code: public InputStream unwrapInputStream(InputStream is) throws IOException {
      if (imageCodec != null) {
        return imageCodec.createInputStream(is);
      } else {
        return is;
      }
    }
docs: Unwrap a compressed input stream by wrapping it with a decompressor based
  on this codec. If this instance represents no compression, simply return
  the input stream.
  @return a stream that provides uncompressed data
  @throws IOException If the decompressor cannot be instantiated or an IO
  error occurs.