1. An image processing system for calculating transformation parameters to register a first image to a second image, the first and second images representing at least partially overlapping portions of a scene, the system comprising: one or more processors; and memory including instructions that, when executed on the one or more processors, configure the one or more processors to: receive data corresponding to the first and second images; calculate, from the received data, first and second gradients of the first and second images, respectively, the first and second gradients having respective phases that indicate a direction of greatest change in the first and second images, respectively; and calculate, from the first and second gradients, estimated parameters of a coordinate transformation that maps the first gradient to the second gradient, the estimated parameters being calculated using spatiotemporal derivatives and without relying on features in the first or second images.