How to computer isometric tiledmap ContentSize()? mean(width & height)?

cocos2d-x
#1

I know if a tiledmap is TMXOrientationOrtho, then directly call tiledmap.getContentSize() can get answer, but if tiledmap is a TMXOrientationIso or TMXOrientationHex , then should be different, because of 45 degree problem. can somebody know it? thanks.