Bi-directional Object-Context Prioritization Learning for Saliency Ranking

The saliency ranking task is recently proposed to study the visual behavior that humans would typically shift their attention over different objects of a scene based on their degrees of saliency. Existing approaches focus on learning either object-object or object-scene relations. Such a strategy follows the idea of object-based attention in Psychology, but it tends to favor objects with strong semantics (e.g., humans), resulting in unrealistic saliency ranking. We observe that spatial attention works concurrently with object-based attention in the human visual recognition system. During the recognition process, the human spatial attention mechanism would move, engage, and disengage from region to region (i.e., context to context). This inspires us to model region-level interactions, in addition to object-level reasoning, for saliency ranking. Hence, we propose a novel bi-directional method to unify spatial attention and object-based attention for saliency ranking. Our model has two novel modules: (1) a selective object saliency (SOS) module to model object-based attention via inferring the semantic representation of salient objects, and (2) an object-context-object relation (OCOR) module to allocate saliency ranks to objects by jointly modeling object-context and context-object interactions of salient objects. Extensive experiments show that our approach outperforms existing state-of-the-art methods. Code and pretrained model are available at https://github.com/GrassBro/OCOR.