Near-optimal pitch of a moiré grating for image hiding applications in dynamic visual cryptography

Dynamic visual cryptography is based on hiding of a dichotomous secret image in the regular moiré grating. One pitch of the moiré grating is used to represent the secret image and a slightly different pitch of another moiré grating is used to form the background. The secret is decoded in the form of a pattern of a time-averaged moiré fringe when the cover image is oscillated according to a predefined law of motion. The security of the encoding and the sharpness of the decoded secret are mostly influenced by the selection of the pitches of moiré grating. This paper proposes scheme for the determination of near-optimal pitches of the moiré grating for image hiding in dynamic visual cryptography

Dynamic visual cryptography scheme on the surface of a vibrating structure

Dynamic visual cryptography scheme based on time-averaged fringes generated by Ronchi-type geometric moiré gratings on finite element grids is proposed in this paper. A single cover image is used to encode the secret image and is formed on the surface of a deformable structure. Time-averaged moiré fringes leak the secret when the structure is oscillated according to a predefined Eigen-shape. The envelope functions determining the motion induced blur of the Ronchi-type moiré grating depend on the characteristic features of the motion. And though harmonic oscillations do not result into a completely uniform time-averaged image of the Ronchi-moiré grating, initial phase scrambling and phase normalization algorithms are used to encode the secret in the cover image. Theoretical relationships between the amplitude of the Eigen-shape, the order of the not completely developed time-averaged fringe and the pitch of the deformable one-dimensional Ronchi-type moiré grating are derived

Numerical analysis of the volume and the energy value of a pool of peat

In this paper we present the equations for determining the volume of the pool of peat for a set of given three-dimensional coordinates. The discrete approach is discussed and tested for additive noise also. Such an approach can be successfully applied in estimating the energy value of a pool of peat. By evaluating the sets of each adjacent points the local properties of peat can be carried out through the calculations

A robust scheme for the identification of centerlines of moiré fringes from optical experimental images

A robust scheme for the identification of centerlines of moiré fringes from optical experimental images is proposed in this paper. The proposed computational algorithm comprises three basic steps: the thresholding of the experimental image, thinning of the projected grating based on morphological and mid-point detection rules and, finally, the reconstruction of the map of continuous curves from the binary matrix of pixels representing fringe centerlines. The first steps can be considered as adaptations of standard image processing techniques, while the identification and the reconstruction of continuous curves is the original contribution specifically developed for optical projection moiré images. The functionality of such an approach is demonstrated for a demanding optical experimental image

A robust scheme for the identification of centerlines of moiré fringes from optical experimental images

A robust scheme for the identification of centerlines of moiré fringes from optical experimental images is proposed in this paper. The proposed computational algorithm comprises three basic steps: the thresholding of the experimental image, thinning of the projected grating based on morphological and mid-point detection rules and, finally, the reconstruction of the map of continuous curves from the binary matrix of pixels representing fringe centerlines. The first steps can be considered as adaptations of standard image processing techniques, while the identification and the reconstruction of continuous curves is the original contribution specifically developed for optical projection moiré images. The functionality of such an approach is demonstrated for a demanding optical experimental image

Near-optimal pitch of a moiré grating in dynamic visual cryptography

Dynamic visual cryptography (DVC) is a technique for the encryption and decryption of visual secret information. The confidential visual information in DVC is concealed embedding the secret image into the regular moiré grating. The secret can be perceived from the cover image if only the cover image is oscillated according to a predefined law of motion and time-averaging techniques are used. The security of the encryption procedure and the quality of the decrypted image depend on the proper preselection of the pitches of a moiré grating used in the encryption stage. This paper presents the main principles of the determination of near-optimal pair of the pitches of moiré grating as well as graphical schemes and analytical equations in case of harmonic and chaotic oscillations

Information Hiding Based on Statistical Features of Self-Organizing Patterns

A computational technique for the determination of optimal hiding conditions of a digital image in a self-organizing pattern is presented in this paper. Three statistical features of the developing pattern (the Wada index based on the weighted and truncated Shannon entropy, the mean of the brightness of the pattern, and the p-value of the Kolmogorov-Smirnov criterion for the normality testing of the distribution function) are used for that purpose. The transition from the small-scale chaos of the initial conditions to the large-scale chaos of the developed pattern is observed during the evolution of the self-organizing system. Computational experiments are performed with the stripe-type patterns, spot-type patterns, and unstable patterns. It appears that optimal image hiding conditions are secured when the Wada index stabilizes after the initial decline, the mean of the brightness of the pattern remains stable before dropping down significantly below the average, and the p-value indicates that the distribution becomes Gaussian

Image Hiding Scheme Based on the Atrial Fibrillation Model

An image communication scheme based on the atrial fibrillation (AF) model is presented in this paper. Self-organizing patterns produced by the AF model are used to hide and transmit secret visual information. A secret image is encoded into the random matrix of initial cell excitation states in the form of a dot-skeleton representation. Self-organized patterns produced by such initial cell states ensure a secure and efficient transmission of secret visual images. Procedures for digital encoding and decoding of secret images, as well as the sensitivity of the communication scheme to the perturbation of the AF model’s parameters are discussed in the paper