Fan-ring interpolation method applied to the panorama unwrapping of the deep-hole parts

Image interpolation is a critical step in panoramic image unwrapping studies. Information calculated in the Cartesian coordinates, although broadly applied, applies to operation between rectangles that will destroy the compressed depth information. The polar coordinates, in contrast, can store depth information by handing between rectangle and circle to obtain more true images. A fan-ring interpolation based on the polar coordinates is proposed for unwrapping panoramic images in this study through replanning the pixel search path in the panorama, and is then supported by redefining third-order interpolation. We validate our method on synthetic and practical images. Compared with competitor models, the unwrapping image obtained from the fan-ring interpolation can provide better quality in subjective and objective evaluation with guaranteed accuracy.