1. An imaging system for sensing an object, said imaging system comprising: (a) an image sensor comprising an array of photo-receptive sites; (b) a backing having a surface opposed to said sensor; and (c) an image processor having a plurality of stat buffers and that analyzes candidate edges for bounding regions and identifies shadows cast by an object adjacent said backing as edges of a bounding region based, at least in part, on: (i) a variable luminance threshold value automatically calculated using a maximum instance of a plurality of statistical values measured over at least one of a column or row of said array, where said variable luminance threshold value causes detection of shadows cast by said object on said backing; and (ii) the presence of detected said shadows in a contiguous plurality of stat buffers.