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Abstract. We address the problem of segmenting an image into a previously unknown number of segments from the perspective of graph partitioning. Specifically, we consider minimum multicuts of superpixel affinity graphs in which all affinities between non-adjacent superpixels are negative. We propose a relaxation by Lagrangian decomposition and a constrained set of re-parameterizations for which we can optimize exactly and efficiently. Our contribution is to show how the planarity of the adjacency graph can be exploited if the affinity graph is non-planar. We demonstrate the effectiveness of this approach in user-assisted image segmentation and show that the solution of the relaxed problem is fast and the relaxation is tight in practice.

We propose a simple yet effective approach to content-based image retrieval: the signature matching distance. While recent approaches to content-based image retrieval utilize the bag-of-visual-words model, where image descriptors are matched through a common visual vocabulary, signaturebased approaches use a distance between signatures, i.e. between image-specific bags of locally aggregated descriptors, in order to quantify image dissimilarity. In this paper, we focus on the signature-based approach to content-based image retrieval and propose a novel distance function, the signature matching distance. This distance matches coincident visual properties of images based on their signatures. In particular, by investigating different descriptor matching strategies and their suitability to match signatures, we show that our approach is able to outperform other signature-based approaches to content-based image retrieval. Moreover, in combination with a simple color and texture-based image descriptor, our approach is able to compete with the majority of bag-of-visual-words approaches.

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We introduce a new family of flexible feature representations for content-based multimedia retrieval: probabilistic feature signatures. While conventional feature histograms and feature signatures aggregate the multimedia objects' feature distributions exhibited in some feature space according to a partitioning, probabilistic feature signatures model these feature distributions by means of discrete or continuous probability distributions. In this way, they combine the advantages of high expressiveness and compactness, for instance through Gaussian mixture models. In this paper, we introduce the concept of probabilistic feature signatures and provide the empirical evidence of high retrieval performance when using this feature representation type. We show that probabilistic feature signatures are able to outperform conventional feature signatures.