Nonlinear Nonlocal Prior Term

To deal with the narrower secondary roads, we construct a nonlinear nonlocal prior energy. It contains a second order polynomial expansion of the inner product of the normal vectors of two pixels. When a pair of interacting pixels is on the same side of a network branch (in our case, a road), it reinforces the effect of the generic prior term in [1], and when a pair of interacting pixels is on opposite sides of a network branch, it partly annuls the effect of the generic prior term [1]. Accordingly, the interaction between pairs of pixels on the same side of a network branch is stronger than that between pairs of pixels on opposite sides of a network branch.

Fig. 5 presents results obtained with the nonlinear nonlocal prior term, at reduced resolutions. The first column shows the input image data, which is either at 1/4 or 1/2 resolution. The two columns on the right show the corresponding results obtained with and without the nonlinear nonlocal prior term. The importance of this new term is clear: it facilitates greatly the retrieval of secondary roads.

Picture 10

Fig. 5 Experiments at reduced resolutions. First column: input images. Two rightmost columns: corresponding results obtained with and without the nonlinear nonlocal prior term.



Last update: Dec. 10, 2008