package com.tom_roush.pdfbox.pdmodel.graphics.predictor;
/**
* The sub algorithm.
*
* <code>Sub(i,j) = Raw(i,j) - Raw(i-1,j)</code>
*
* <code>Raw(i,j) = Sub(i,j) + Raw(i-1,j)</code>
*
* @author xylifyx@yahoo.co.uk
* @version $Revision: 1.3 $
*/
public class Sub extends PredictorAlgorithm
{
/**
* {@inheritDoc}
*/
public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
int destDy, int destOffset)
{
int bpl = getWidth()*getBpp();
int bpp = getBpp();
// case: x < bpp
for (int x = 0; x < bpl && x < bpp; x++)
{
dest[x + destOffset] = src[x + srcOffset];
}
// otherwise
for (int x = getBpp(); x < bpl; x++)
{
dest[x + destOffset] = (byte) (src[x + srcOffset] - src[x
+ srcOffset - bpp]);
}
}
/**
* {@inheritDoc}
*/
public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
int destDy, int destOffset)
{
int bpl = getWidth()*getBpp();
int bpp = getBpp();
// case: x < bpp
for (int x = 0; x < bpl && x < bpp; x++)
{
dest[x + destOffset] = src[x + srcOffset];
}
// otherwise
for (int x = getBpp(); x < bpl; x++)
{
dest[x + destOffset] = (byte) (src[x + srcOffset] + dest[x
+ destOffset - bpp]);
}
}
}