Improving visual quality for vector schemes

© Springer Nature Singapore Pte Ltd. 2020. To further improve the visual quality for grayscale secret images, we introduce the vector VC approach that encodes one block as a unit. First, we outline the basic vector VC for binary secret images. Then, we combine the AbS framework with vector VC to get better visual quality than AbS-based probabilistic VC and AbS-based random grid VC. For separate halftoning and VC encryption, we use the blackness preserving algorithm. For grayscale secret image, we develop an AbS-based vector VC algorithm.