1. A method performed by an image capture device, the method comprising: comparing a calibration image of at least a portion of a background surface having a substantially uniform grey color that is approximately 50% grey to a previous image of the portion of the background surface, the calibration image and the previous image captured by a photosensor array of the image capture device; compensating for at least one of a photo response non-uniformity or a dark signal non-uniformity of one or more pixels of the photosensor array based on comparing the calibration image to the previous image; and subsequent to the compensating, capturing a scanned image of a medium and the portion of the background surface using light received by the photosensor array from the medium and the portion of the background surface.