Colour Constancy Techniques for Re-Recognition of Pedestrians from Multiple Surveillance Cameras

Abstract : This paper presents work towards a system for tracking the movements of a pedestrian as they move between the multiple sensors comprising a surveillance system. The colour appearance of the observations is an important cue: it is useful to achieve good color constancy between the color values associated with each camera. A novel method for estimating the appropriate transform between each camera's colour space is proposed, using covariance of the foreground data collected from each camera. Simulations are used to demonstrate that the method only works if the covariance has a sufficiently high ratio between its eigenvalues. The covariance matrices for foreground data collected from 29 surveillance cameras are estimated and shown to have a sufficiently high ratio. The discriminative power of colour-based appearance descriptors is evaluated using several types of colour constancy methods. The proposed method leads to a significant improvement in the simplest and best performing (mean) colour descriptor. It is shown how these descriptors can be integrated into a probabilistic framework for tracking pedestrians from multiple surveillance cameras.