Global–local–global context-aware network for salient object detection in optical remote sensing images

For the salient object detection in optical remote sensing images (ORSI-SOD), many existing methods are trapped in a local–global mode, i.e., CNN-based encoder binds with a specific global context-aware module, struggling to deal with the challenging ORSIs with complex background and scale-variant objects. To solve this issue, we explore the synergy of the global-context-aware and local-context-aware modeling and construct a preferable global–local–global context-aware network (GLGCNet). In the GLGCNet, a transformer-based encoder is adopted to extract global representations, combining with local-context-aware features gathered from three saliency-up modules for comprehensive saliency modeling, and an edge assignment module is additionally employed to refine the preliminary detection. Specifically, the saliency-up module involves two components, one for global–local context-aware transfer towards pixel-wise dynamic convolution parameters prediction, the other for dynamically local-context aware modeling. The corresponding position-sensitive filter is aware of its previous global-wise focus, thus enhancing the spatial compactness of salient objects and encouraging the feature upsampling achievement for multi-scale feature combinations. The edge assignment module enhances the robustness of preliminary saliency prediction and assigns the semantic attributes of preliminary saliency cues to the shallow-level edge feature to obtain final complete salient objects in a spatially and semantically global manner. Extensive experiments demonstrate that the proposed GLGCNet surpasses 23 state-of-the-art methods on three popular datasets.