Avoiding bleeding in image blending

Though elegant in mathematical formulation, gradient-domain image blending suffers from bleeding artefacts in real world applications. We propose an image blending algorithm that avoids bleeding artefacts while preserving the good properties of gradient-domain blending, such as smooth transitions between the candidate regions. Our key idea to finesse the non-smooth boundary difference calculation that causes bleeding artefacts is to use local patch differences. While most previous gradient-domain blending algorithms change one region to fit the other, to further reduce bleeding, we perform bidirectional blending so that both regions change simultaneously. Our blending algorithm is fast: when applied to image stitching, it can achieve 20 fps at 4K resolution. Source code and test images are publicly available.