A method for registering images aligns a fixed image with a corresponding moving image. A target image and a reference image are selected. The reference and target images are relatively low-res representations of the fixed and moving images respectively. A current image distortion map is determined that defines distortions between the target and reference images. A residual image is determined by comparing the reference image and a warped target image derived from the target image based on the current image distortion map. A residual image distortion map is determined based on transform coefficients of cosine functions fitted to the residual image. The coefficients are determined by applying a DCT to a signal formed by the residual image and image gradients of the warped target or reference image. The current image distortion map is combined with the residual image distortion map to align the fixed image and the moving image.