package com.tom_roush.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: 1.3 $
*/
public class Average extends PredictorAlgorithm
{
/**
* Not an optimal version, but close to the def.
*
* {@inheritDoc}
*/
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));
}
}
/**
* {@inheritDoc}
*/
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));
}
}
}