Capturing screen contents by smartphone cameras has become a common way for information sharing. However, these images and videos are often degraded by moiré patterns, which are caused by frequency aliasing between the camera filter array and digital display grids. We observe that the moiré patterns in raw domain is simpler than those in sRGB domain, and the moiré patterns in raw color channels have different properties. Therefore, we propose an image and video demoiréing network tailored for raw inputs. We introduce a color-separated feature branch, and it is fused with the traditional feature-mixed branch via channel and spatial modulations. Specifically, the channel modulation utilizes modulated color-separated features to enhance the color-mixed features. The spatial modulation utilizes the feature with large receptive field to modulate the feature with small receptive field. In addition, we build the first well-aligned raw video demoiréing (RawVDemoiré) dataset and propose an efficient temporal alignment method by inserting alternating patterns. Experiments demonstrate that our method achieves state-of-the-art performance for both image and video demoiréing. Our dataset and code will be released after the acceptance of this work.

Capturing screen content by smart-phone cameras has become a daily routine to record or share instant information from display screens for convenience. However, these recaptured screen images are often degraded by moiré patterns and usually present color cast against the original screen source. We observe that performing demoiréing in raw domain before feeding into the image signal processor (ISP) is more effective than demoiréing in the sRGB domain as done in recent demoiréing works. In this paper, we investigate the demoiréing of raw images through a class-specific learning approach. To this end, we build the first well-aligned raw moiré image dataset by pixel-wise alignment between the recaptured images and source ones. Noting that document images occupy a large portion of screen contents and have different properties from generic images, we propose a class-specific learning strategy for textual images and natural color images. In addition, to deal with moiré patterns with various scales, a multi-scale encoder with multi-level feature fusion is proposed. The shared encoder enables us to extract rich representations for the two kinds of contents and the class-specific decoders benefit the specific content reconstruction by focusing on targeted representations. Experiment results demonstrate that our method achieves state-of-the-art demoiréing performance. We have released the code and dataset inhttps://github.com/tju-chengyijia/RDNet