  Zero-Shot Hashing aims at learning a hashing model that is trained only by
instances from seen categories but can generate well to those of unseen
categories. Typically, it is achieved by utilizing a semantic embedding space
to transfer knowledge from seen domain to unseen domain. Existing efforts
mainly focus on single-modal retrieval task, especially Image-Based Image
Retrieval (IBIR). However, as a highlighted research topic in the field of
hashing, cross-modal retrieval is more common in real world applications. To
address the Cross-Modal Zero-Shot Hashing (CMZSH) retrieval task, we propose a
novel Attribute-Guided Network (AgNet), which can perform not only IBIR, but
also Text-Based Image Retrieval (TBIR). In particular, AgNet aligns different
modal data into a semantically rich attribute space, which bridges the gap
caused by modality heterogeneity and zero-shot setting. We also design an
effective strategy that exploits the attribute to guide the generation of hash
codes for image and text within the same network. Extensive experimental
results on three benchmark datasets (AwA, SUN, and ImageNet) demonstrate the
superiority of AgNet on both cross-modal and single-modal zero-shot image
retrieval tasks.
