Filters Limit the File Types That the User Can Select

- (IBAction)askUserForImage:(id)sender {
   NSOpenPanel*    panel = [NSOpenPanel openPanel];
   // Let the user select any images supported by
   // the NSImage class.
   NSArray* imageTypes = [NSImage imageTypes];
   [panel setAllowedFileTypes:imageTypes];
   [panel beginWithCompletionHandler:^(NSInteger result){
      if (result == NSFileHandlingPanelOKButton) {
         // Open the image.
      }
}]; }