A priori knowledge free piecewise linear two-dimensional warping

Piecewise linear two-dimensional warping (PL2DW) is a practical elastic image matching technique where the pixel-to-pixel correspondence function between a pair of image patterns is defined as a piecewise linear 2D-2D mapping. For accurate matching, the boundary points of linearization, called "pivots", should be placed at the bending and stretching points of image patterns. In conventional PL2DW, it is assumed that the pivots are properly placed by users before their mapping is optimized. This assumption, however, is acceptable only when the a priori knowledge about the deformation characteristics of the image patterns is available. In this paper, an improved PL2DW technique is proposed. In this technique, along with the mapping of pivots, their placement is simultaneously optimized. As a result, pivots are placed automatically at the bending and stretching points of the target and therefore accurate matching is obtained without any a priori knowledge.