Figure 4

Example of image alignment. Image (a) and (b) correspond to times k - 1 and k, respectively, of the video sequence; (c) is the image at k - 1 warped with ${\widehat{H}}^k$; (d) is the difference between aligned images, i.e., (b) and (c); and (e) is the corresponding image of differences in the rectified domain. Both (d) and (e) have been binarized for better visualization: white regions correspond to regions of difference, which usually correspond to the lower edge of vehicles.