  Screen content images typically contain a mix of natural and synthetic image
parts. Synthetic sections usually are comprised of uniformly colored areas and
repeating colors and patterns. In the VVC standard, these properties are
exploited using Intra Block Copy and Palette Mode. In this paper, we show that
pixel-wise lossless coding can outperform lossy VVC coding in such areas. We
propose an enhanced VVC coding approach for screen content images using the
principle of soft context formation. First, the image is separated into two
layers in a block-wise manner using a learning-based method with four block
features. Synthetic image parts are coded losslessly using soft context
formation, the rest with VVC.We modify the available soft context formation
coder to incorporate information gained by the decoded VVC layer for improved
coding efficiency. Using this approach, we achieve Bjontegaard-Delta-rate gains
of 4.98% on the evaluated data sets compared to VVC.

Image and Video Processing;Multimedia