Method of multiple-image hiding in QR code based on compressed sensing and orthogonal modulation

Abstract In this paper, a method of multiple-image hiding in quick response (QR) code based on compressed sensing (CS) and orthogonal modulation is presented. Using this approach, it is possible to preserve the multiple-image information perfectly in QR code. The application of CS theory can significantly reduce the amount of data processing when an image is reconstructed, and also brings a lot of convenience for the post-processing. In order to extract the images separately, orthogonal basis matrices are used to modulate the detected intensity sequences from the CS system. Hiding approach results in a QR code image which looks like normal, and the total data volume of multiple-image can be obtained after scanning and decoding the QR code. When the transpose matrix of corresponding orthogonal basis is used, the needed partial data can be extracted from the total data volume. It should be noted that only when the measurement matrix and orthogonal basis matrix are matched, the corresponding image can be reconstructed clearly. That means there are two security levels in this information hiding method. This method can also be used in the case when a huge image is divided into several parts to hide. Advantages of using orthogonal basis matrix are apparently, not only the redundant computation but also the amount of calculation can be diminished efficiently in the process of reconstruction. The feasibility of this method has been verified by the experiment, where a video projector is used to incorporate the random measurement matrices into the system.