System In Spatial Domain Research Articles

A new digital steganography system based on hiding online signature within document image data in YUV color space

Due to the progression in computer technology and fast growth of interchange of data, Steganographyis becoming the best solution for providing greater security for sensitive document images which are uncontrolled across the internet. In this paper, we introduce a new signature steganography system for color document images in YUV color space based on the stego key and the Beta elliptic modeling. Firstly, the cover color document image is transformed into YUV from RGB space. Afterward, the embedding positions are identified based on the potential feature by using the Binary Robust Invariant Scalable Keypoints (BRISK) detector. In the next step, we decide the channel in which a Beta elliptic signature bits will be hidden on the basis of bitxor operation of Y channel’s LSB and the bits of stego key. Finally, the proposed system hides the Beta elliptic signature bits adaptively in U or V channel. It could be perceived from the results of experimentation that by the use of the proposed system, the embedded data is detectable even in the existence of common image processing distortion, as well the proposed steganography system in spatial domain has demonstrated to be robust and outperform the related works in term of the measurements image quality.

A Grayscale Image Fragile Watermark Authentication System in Spatial-Domain

This study deals with devising and implementing a novel technique for image authentication and secured message transmission based on hiding large volume of data into gray scale images. A grayscale image fragile watermark authentication system in spatial-domain is proposed. First it preprocesses the watermark image and resizes it to a quarter of the size of the original image. Then, it generates a random key matrix K and 128bit message authentication code from the original image. It replaces the 128bit message authentication code for the former 128bit of K to obtain a new key matrix KH. Then, it calculates the embedded position P=KHi xor (b7,b6,b5.b4) i MOD 3. b7,b6,b5,b4 are the high 4 bits of the original images pixel. It embeds the watermark image according to P value to the lower 4 bits of the original images pixel. The system is made in experiment. The result shows the system has good imperceptibility.

Position‐dependent disturbance rejection using spatial‐based adaptive feedback linearization repetitive control

AbstractIn this paper, we propose a new design of spatial‐based repetitive control for a class of rotary motion systems operating at variable speeds. The open‐loop system in spatial domain is obtained by reformulating a nonlinear time‐invariant system with respect to angular displacement. A two‐degree‐of‐freedom control structure (comprising two control modules) is then proposed to robustly stabilize the open‐loop system and improve the tracking performance. The first control module applies adaptive feedback linearization with projected parametric update and concentrates on robust stabilization of the closed‐loop system. The second control module introduces a spatial‐based repetitive controller cascaded with a loop‐shaping filter, which not only further reduces the tracking error, but also improves parametric adaptation. The overall control system is robust to model uncertainties of the system and capable of rejecting position‐dependent disturbances under varying process speeds. Stability proof for the overall system is given. A design example with simulation is provided to demonstrate the applicability of the proposed design. Copyright © 2008 John Wiley & Sons, Ltd.

Propagation of elliptical cosh-Gaussian beams in a misaligned optical system

On the basis of the generalized diffraction integral formula for misaligned optical systems in spatial domain, an analytical propagation expression for the elliptical cosh-Gaussian beam (EChGB) passing through misaligned optical systems is obtained by using vector integration. Some numerical simulations are illustrated for the propagation properties of an EChGB through a misaligned optical transforming system with a misaligned thin lens. As an application example, the propagation of off-axial EChGBs passing through misaligned optical systems is studied, and further extensions are also pointed out.

Propagation of partially coherent twisted anisotropic Gaussian–Schell model beams through misaligned optical systems

The generalized diffraction integral formulae for partially coherent beams through misaligned optical systems are derived in both spatial and spatial-frequency domain. Based on these formulae, the analytical propagation formulae for partially coherent twisted anisotropic Gaussian–Schell model (GSM) beams through misaligned optical systems are derived. The derived formulae provide a powerful and convenient tool for treating the propagation and transformation of partially coherent twisted anisotropic GSM beams through misaligned optical systems in spatial domain and spatial-frequency domain. As an application example, the intensity distribution properties of partially coherent twisted GSM beams through a misaligned thin lens are studied.

Propagation of elliptical Gaussian beam through misaligned optical systems in spatial domain and spatial-frequency domain

The propagation formulae of elliptical Gaussian beam through misaligned optical systems in spatial domain and spatial-frequency domain are investigated analytically by using tensor method. The derived formulae provide a powerful tool for treating the propagation and transformation of elliptical Gaussian beam through misaligned optical systems. As an application example, the propagation properties of elliptical Gaussian beam through a misaligned thin lens are illustrated.

Generalized diffraction integral formulae for misaligned optical systems described by fractional Fourier transforms

Summary It is shown that, under some conditions, the generalized diffraction integral formula for any misaligned optical system in spatial-domain could be described by the fractional Fourier transform. On the other hand, the generalized diffraction integral formula for angular spectra through any misaligned optical system in spatial-frequency domain could also be described by the fractional Fourier transform. A practical optical system with a misaligned lens is given to illustrate its application.