1. A method of analysis, comprising: registering a target image to define a plurality of keypoints arranged in sets corresponding to polygons or linear segments in the target image, said registering comprising ordering keypoints of at least one set so as to reduce an overall number of said sets; accessing a database of registered and annotated images, and employing a polygon-wise comparison between the target image and each database image; and using said comparison for projecting annotated locations from said database images into the target image.