Salient Object Detection using concavity context

Convexity (concavity) is a bottom-up cue to assign figure-ground relation in the perceptual organization [18]. It suggests that region on the convex side of a curved boundary tend to be figural. To explore the validity of this cue in the task of salient object detection, we segment the images in a test dataset into superpixels, and then locate the concave arcs and their bounding boxes along boundary of superpixels. Ecological statistics indicate that such bounding box contains salient object with a large probability. To utilize this spatial context information, i.e. concavity context, we follow the multi-scale analysis of human visual perception and design a hierarchical model. The model yields an affinity graph over candidate superpixels, in which weights between vertices are determined by the summation of concavity context on different scales in the hierarchy. Finally a graph-cut algorithm is performed to separate the salient and background objects. Evaluation on MSRA Salient Object Detection (SOD) dataset shows that concavity context is effective, and our approach provides improvement over state-of-the-art feature-based algorithms.