Ordinal Deep Learning for Facial Age Estimation
In this paper, we propose an ordinal deep learning approach for facial age estimation. Unlike conventional hand-crafted feature-based methods that require prior and expert knowledge, we propose an ordinal deep feature learning (ODFL) method to learn feature descriptors for face representation directly from raw pixels. Motivated by the fact that age labels are chronologically correlated and age estimation is an ordinal learning problem, our proposed ODFL enforces two criteria on the descriptors, which are learned at the top of the deep networks: 1) the topology-preserving ordinal relation is employed to exploit the order information in the learned feature space and 2) the age-difference cost information is leveraged to dynamically measure face pairs with different age value gaps. However, both the procedures of feature extraction and age estimation are learned independently in ODFL, which may lead to a sub-optimal problem. To address this, we further propose an end-to-end ordinal deep learning (ODL) framework, where the complementary information of both the procedures is exploited to reinforce our model. Extensive experimental results on five face aging datasets show that both our ODFL and ODL achieve superior performance in comparisons with most state-of-the-art methods.