Left : A ground-truth partitioning ( top ) and a computationally determined partitioning ( bottom ). Right: The corresponding overlap graph with four connected components. In the overlap graph, we introduce one vertex for each ground-truth cell (i.e., color), which constitutes the top layer. In the bottom layer, we introduce one vertex for each color in the computed partitioning. We introduce an edge between two vertices if and only if at least one segment receives the corresponding colors in the ground-truth partitioning and the computed partitioning, respectively. Connected components that consist of one edge only constitute correct assignments. Those components involving only one vertex on either side represent over- or under-partitionings, respectively. Connected components with more than one vertex on both sides constitute mis-partitionings.