A robust flash image shadow detection method and seamless recovery of shadow regions

In low or moderate ambient light conditions, flash image is sharp and less noisy as compared to no-flash image; however, it contains unwanted sharp shadows at silhouettes. In our previous work, we proposed a new flash image shadow detection method which utilizes a pair of flash/no-flash images to detect sharp shadows at silhouettes; however, the method often leads to false shadow detection due its inability to effectively discriminate dark background areas. In this paper, we present an enhanced shadow detection algorithm which shows significant improvement in detection results. A seamless cloning method is used to fill detected shadow regions using no-flash image information. A quantitative as well as qualitative comparison of the proposed shadow detection method on our flash/no-flash image dataset shows that it outperforms current state-of-the-art shadow detection algorithms, both in terms of accuracy as well as speed. The qualitative results of proposed shadow recovery technique show that it generates good quality resultant flash images without sharp shadows.