mkmapview - 将 CGPoint 转换为经纬度

Question

我有一个 CGPoint，我需要将其转换为 lat long。

CGPoint centerOfMap = CGPointMake(mapView.frame.size.width/2,mapView.frame.size.heigh/2);
CGPoint topMidOfMap = CGPointMake(centerOfMap.x, centerOfMap.y-200); //Step 1
//Now get difference of longitude and latitude
CLLocationCoordinate2D centerOfMapCoord = [mapView convertPoint:centerOfMap toCoordinateFromView:mapView];   //Step 2
CLLocationCoordinate2D topMidOfMapCoord = [mapView convertPoint:topMidOfMap toCoordinateFromView:mapView];   //Step 2

我无法获得 CGPoint 的准确纬度。任何指针？