private void UnfilterRowSub(int nbytes)
{
int i, j;
for (i = 1; i <= ImgInfo.BytesPixel; i++) {
rowb[i] = (byte)(rowbfilter[i]);
}
for (j = 1, i = ImgInfo.BytesPixel + 1; i <= nbytes; i++, j++) {
rowb[i] = (byte)(rowbfilter[i] + rowb[j]);
}
}