Illuminant-tilt estimation from images of isotropic texture

The authors present a new illuminant-tilt-angle estimator that works with isotropic textures. It has been developed from Kube and Pentland´s (1988) frequency-domain model of images of three-dimensional texture, and is compared with Knill´s (1990) spatial-domain estimator. The frequency and spatial-domain theory behind each of the estimators is related via an alternative proof of the basic phenomena that both estimators exploit: that is that the variance of the partial derivative of the image is at a maximum when the partial derivative is taken in the direction of the illuminant´s tilt. Results obtained using both simulated and real textures suggest that the frequency-domain estimator is more accurate