... Moving the sample locations to achieve the desired warping will result in an irregularly sampled image plane. These irregularly spaced samples will then be brought back to regularly spaced positions, hence warping the image. ... The sampled impulse response, , is a function of the sample positions, . ... Allowing the sum to go outside the image boundaries ( or ) includes some ``anchor'' samples outside the image, which tends to stabilize the solution trajectory when is minimized. ...