Disclosed is method of measuring the displacement between a reference region of a reference image and a sample region of a sample image. The method spatially varies the reference region using a one-dimensional filter having complex kernel values, wherein a length (radius) and direction (angle or tangent segment) of the filter is a function of position in the reference region. The method then measures a displacement between the reference region and the sample region by comparing the spatially varied reference region and the sample region.