Multimodal Target Detection by Sparse Coding: Application to Paint Loss Detection in Paintings

Sparse representation based methods have demonstrated their superior performance in target detection tasks compared to more traditional approaches such as matched subspace detectors and adaptive subspace detectors. However, the existing sparsity-based target detection methods were mostly formulated for and validated on a single imaging modality (sometimes with multiple spectral bands). In many application domains, including art investigation, multimodal data, acquired by different sensors are readily available, and yet, efficient processing techniques for such data are still scarce. In this paper, we propose a sparsity-based multimodal target detection method that processes jointly the information from multiple imaging modalities in a kernel feature space, and making use of the spatial context. We develop our target detector such to be robust to errors in labelled data, which is especially important in applications like digital painting analysis, where pixel-wise manual annotations are unreliable. We apply the proposed method to a challenging application of paint loss detection in master paintings and we demonstrate its effectiveness on a case study with multimodal acquisitions of the Ghent Altarpiece.