Geometry-aware Relational Exemplar Attention for Dense Captioning

Dense captioning (DC), which provides a comprehensive context understanding of images by describing all salient visual groundings in an image, facilitates multimodal understanding and learning. As an extension of image captioning, DC is developed to discover richer sets of visual contents and to generate captions of wider diversity and increased details. The state-of-the-art models of DC consist of three stages: (1) region proposals, (2) region classification, and (3) caption generation for each proposal. They are typically built upon the following ideas: (a) guiding the caption generation with image-level features as the context cues along with regional features and (b) refining locations of region proposals with caption information. In this work, we propose (a) a joint visual-textual criterion exploited by the region classifier that further improves both region detection and caption accuracy, and (b) a Geometry aware Relational Exemplar attention (GREatt) mechanism to relate region proposals. The former helps the model learn a region classifier by effectively exploiting both visual groundings and caption descriptions. Rather than treating each region proposal in isolation, the latter relates regions in complementary relations, i.e. contextually dependent, visually supported and geometry relations, to enrich context information in regional representations. We conduct an extensive set of experiments and demonstrate that our proposed model improves the state-of-the-art by at least +5.3% in terms of the mean average precision on the Visual Genome dataset.