1. Within an image acquisition device, a method of detecting rotation from matching corner regions of acquired images, comprising: acquiring a sequence of image frames; and determining a measure of frame-to-frame rotation, including: performing a global XY alignment of a first frame and a second, following frame of said sequence of image frames; determining local XY alignments in at least two matching corner regions of the first and second frames after the global XY alignment; and based on the differences between said local XY alignments, determining a global rotation of the second frame relative to the first frame; and performing a further action based on the determined global rotation.