restrict the upload of files other than images in the upload field of the vendor

hi, when trying to upload file in this case:

case ‘upload’:
$ WCFM-> wcfm_fields-> wcfm_generate_form_field (array ($ field_id => array (‘label’ => __ ($ wcfmvm_registration_custom_field [‘label’], ‘WCfM’), ‘custom_attributes’ => $ custom_attributes, ‘type’ => ‘file’, ‘class’ => ‘wcfm_ele’, ‘label_class’ => ‘wcfm_title’, ‘hints’ => __ ($ wcfmvm_registration_custom_field [‘help_text’], ‘WCfM’))));
break;

All files are allowed by default but I only need a png or jpg image to be loaded, nothing else. I tried some things but I couldn’t get it to work, can you please tell me what to add there?