Enhanced Median Flow Tracker for Videos with Illumination Variation Based on Photometric Correction
Asha Narayana and Narasimhadhan Venkata
Department of Electronics and Communication
Engineering, National Institute of Technology Karnataka, India
Abstract: Object tracking is a
fundamental task in video surveillance, human-computer interaction and activity
analysis. One of the common challenges in
visual object tracking is illumination variation. A large number of methods for
tracking have been proposed over the recent years, and median flow tracker is one
of them which can handle various
challenges. Median flow tracker is designed to track an object using
Lucas-Kanade optical flow method which is sensitive to illumination variation, hence fails when sudden illumination changes
occur between the frames. In this paper, we propose an enhanced median flow
tracker to achieve an illumination invariance to abruptly varying lighting
conditions. In this approach, illumination variation is compensated by modifying the Discrete Cosine Transform (DCT)
coefficients of an image in the logarithmic domain. The illumination variations
are mainly reflected in the low-frequency coefficients of an image. Therefore, a fixed number of DCT
coefficients are ignored. Moreover, the Discrete Cosine (DC) coefficient is
maintained almost constant all through the video based on entropy difference to
minimize the sudden variations of lighting
impacts. In addition, each video frame is enhanced by employing pixel transformation
technique that improves the contrast of dull images based on probability distribution of pixels. The
proposed scheme can effectively handle
the gradual and abrupt changes in the illumination of the object. The
experiments are conducted on fast-changing illumination videos, and results show that the proposed method
improves median flow tracker with outperforming accuracy compared to the state-of-the-art trackers.
Keywords: Illumination variation, median flow
tracker, entropy, gamma correction.
Received April 6,
2017; accepted April 25, 2018