15 September 2016
Sorry, for misunderstanding. I've just checked the ImageDocument::ImageRotation description in the Developer's Help.
The ImageDocument::ImageRotation property shows the changes in orientation only if you make such changes after opening or after SaveModified method. Example: if you call ImageDocument::Transform( RT Clockwise, ... ) then you will get ImageDocument::ImageRotation = RT_Clockwise value. So, ImageDocument::ImageRotation is not about source image rotation. It is about image modification which you implement with ImageDocument after opening.
In order to get the current image orientation you should call FRPage::DetectOrientation method and look in the TextOrientation::RotationType property. For more details, find FRPage::DetectOrientation method in Developer's Help.
Hope, it will help!