/**
  * Validate the form
  *
  * @return  void
  */
 private function validateForm()
 {
     // is the form submitted?
     if ($this->frm->isSubmitted()) {
         // cleanup the submitted fields, ignore fields that were added by hackers
         $this->frm->cleanupFields();
         // validate all images
         for ($i = 0; $i < $this->imageUploadFields; $i++) {
             // validate fields
             if ($this->frm->getField('image' . $i)->isFilled()) {
                 // correct extension
                 if ($this->frm->getField('image' . $i)->isAllowedExtension(array('jpg', 'jpeg', 'gif', 'png'), BL::err('JPGGIFAndPNGOnly'))) {
                     // correct mimetype?
                     $this->frm->getField('image' . $i)->isAllowedMimeType(array('image/gif', 'image/jpg', 'image/jpeg', 'image/png'), BL::err('JPGGIFAndPNGOnly'));
                 }
             }
         }
         // no errors?
         if ($this->frm->isCorrect()) {
             // build item
             $item['language'] = $this->record['language'];
             $item['gallery_id'] = $this->id;
             for ($i = 0; $i < $this->imageUploadFields; $i++) {
                 if ($this->frm->getField('image' . $i)->isFilled()) {
                     // get the sequence everytime
                     $item['sequence'] = BackendSlideshowModel::getMaximumImageSequence($this->id) + 1;
                     // create new filename
                     $filename = time() . $i . "." . $this->frm->getField('image' . $i)->getExtension();
                     // add filename to item
                     $item['filename'] = $filename;
                     // If height is not set, scale the image proportionally to the given width
                     if ($this->record['height'] != 0) {
                         // upload image width gallery dimensions
                         $this->frm->getField('image' . $i)->createThumbnail(FRONTEND_FILES_PATH . '/slideshow/' . $filename, $this->record['width'], $this->record['height'], true, false, 100);
                     } else {
                         $this->frm->getField('image' . $i)->createThumbnail(FRONTEND_FILES_PATH . '/slideshow/' . $filename, $this->record['width'], null, true, true, 100);
                     }
                     // create thumbnail for later use
                     $this->frm->getField('image' . $i)->createThumbnail(FRONTEND_FILES_PATH . '/slideshow/thumbnails/' . $filename, 100, 100, false, false, 100);
                     // insert image values in database
                     BackendSlideshowModel::insertImage($item);
                 }
             }
             // trigger event
             BackendModel::triggerEvent($this->getModule(), 'after_edit', array('item' => $item));
             // everything is saved, so redirect to the overview
             $this->redirect(BackendModel::createURLForAction('Edit') . '&report=saved&var=' . '&id=' . $this->id . '#images');
         }
     }
 }