@Override
public void addElement(int index, TIFFImageReader reader, ImageReaderSource<?> source) throws IOException {
final RasterSlice slice = new RasterSlice();
slice.source=source;
// get metadata and check if this is an overview or not
final TIFFImageMetadata metadata = (TIFFImageMetadata) reader.getImageMetadata(index);
final TIFFIFD IFD = metadata.getRootIFD();