“…In the next subsections we present some fundamental concepts on graphs, and four image-graph representation approaches: based on the Pixel Grid (Shi & Malik, 2000) , Multiscale Pixel Grid (Cour et al, 2005), based on the Component Tree (Carvalho, Costa, Ferreira & Cesar-Jr., 2010), and based on the Quadtree . Approaches based on the Component Tree, Quadtree,andMultiscale Pixel Grid rely on hierarchical structures to model an image as a graph, and provide different segmentation results when compared to the classical non-hierarchical pixel grid approach.…”