The performance of face photo-sketch translation has improved a lot thanks to
deep neural networks. GAN based methods trained on paired images can produce
high-quality results under laboratory settings. Such paired datasets are,
however, often very small and lack diversity. Meanwhile, Cycle-GANs trained
with unpaired photo-sketch datasets suffer from the \emph{steganography}
phenomenon, which makes them not effective to face photos in the wild. In this
paper, we introduce a semi-supervised approach with a noise-injection strategy,
named Semi-Cycle-GAN (SCG), to tackle these problems. For the first problem, we
propose a {\em pseudo sketch feature} representation for each input photo
composed from a small reference set of photo-sketch pairs, and use the
resulting {\em pseudo pairs} to supervise a photo-to-sketch generator
$G_{p2s}$. The outputs of $G_{p2s}$ can in turn help to train a sketch-to-photo
generator $G_{s2p}$ in a self-supervised manner. This allows us to train
$G_{p2s}$ and $G_{s2p}$ using a small reference set of photo-sketch pairs
together with a large face photo dataset (without ground-truth sketches). For
the second problem, we show that the simple noise-injection strategy works well
to alleviate the \emph{steganography} effect in SCG and helps to produce more
reasonable sketch-to-photo results with less overfitting than fully supervised
approaches. Experiments show that SCG achieves competitive performance on
public benchmarks and superior results on photos in the wild.

本文介绍一种半监督方法，即带有噪声注入策略的 Semi-Cycle-GAN (SCG)，用于解决面部照片素描翻译中的配对数据集小且缺乏多样性以及来自不匹配照片 - 素描数据集所带来的隐写学现象等问题。实验证明 SCG 在公共基准测试中具有竞争性的性能，并且在野外照片上表现出优越的结果。