ui/src/main/resources/jcr_root/libs/sling/commons/thumbnails/transformers/scale/edit.json

 {
    "jcr:primaryType": "nt:unstructured",
    "sling:resourceType": "sling-cms/components/editor/slingform",
    "button": "Save",
    "fields": {
        "jcr:primaryType": "nt:unstructured",
        "sling:resourceType": "sling-cms/components/general/container",
        "both": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/select",
            "label": "Both Width and Height",
            "name": "both",
            "type": "text"
        },
        "width": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/text",
            "label": "Width",
            "name": "width",
            "type": "text"
        },
        "height": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/text",
            "label": "Height",
            "name": "height",
            "type": "text"
        }
    }
}