  Face Restoration (FR) aims to restore High-Quality (HQ) faces from
Low-Quality (LQ) input images, which is a domain-specific image restoration
problem in the low-level computer vision area. The early face restoration
methods mainly use statistic priors and degradation models, which are difficult
to meet the requirements of real-world applications in practice. In recent
years, face restoration has witnessed great progress after stepping into the
deep learning era. However, there are few works to study deep learning-based
face restoration methods systematically. Thus, this paper comprehensively
surveys recent advances in deep learning techniques for face restoration.
Specifically, we first summarize different problem formulations and analyze the
characteristic of the face image. Second, we discuss the challenges of face
restoration. Concerning these challenges, we present a comprehensive review of
existing FR methods, including prior based methods and deep learning-based
methods. Then, we explore developed techniques in the task of FR covering
network architectures, loss functions, and benchmark datasets. We also conduct
a systematic benchmark evaluation on representative methods. Finally, we
discuss future directions, including network designs, metrics, benchmark
datasets, applications,etc. We also provide an open-source repository for all
the discussed methods, which is available at
https://github.com/TaoWangzj/Awesome-Face-Restoration.
