Use directory as label field

metadata.json

{
  "name": "path-to-label",
  "kind": "script",
  "description": "Extracts the last component of paths as the label",
  "source_code": "script.whizzml",
  "imports":[
    ],
  "inputs":[
    {
      "name": "source",
      "type": "source-id",
      "default": "",
      "description": "The composite image source, or empty to use dataset"
    },
    {
      "name": "dataset",
      "type": "dataset-id",
      "default": "",
      "description": "The images dataset, or empty to use source"
    },
    {
      "name": "path-field",
      "type": "string",
      "default": "filename",
      "description": "Name of the field containing image paths"
    }
  ],
  "outputs":[
    {
      "name": "result",
      "type": "dataset-id",
      "description": "The resulting labeled dataset"
    }]
}

script.whizzml

(define (flatexp field-name)
  (flatline "(replace (f {{field-name}}) \"([^/]+/)*([^/]+)/[^/]+\" \"$2\")"))

(define (add-label dataset field-name)
  (log-info "Adding label using field " field-name "...")
  (wait (create-dataset dataset
                        {"new_fields" [{"name" "label"
                                        "field" (flatexp field-name)}]
                         "refresh_objective" true})))

(define (do-it source-id path-name)
  (log-info "Closing input source...")
  (wait (update source-id {"closed" true}))
  (log-info "Creating dataset...")
  (let (ds (wait (create-dataset source-id))
        res (wait (add-label ds path-name)))
    (delete ds)
    res))

(define result
  (if (empty? source)
    (add-label dataset path-field)
    (do-it source path-field)))