cated structure will contains
      JPEG image (i.e. <strong>type</strong> field is equal to
      LIBRAW_IMAGE_JPEG). For some cameras with RGB-bitmap thumbnail (Kodak
      SLRs) returned structure contains RGB bitmap (<strong>type</strong> field
      is equal to LIBRAW_IMAGE_JPEG, see structure description for details).</p>
    <p>unpack_thumb() should be called before dcraw_make_mem_thumb();</p>
    <p>Returns NULL in case of an error. If caller has passed not-NULL value as
      errorcode parameter, t