captcha.pt

<span tal:define="name name|field.name;
        css_class css_class|field.widget.css_class;
        oid oid|field.oid;
        captcha captcha|field.widget.captcha;
        style style|field.widget.style;
        "
         tal:omit-tag="">
    <input type="text" name="${name}" value="${cstruct}"
             tal:attributes="class string: form-control ${css_class or ''};
            style style;
            attributes|field.widget.attributes|{};"
           id="${oid}"/>
    <script type="text/javascript">
      deform.addCallback(
              '${oid}',
              function (oid) {
                  $("#" + oid).parent().prepend('<img style="height:30px; width:auto; margin-bottom:5px;' +
                          '" src="${home}/captcha/${captcha}.png">')

                  $('#'+oid).on('input', function (evt) {
                      $(this).val(function (_, val) {
                          return val.toUpperCase();
                      });
                  });
              });
    </script>
</span>