Helper functions for converting a DataURL to an image and saving to a file

dataurl.clj

(defn dataurl->mime-type
  "Extract the mime-type from a data URL."
  [dataurl]
  (->> (str/split dataurl #",")
       (first)
       (re-find #":(.*?);")
       (second)))

(defn dataurl->image
  "Extract the image data from a data URL."
  [dataurl]
  (let [data-str (second (str/split dataurl #","))
        bytes    (DatatypeConverter/parseBase64Binary data-str)]
    (ImageIO/read (ByteArrayInputStream. bytes))))

;; Example - save image as file
(let [mime-type (dataurl->mime-type dataurl)
      format    (second (str/split mime-type #"/"))
      image     (dataurl->image dataurl)
      out       (File. (str "img." format))]
  (ImageIO/write ^BufferedImage image ^String format out))