Learning to Generate Realistic Images for Bit-Depth Enhancement via Camera Imaging Processing

Abstract

With the prevalence of advanced displays devices, many attempts have been successfully made in bit-depth enhancement (BDE) to restore the low bit-depth (LBD) images to visually pleasant high bit-depth (HBD) images. However, most methods are still far from satisfactory when addressing real-world LBD images owing to their heavy dependence on LBD-HBD data pairs through direct pixel quantization. Therefore, in this paper, we propose a novel network dubbed RealGAN to generate real-world LBD images by simulating the complex quantization procedure in camera imaging process. Particularly, we design a two-mode differentiable quantization block embedded in the synthesis network facilitating adaptively simulation of the complicated quantization distortions. Furthermore, a simple residual group network is proposed in order to learn the distribution of degradation and non-linear processing in the Image Signal Processing (ISP) pipeline. In the absence of paired HBD and LBD data, the synthesis model is trained end-to-end within the generative adversarial framework using non-paired LBD and HBD images. Finally, we demonstrate that a series of BDE models can benefit from the proposed synthetic dataset and exhibit improved visual quality with sharper edges and finer textures on real-world scenes compared with the original versions trained on directly quantized LBD-HBD pairs. The codes are available at https://github.com/TJUMMG/RealGAN.

Jing Liu,Qingying Li, Huiyu Duan,Zhiwei Fan, Yuting Su,Guangtao Zhai(2025). Learning to Generate Realistic Images for Bit-Depth Enhancement via Camera Imaging Processing. IEEE Transactions on Multimedia.