ing the result into the imgdata.thumbnail.thumb buffer.</p>
    <p>unpack_thumb_ex(int i): reads i-th thumbnail (thumbnails list is
      available in imgdata.thumbs_list structure).</p>
    <p> JPEG previews are placed into this buffer without any changes (with the
      header etc.). Other preview formats are placed into the buffer in the form
      of the unpacked bitmap image (three components, 8 bits per component).<br>
      The thumbnail format is written to the imgdata.thumbnail.tformat field;
     