Contrast-Enhanced Color Visual Cryptography for (k, n) Threshold Schemes

Zuquan LIU, Guopu ZHU*, Feng DING, Xiangyang LUO, Sam KWONG, Peng LI

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)peer-review

7 Citations (Scopus)


In traditional visual cryptography schemes (VCSs), pixel expansion remains to be an unsolved challenge. To alleviate the impact of pixel expansion, several colored-black-and-white VCSs, called CBW-VCSs, were proposed in recent years. Although these methods could ease the effect of pixel expansion, the reconstructed image obtained by these methods may also suffer from low contrasts. To address this issue, we propose a contrast-enhanced (k, n) CBW-VCS based on random grids, named (k,n) RG-CBW-VCS, in this article. By applying color random grids, a binary secret image is encrypted into n color shares that have no pixel expansion. When any k1 (k1> k) color shares are collected together, the stacked results of them can be identified as the secret image; whereas the superposition of any k2 (k2< k) color shares shows nothing. Through theoretical analysis and experimental results, we justify the effectiveness of the proposed (k, n) RG-CBW-VCS. Compared with related methods in feature, contrast, and pixel expansion, the results indicate that the proposed method generally achieves better performance.

Original languageEnglish
Article number148
Number of pages16
JournalACM Transactions on Multimedia Computing, Communications and Applications
Issue number3
Publication statusPublished - Oct 2022
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported in part by the National Natural Science Foundation of China under Grant 62172402, Grant 61872350, Grant U1804263, and Grant 62172435, in part by the Zhongyuan Science and Technology Innovation Leading Talent Project of China under Grant 214200510019, in part by the Tip-top Scientific and Technical Innovative Youth Talents of Guangdong Special Support Program under Grant 2019TQ05X696, and in part by the Basic Research Program of Shenzhen under Grant JCYJ20170818163403748.

Publisher Copyright:
© 2022 Association for Computing Machinery.


  • contrast enhancement
  • pixel expansion
  • random grid
  • threshold scheme
  • Visual cryptography


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