Image Similarity Based on Intensity Scaling

• Authors: Stephen L. Keeling
• Venue: Journal of Mathematical Imaging and Vision
• Year: 2007

An image similarity measure based upon intensity scaling is investigated for the registration of images which differ in contrast. The measure is introduced for both optical flow and for finite displacements, and registration by the optical flow formulation is found to be independent of image order. While other morphological image matching methods involve differential formulations, the present work simply involves composition with scaling functions. Such rescaling is additionally found to have a smoothing effect on noisy images. Results obtained by Tikhonov regularization of scaling functions are superior to those obtained by a restricted set of basis functions. Computational results are performed for simple test cases as well as for realistic examples taken from magnetic resonance imaging. It is found that the computational cost for the implementation of scaling functions is very small, and yet the resulting image similarity can provide a match between images with smaller errors than that obtained by a sum of squared differences alone. In particular, images which are morphologically equivalent but which are scaled differently and even have different noise levels can be well matched with the scaling functions approach while the sum of squared differences would be unsuitable. In addition, matching is improved for image pairs in which contrast agent or an intensity modulation appears in one image and not in the other.