@Override public String getId() {
    return "MaskTransformation(maskId=" + mContext.getResources().getResourceEntryName(mMaskId)
        + ")";
  }
@param maskId If you change the mask file, please also rename the mask file, or Glide will get
the cache with the old mask. Because getId() return the same values if using the
same make file name. If you have a good idea please tell us, thanks.
core/src/main/java/jp/wasabeef/glide/transformations/MaskTransformation.java