Rank-embedded Hashing for Large-scale Image Retrieval

With the growth of images on the Internet, plenty of hashing methods are developed to handle the large-scale image retrieval task. Hashing methods map data from high dimension to compact codes, so that they can effectively cope with complicated image features. However, the quantization process of hashing results in unescapable information loss. As a consequence, it is a challenge to measure the similarity between images with generated binary codes. The latest works usually focus on learning deep features and hashing functions simultaneously to preserve the similarity between images, while the similarity metric is fixed. In this paper, we propose a Rank-embedded Hashing (ReHash) algorithm where the ranking list is automatically optimized together with the feedback of the supervised hashing. Specifically, ReHash jointly trains the metric learning and the hashing codes in an end-to-end model. In this way, the similarity between images are enhanced by the ranking process. Meanwhile, the ranking results are an additional supervision for the hashing function learning as well. Extensive experiments show that our ReHash outperforms the state-of-the-art hashing methods for large-scale image retrieval.