Boundary-Guided Optimization Framework for Saliency Refinement

Abstract

Salient object detection has made a rapid progress in recent years. To improve the quality of initial saliency maps, existing algorithms typically refine them via a neighbor-constrained smoothing model, which assigns similar saliency values to neighboring regions. Since the adjacent regions could also cross the boundary between the salient object and background, these spatial distance-based methods easily cause false detection by involving the background regions that are close to the salient objects. To address this problem, we propose a boundary-guided optimization framework to jointly improve the region smoothness and correct the false detect regions. Specifically, we introduce a latent segmentation variable to regularize the consistency between the refined saliency map and the latent segmentation mask, which penalizes high (low) saliency values of the regions lying outside (inside) the estimated object boundary. To optimize the proposed objective function, we decompose the primary problem into two subproblems: submodular optimization problem and convex optimization problem. The submodular optimization problem can be quickly optimized using the off-the-shelf technique while the convex optimization can be solved with a closed-form solution. The experimental results show that the proposed method consistently improve the performances of eight state-of-the-art salient object detection algorithms on three datasets, including latest deep convolutional neural network-based algorithms. Meanwhile, our method outperforms state-of-the-art saliency refinement algorithms.