A method for visual encryption of gray-scale image

Abstract

The invention discloses a gray image visual encryption method. In this method, two processes are placed in an error-diffusion feedback loop, which are the generation of split-memory image and the superposition decoding of visual cryptography. Which means, at the encoder end, each pixel or image block is sequentially processed in a scanning order, for each pixel or image block on the resulting split image, check its superposition decoding effect immediately, comparing the reconstructed target image obtained after superposition with the original secret image, obtaining the difference between thetwo, the contrast difference is fed back and diffused to surrounding pixels or image blocks that have not yet been quantized, so as to improve the quality of decoded and reconstructed secret images,wherein the analysis process corresponds to a process of generating a split image from the secret image and the synthesis process corresponds to a process of obtaining a target image from the split image, and the method of the invention places the synthesis in an analysis, that is, an analysis based on the 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

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