Direct Binary Search Based Algorithms for Image Hiding

Abstract

Digital halftoning is an important process to convert a continuous-tone image into a binary image with pure black and white pixels. The Direct Binary Search (DBS) is one of the well-known halftoning methods that can generate high quality binary images. The main contribution of this paper is to present a DBS based halftoning method that conceals a binary image into two binary images. More specifically, three distinct gray scale images are given, such that one of them should be hidden in the other two gray scale images. Our DBS based halftoning method generates three binary images that reproduce the tone of the corresponding original three gray scale images. Quite surprisingly, the secret binary image can be seen by overlapping the other two binary images. In other words, the secret binary image is hidden in two public binary images. Also, it is very hard to guess the secret images using only one of the two public images, and both of these two public images are necessary to get the secret image. Another contribution of this paper is to extend our DBS based halftoning method to hide one image and more than one image into more than two images. The resulting images show that our DBS based halftoning method hides and recovers the original images. Hence, our DBS based halftoning technique can be used for watermarking as well as amusement purpose.