A morphological fusion algorithm for optical detection and quantification of decay patterns on stone surfaces

The quantification of black crust formation on exposed stone has been carried out in this work with the aid of non-destructive analytical techniques. The proposed non-destructive Morphologically Fused Detection (MFD) approach, quantifies the deterioration effects encountered on marble surfaces by providing the number, location and shape of deterioration spots. According to this approach, a weighted difference of Gaussians filter determines the exact locations of deterioration patterns, a morphological detector provides the shape of such patterns and finally a conditional thickening operator combines location and shape information from the previous stages. The detected decay areas are segmented and distinguished into white and black spots according to their chemical composition. Besides applications in assessing deterioration and monitoring the decay rate of exposed stone with time, MFD can be further employed for evaluating the efficiency of cleaning methods. The algorithm is tested on a large set of images depicting a variety of degradation effects. The derived results are in accordance with assessments obtained by chemical analyses.