A Visual Encryption Method for Grayscale Image

Abstract

The invention discloses a grayscale image visual encryption method. In this method, the two processes of image generation and superposition decoding in visual cryptography are placed in an error diffusion feedback loop. That is to say, at the encoder side, each pixel or image block is sequentially processed according to a certain scanning order, and for each pixel or image block on the generated shared image, the superimposed decoding effect is checked immediately, and the superimposed obtained The reconstructed target image is compared with the original secret image to obtain the difference between the two, and the contrast difference is fed back and diffused to surrounding pixels or image blocks that have not been quantified, so as to improve the quality of the decoded and reconstructed secret image. The process of generating shared images, and the synthesis process corresponds to the process of obtaining target images from shared images, the method of the present invention puts synthesis in analysis, that is, analysis based on synthesis.

Description

technical field [0001] The invention relates to the field of multimedia communication security, in particular to a grayscale image visual encryption method. Background technique [0002] Visual encryption is a secret sharing method that is efficient in the decoding process and does not require any calculation. For a (n,k) threshold visual cipher, it divides a secret image into n parts for transmission, and only obtains at least k of them. It is superimposed to recover the contents of the secret image. In recent years, research on visual cryptography has two focuses: one is to reduce the size of the shared image, and the other is to improve the visual quality of the reconstructed image. Among them, the size of the shared image is generally expanded compared to the size of the secret image. A small expansion factor or even a visual cryptography with no expansion in size has many advantages, such as low processing complexity, small storage space, and low transmission bandwidth...

AI Technical Summary

Problems solved by technology

Recently, X.T.Wu et al. proposed a visual cryptography that can generate blue noise shared images. However, after superimposing two blue noise shared images, the reconstructed image will no longer have blue noise characteristics, so this type of algorithm is only suitable for gray images. The high-degree secret image is simply binarized and then encrypted, so it has very low detail resolution ability

Images