Fusion of images on affine sampling grids

We present a method for combining multiple images of a common object assuming two-dimensional (2D) affine transformations between the image sampling grids. Our method is based upon the projection-onto-convex-sets approach of Yeh and Stark [J. Opt. Soc. Am. A 7, 491 (1990)]. Each image frame constitutes a single projection in our approach. We derive a frame projection algorithm under the 2D affine transform assumption that uses one-dimensional fast Fourier transform operations. We demonstrate that all the parameters required for successful image fusion can be estimated with sufficient accuracy from the image data proper. Four 64 x 64-pixel images taken by the Galileo Orbiter spacecraft of the asteroid Gaspra were fused to produce a result with twice the sampling rate and significantly improved spatial resolution. The total processing time was 55 s on a single-processor workstation. (C) 1998 Optical Society of America.