1. A method for automatically determining pose of a shape undergoing a combination of affine deformation and non-linear deformation with a vision system comprising the steps of: acquiring an image, with an image sensor, of an object containing the shape; performing a coarse location of the shape to identify and select at least one shape candidate matching a predetermined shape; refining the affine parameters and non-linear distortion parameters for the best matching candidate shape; and generating a shape representation of at least one refined best matching candidate shape, wherein the non-linear deformation is defined by at least one of stroke width and spline warp.