Binary Representation Learning for Large Scale Visual Data

The exponentially growing modern media created large amount of multimodal or multidomain visual data, which usually reside in high dimensional space. And it is crucial to provide not only effective but also efficient understanding of the data.In this dissertation, we focus on learning binary representation of visual dataset, whose primary use has been hash code for retrieval purpose. Simultaneously it serves as multifunctional feature that can also be used for various computer vision tasks. Essentially, this is achieved by discriminative learning that preserves the supervision information in the binary representation.By using deep networks such as convolutional neural networks (CNNs) as backbones, and effective binary embedding algorithm that is seamlessly integrated into the learning process, we achieve state-of-the art performance on several settings. First, we study the supervised binary representation learning problem by using label information directly instead of pairwise similarity or triplet loss. By considering images and associated textual information, we study the cross-modal representation learning. CNNs are used in both image and text embedding, and we are able to perform retrieval and prediction across these modalities. Furthermore, by utilizing unlabeled images from a different domain, we propose to use adversarial learning to connect these domains. Finally, we also consider progressive learning for more efficient learning and instance-level representation learning to provide finer granularity understanding. This dissertation demonstrates that binary representation is versatile and powerful under various circumstances with different tasks

Zero-Shot Hashing via Transferring Supervised Knowledge

Hashing has shown its efficiency and effectiveness in facilitating large-scale multimedia applications. Supervised knowledge e.g. semantic labels or pair-wise relationship) associated to data is capable of significantly improving the quality of hash codes and hash functions. However, confronted with the rapid growth of newly-emerging concepts and multimedia data on the Web, existing supervised hashing approaches may easily suffer from the scarcity and validity of supervised information due to the expensive cost of manual labelling. In this paper, we propose a novel hashing scheme, termed \emph{zero-shot hashing} (ZSH), which compresses images of "unseen" categories to binary codes with hash functions learned from limited training data of "seen" categories. Specifically, we project independent data labels i.e. 0/1-form label vectors) into semantic embedding space, where semantic relationships among all the labels can be precisely characterized and thus seen supervised knowledge can be transferred to unseen classes. Moreover, in order to cope with the semantic shift problem, we rotate the embedded space to more suitably align the embedded semantics with the low-level visual feature space, thereby alleviating the influence of semantic gap. In the meantime, to exert positive effects on learning high-quality hash functions, we further propose to preserve local structural property and discrete nature in binary codes. Besides, we develop an efficient alternating algorithm to solve the ZSH model. Extensive experiments conducted on various real-life datasets show the superior zero-shot image retrieval performance of ZSH as compared to several state-of-the-art hashing methods.Comment: 11 page