It was taken through a “fisheye” wide-angle lens on the left “eye” of a stereo pair of Hazard-Avoidance cameras on the left-rear side of the rover. The image is one-half of full resolution. The clear dust cover that protected the camera during landing has been sprung open. Part of the spring that released the dust cover can be seen at the bottom right, near the rover’s wheel.
The rover also “posted” this photo to Facebook:
Eye in the Sky: MRO’s HiRISE camera caught this shot of me & my parachute during landing at Mars #MSL