ui/src/main/resources/jcr_root/libs/sling/commons/thumbnails/transformers/resize/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",
        "width": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/text",
            "label": "Width",
            "name": "width",
            "type": "number"
        },
        "height": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/text",
            "label": "Height",
            "name": "height",
            "type": "number"
        },
        "keepAspectRatio": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/select",
            "label": "Keep Aspect Ratio",
            "name": "keepAspectRatio",
            "options": {
                "yes": {
                    "label": "Yes",
                    "value": true
                },
                "no": {
                    "label": "No",
                    "value": false
                }
            }
        },
        "keepAspectRatioTypeHint": {
            "jcr:primaryType": "nt:unstructured",
            "sling:resourceType": "sling-cms/components/editor/fields/hidden",
            "name": "keepAspectRatio@TypeHint",
            "value": "Boolean"
        }
    }
}