Mobile multi-flash photography

Xinqing Guo, Jin Sun, Zhan Yu, Haibin Ling, Jingyi Yu

Abstract: Multi-flash (MF) photography offers a number of advantages over regular photography including removing the effects of illumination, color and texture as well as highlighting occlusion contours. Implementing MF photography on mobile devices, however, is challenging due to their restricted form factors, limited synchronization capabilities, low computational power and limited interface connectivity. In this paper, we present a novel mobile MF technique that overcomes these limitations and achieves comparable performance as conventional MF. We first construct a mobile flash ring using four LED lights and design a special mobile flash-camera synchronization unit. The mobile device’s own flash first triggers the flash ring via an auxiliary photocell. The mobile flashes are then triggered consecutively in sync with the mobile camera’s frame rate, to guarantee that each image is captured with only one LED flash on. To process the acquired MF images, we further develop a class of fast mobile image processing techniques for image registration, depth edge extraction, and edge-preserving smoothing. We demonstrate our mobile MF on a number of mobile imaging applications, including occlusion detection, image thumbnailing, image abstraction and object category classification.