Shadow Resistant Direct Image Registration

Direct image registration methods usually treat shadows as outliers. We propose a method which registers images in a 1D shadow invariant space. Shadow invariant image formation is possible by projecting color images, expressed in a log-chromaticity space, onto an ‘intrinsic line’. The slope of the line is a camera dependent parameter, usually obtained in a prior calibration step. In this paper, calibration is avoided by jointly determining the ‘invariant slope’ with the registration parameters. The method deals with images taken by different cameras by using a different slope for each image and compensating for photometric variations. Prior information about the camera is, thus, not required. The method is assessed on synthetic and real data.