function getImageFromLocalURL(urlString) {
  // read image content from file
  let fileManager = NSFileManager.defaultManager()
  if (fileManager.fileExistsAtPath(urlString)) {
    return NSImage.alloc().initWithContentsOfFile(urlString)
  }
}
Loads the image from the specified local URL and creates an NSImage instance.

@param {String} urlString
@returns {NSImage}