest[destOffset + x] = (byte) (src[srcOffset + x] - src[srcOffset
                        + x - srcDy]);
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
            int destDy, int destOffset) 
    {
        // case: y = 0;
        int bpl = getWidth()*getBpp();
        if (destOffset - destDy < 0) 
        {
            if (0 < getHeight()) 
            {
                for (int x = 0; x < bpl; x++) 
                {
                    dest[destOffset + x] = src[srcOffset + x];
                }
            }
        } 
        else 
        {
            for (int x = 0; x < bpl; x++) 
            {
                dest[destOffset + x] = (byte) (src[srcOffset + x] + dest[destOffset
                        + x - destDy]);
            }
        }
    }
}