Subpixel accuracy image registration with application to unsteadiness correction

Image registration refers to the problem of spatially aligning the images in an image sequence. The proposed efficient search method estimates the subpixel displacements causing the misregistration of two frames faster than other methods without any loss in accuuracy. It is assumed that the misregistration is due to global motion. The criterion function used is the mean-squared error over the displaced frames in which image intensities at subpixel locations are evaluated using bilinear interpolation only once in the formula. A novel nearclosed-form solution does not use any search unless absolutely necessary. An extension of the near-closed-form solution that is insensitive to intensity variations between the frames can account for contrast and brightness changes in a sequence. Simulations on unsteady image sequences demonstrate the superiority of the proposed near closed-form solution. The application to de-interlacing also gives good results.