Deep Photo Relighting by Integrating Both 2D and 3D Lighting Information

In this paper, we propose a novel framework called “deep photo relighting” (DPR) that can transform the lighting condition of an image for a virtual test of image detection/classification algorithm, city environment design, and data augmentation for machine learning. Our framework employs the deep neural network (DNN) approach based on U-Net. Specifically, DPR has two keypoints for transforming one lighting condition to another one by DNN. One is that we can support all factors that affect the lighting conditions (e.g., viewpoint, object materials/geometry, light position) by using 2D and 3D information such as omnidirectional image, omnidirectional depth image, and region segmentation image. The other keypoint is that we can reproduce indirect influences from outside the frame such as shadow by grasping the whole lighting environment with omnidirectional image/depth. As a result, DPR can generate relighting image without fatal artifacts such an unnatural shading/shadows of objects. In experiments, we confirmed that a generated image is well reproduced compared with the ground truth image. We also confirmed that shadows, which occur inside and outside the frame through obstacles, are properly added/deleted in the generated image compared with the ground truth image.