1 Introduction
Human faces contain important identity information and are central to various vision applications, such as face alignment [1], [2], [3], face parsing [4], [5] and face identification [6], [7]. However, most of these applications require high-quality images as input and the approaches perform less favorably in low-resolution conditions. To alleviate the issue, the task of face hallucination, or face super-resolution, aims to super-resolve low-resolution face images to their high-resolution counterparts, thus facilitating effective face analysis.