The naturalness of warps is gaining extensive attentions in image stitching. Recent warps such as SPHP and AANAP, use global similarity warps to mitigate projective distortion (which enlarges regions), however, they necessarily bring in perspective distortion (which generates inconsistencies). In this paper, we propose a novel quasi-homography warp, which effectively balances the perspective distortion against the projective distortion in the non-overlapping region to create a more natural-looking panorama. Our approach formulates the warp as the solution of a bivariate system, where perspective distortion and projective distortion are characterized as slope preservation and scale linearization respectively. Because our proposed warp only relies on a global homography, thus it is totally parameter-free. A comprehensive experiment shows that a quasi-homography warp outperforms some state-of-the-art warps in urban scenes, including homography, AutoStitch and SPHP. A user study demonstrates that it wins most users' favor, comparing to homography and SPHP.

Two lignan sulfates, a stilbene derivative and a phenol sulfate, together with 10 known compounds, were isolated from an aqueous extract of the root of Polygonum cuspidatum. The new compounds were elucidated based on chemical evidence and spectroscopic techniques including two-dimensional NMR methods. They exhibited no inhibition of lipid peroxidation and no cytotoxic and DNA cleavage activities.

Ten naturally occurring stilbene glycoside sulfates (1-10) were isolated from an aqueous extract of the root of Polygonum cuspidatum. Their structures were established based on chemical evidence and spectroscopic techniques, including 2D NMR methods.