Page Orientation
The WIA minidriver must ensure that the WIA_IPS_ORIENTATION property agrees with the current selection area. If an application changes the value of WIA_IPS_ORIENTATION to one that is invalid for the currently selected page size, the minidriver should change the value of WIA_IPS_PAGE_SIZE to a page size that the new orientation value supports.
Note that if WIA_IPS_ORIENTATION is set to LANSCAPE, the extent settings will be "flipped." For example, if an application sets WIA_IPS_PAGE_SIZE to WIA_PAGE_A4, the minidriver should set WIA_IPS_PAGE_WIDTH to 11692 and WIA_IPS_PAGE_HEIGHT to 8267. (The minidriver should also set WIA_IPS_XEXTENT and WIA_IPS_YEXTENT accordingly.) Note that if WIA_IPS_PAGE_SIZE is set to WIA_PAGE_CUSTOM, the orientation setting is not used to determine the extent dimensions of the page to be scanned.