Precision feature point tracking method using a drift-correcting template update strategy

We present a drift-correcting template update strategy for precisely tracking a feature point in 2D image sequences in this paper. The proposed strategy greatly extends Matthews et al’s template tracking strategy [I. Matthews, T. Ishikawa and S. Baker, The template update problem, IEEE Trans. PAMI 26 (2004) 810-815.] by incorporating a robust non-rigid image registration step used in medical imaging. Matthews et al’s strategy uses the first template to correct drifts in the current template; however, the drift would still build up if the first template becomes quite different from the current one as the tracking continues. In our strategy the first template is updated timely when it is quite different from the current one, and henceforth the updated first template can be used to correct template drifts in subsequent frames. The method based on the proposed strategy yields sub-pixel accuracy tracking results measured by the commercial software REALVIZ® MatchMover® Pro 4.0. Our method runs fast on a desktop PC (3.0 GHz Pentium® IV CPU, 1GB RAM, Windows® XP professional operating system, Microsoft Visual C++ 6.0 ® programming), using about 0.03 seconds on average to track the feature point in a frame (under the assumption of a general affine transformation model, 61×61 pixels in template size) and when required, less than 0.1 seconds to update the first template. We also propose the architecture for implementing our strategy in parallel.