While many image composition and synthesis techniques have been proposed, neither existing work nor professional image editing softwares such as Adobe Photoshop© provide a program explicitly for the task of realistically swapping regions within a single image. In this paper, we present an easy-to-use image-editing tool explicitly for that purpose, named as PatchSwapper. Users can simply determine the centre and radius of a pair of candidate regions or specify arbitrary borders by sketches; then, the swapping step is automatically and optimally executed. A graph-based approach is designed to find the optimal borders of two irregular regions to avoid generating visible seams. We use this approach to handle both non-transformed and transformed patches. For nontransformed cases, we not only achieve realtime performance with CPU multi-thread implementation, we also provide a location recommendation algorithm to help users find the appropriate exchangeable areas. For transformed patches, our method searches for the optimal transformation to generate interesting appearance changes on both the source and target locations. A Poisson color blending is performed onto the stitched patches. Overall the proposed approach is not only suitable for swapping image objects of any shapes but also for some other applications, e.g., image completion and composition.

The experiments demonstrate that common images often contain potentially exchangeable areas and that large content variations can be obtained by simply swapping their locations.