package com.tom_roush.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 xylifyx@yahoo.co.uk
* @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]);
}
}
}
}