Few but Informative Local Hash Code Matching for Image Retrieval

Content-based image retrieval (CBIR) aims to search for the most similar images from an extensive database to a given query content. Existing CBIR works either represent each image with a compact global feature vector or extract a large number of highly compressed low-dimensional local features, where each contains limited information. In this research study, we propose an expressive local feature extraction pipeline and a many-to-many local feature matching method for large-scale CBIR. Unlike existing local feature methods, which tend to extract large amounts of low-dimensional local features from each image, the proposed method models characteristic feature representations for each image, aiming to employ fewer but more expressive local features. For further improving the results, an end-to-end trainable hash encoding layer is used for extracting compact but informative codes from images. The proposed many-to-many local feature matching is then directly performed on the hash feature vectors from input images, leading to new state-of-the-art performance on several benchmark datasets.