From the point of view of information hiding

traditional visual cryptography scheme (VCS) is not an efficient method.It can only share a small sized secret image due to the large pixel expansion.A (

t

k

n

) multi-threshold image secret sharing scheme is proposed to increase the amount of hidden information.A grayscale secret image is hidden in a VCS to guide the choice of share matrices.In the first phase of the reconstruction process

any

t

participants can stack their shadow images to decode a vague secret image by human visual system.In the second phase

any

k

participants can extract additional information hidden in their shadow images

and reveal a precise grayscale secret image by computation.Comp

ared with the traditional VCS

the proposed scheme can hide more information of the grayscale secret image

and has smaller size expansion without deteriorating the visual quality of the revealed image of VCS.