Patent ID: 9367928
Filing Date: 2016-06-14
CPC Classification: G06K,G06T

Claim Text:
1. A method for matching point regions in images with radial distortion that, given two frames acquired by a camera with radial distortion, it estimates a global image distortion and local transformations undergone by the image regions between frames, the method comprising: i. receiving a plurality of frames acquired from the camera with radial distortion; ii. selecting , using a processor, set of image regions N iii. selecting at least one motion model w with a vector of parameters p that describes one or more local deformations undergone by a plurality of generic image regions N in the case of the camera being a perspective camera with no lens distortion; iv. performing a 2-dimensional mapping function f , using the processor, for modelling the camera radial distortion such that a relation between a plurality of distorted image points x and a plurality of undistorted image points u, both expressed in a coordinate system with origin in the image center O, is given by u=f (x;ξ) with f defined as: where ξ, represents an image distortion parameter that quantifies the effect of a lens radial distortion in pixel units; v. deriving a warping model v where q=( p ξ ) is the vector of the warp parameters, f 1 denotes the inverse of the 2-dimensional mapping function f, w is the motion model, and g e is an approximation of the mapping function f with formula: with c being the coordinates of a center of a considered image region of the set of image regions; vi. deriving a cost function that provides a cumulative alignment error ε in aligning the K image regions in the current frame T, with the putative corresponding regions in a following frame I, and that has the form: where q i is with p i being a vector of parameters of the motion model w for the case of a particular image region N i , and ξ being the global image distortion parameter; vii. estimating jointly, using the processor, the local motion parameters p viii. updating, using the processor, a position and appearance of the set of image regions N