return null;
}
protected byte[] unfilterScanline(final FilterType filterType, final byte[] src, final byte[] prev,
final int bytesPerPixel) throws ImageReadException, IOException {
final ScanlineFilter filter = getScanlineFilter(filterType, bytesPerPixel);
final byte[] dst = new byte[src.length];
filter.unfilter(src, dst, prev);
return dst;
}