Attention-Aware Feature Pyramid Ordinal Hashing for Image Retrieval

Due to the effectiveness of representation learning, deep hashing methods have attracted increasing attention in image retrieval. However, most existing deep hashing methods merely encode the raw information of the last layer for hash learning, which result in the following deficiencies: (1) the useful information from the preceding-layer is not fully exploited; (2) the local salient information of the image is neglected. To this end, we propose a novel deep hashing method, called Attention-Aware Feature Pyramid Ordinal Hashing (AFPH), which explores both the visual structure information and semantic information from different convolutional layers. Specifically, two feature pyramids based on spatial and channel attention are well constructed to capture the local salient structure from multiple scales. Moreover, a multi-scale feature fusion strategy is proposed to aggregate the feature maps from multi-level pyramidal layers to generate the discriminative feature for ranking-based hashing. The experimental results conducted on two widely-used image retrieval datasets demonstrate the superiority of our method.