Image rotation is performed by computing the inverse transformation for every destination pixel. Output pixels are computed using bilinear interpolation. RGB images are computed by evaluating one color plane at a time. Image Rotation is a feature that allows the camera to be turned upside down and yet still record a video that is correctly oriented right side up. The dash cameras are mounted or affixed to a vehicle's windshield. The reason for that is you get a better video when the camera is attached to the windshield.
If a camera has the Image Rotation setting then it can actually be mounted upside down on a "smooth, flat, solid surface". It is apparent that if you want to take advantage of this feature then there must be a little creativity on the part of a car dash camera
owner to accomplish this. Why is the feature offered? Seriously there may be some vehicles that it is best suited to mount the camera upside down on the dashboard. One thing to keep in mind is that the mounts are made to be attached to a windshield and using them as a stand instead of as a type of hanger might weaken the mount. Another thing is that the image quality or resolution may be lower when turned upside down. Image rotation is offered on some of the car cameras.