private static String bitmapToString(Bitmap bitmap) {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
  byte[] b = baos.toByteArray();
  return Base64.encodeToString(b, Base64.DEFAULT);
}

private static Bitmap stringToBitmap(String encodedString) {
  try {
    byte[] encodeByte = Base64.decode(encodedString, Base64.DEFAULT);
    return BitmapFactory.decodeByteArray(encodeByte, 0, encodeByte.length);
  } catch (Exception e) {
    e.getMessage();
    return null;
  }
}