Abstract

MARTINEZ GONZALEZ, Pablo Arturo  and  CASTELAN, Mario. Incorporating Angular Ratio Images into Two-Frame Stereo Algorithms. Comp. y Sist. [online]. 2012, vol.16, n.1, pp.53-69. ISSN 2007-9737.

Light Transport Constancy (LTC) asserts that the reflectance ratio obtained from two different illumination variations remains constant for any given view of the observed scene. LTC was proposed in [21] as a rank constraint for solving the correspondence problem in multiple view stereo. In two-frame stereo, the simplest setting for LTC requires only two illumination variations and a single light source. Under this scenario, the rank constraint can be formulated through ratio images, and standard stereo algorithms can be applied in order to obtain a disparity map. Unfortunately, a ratio image may be subject to saturated pixel values, and this may diminish the quality of disparity maps. To solve this problem, as a first contribution in this work, we propose a post-processing operation based on slope angles related to the ratio values. Experiments show that new angular ratio images are more robust and deliver improved disparity maps. A second contribution of this paper consists in performing an experimental evaluation of angular ratio images under the standard test bed for two-view stereo algorithms, i.e., using different aggregation and optimization approaches. The results of our research are consistent with previously reported conclusions for two-view stereo surveys. It means that LTC may benefit from a vast variety of existent methods to solve the two-view stereo problem.

Keywords : Light Transport Constancy; two-frame stereo; ratio images.