Image watermarking using spread spectrum technique in log-2-spatio domain

Protection of copyright is a crucial issue in the data transmission and distribution. Considering the fact that there are different types of information available for misuse and manipulation by all the internet users it is necessary to establish the rules for copyright protection of a certain content. In this paper, special attention is given to the technical aspects of copyright protection. We took a digital image and a digital watermark into consideration. The original image has undergone a discrete wavelet transformation. Then, spread spectrum techniques were applied to the watermark. Digital watermark is then embedded into the original image. The aim of the paper is to present the comparison of results obtained using two different spread spectrum techniques in image watermarking.

After a watermarked image is printed, copied several times and scanned, the watermark usually cannot be extracted rightly, as well as distorted by noise. In this paper, a spread spectrum technique was introduced to image watermarking which can be applied to print and generation copy. The watermarking message is modulated by the key-dependent pseudo-random sequences to produce a spread spectrum signal. The watermark is embedded into the cover image by modifying the gray value of each pixel. The cover image is not needed when the watermark is detected. The watermark is estimated exploiting the properties of HVS(Human Visual System) and extracted through the same key-dependent 2D sequences. Experimental results show that the scheme can resist print, generation copy and scan process.

Digital watermarking has been proposed as a method for discouragement of illegal copying and distribution of copyrighted material. Currently proposed algorithms of digital watermarking in the context of the video are robust against unintentional attacks, but many of them do not protect enough against malicious attacks. This paper presents a new video watermarking system with improved robustness, which is based on spread spectrum technique. Finally, we also present results, which verify the enhanced robustness of proposed system against malicious and non-malicious attacks.

With the growth of multimedia systems in distributed environments, the research of multimedia security as well as multimedia copyright protection becomes an important issue. As a potential and effective way to solve this problem, digital watermarking becomes a very active research area of signal and information processing. Many watermark algorithms have been proposed to address this issue of ownership identification. Discrete Cosine Transform (DCT) based spread-spectrum watermarking is one of the famous techniques. Another possible domain for watermark embedding is the wavelet domain. One of the many advantages over the Discrete Wavelet Transform (DWT) is that more accurately model aspects of the human visual system (HVS). In this paper a proposed algorithm is defined based on the combination between the benefits provides by using wavelet domain and profits of Code division multiple access (CDMA) spread-spectrum technique. A pseudo-random sequence (key) that related to hidden message is embedded into the significant DWT coefficients of a cover image to produce a watermarked image. Experimental results demonstrate that the proposed algorithm is perceptual invisible and robust against many attacks such as lossy image compression and Additive White Gaussian Noise (AWGN). Keywords: digital watermark, wavelet transform, CDMA technique.

To analyze different control-system limitations on the measured dose distributions in low-dose regions of simplified intensity fields with an electronic portal imaging device to ascertain the optimal settings for the control-system limitations in the planning system. The authors created one field with an "optimal fluence" of intensity 1.0 (full dose) and one field with intensity 0.0 (no dose) in the central part of the field. The influence of different dose rates (DRs) and maximum leaf speeds (LS) on the calculated and measured dose and dose profiles were analyzed. Good agreement between calculated and measured dose in the case of a field of intensity 1.0 was found. For the field with intensity 0.0, the measured dose was 20-60% lower than the dose calculated by the "actual fluence". The results were found dependent on the DR and LS. The overestimation in regions of optimal intensity 0.0 by the planning system cannot be resolved by the user. Taking the measured dose in the region of desired intensity 1.0 and other technical limitations (like beam hold interrupts or spikes in the cross and longitudinal profiles) into consideration, the application of an LS of 2.5 cm/s and a DR of 500 MU/min is recommended in order to minimize radiation dose applied to organs at risk, which are located in regions of low intensity, like, for example, the spinal cord.

There is able to be critical performance impairment because satellite digital broadcasting system such as DVB-S2 is sensitive to heavy rain environment. This feature of the satellite channel does not only make users be able to give inconvenient broadcasting service but they cannot see the service. Spread spectrum technique is the new proposal which can overcome those problems that are generated due to rain attenuation. Applying spread spectrum to DVB-S2 system, we examine how effective the technique is in the broadcast system. Assuming that signal power and channel bandwidth are same in the proposed system and the original system, the reason why spread spectrum technique is effective in heavy rain environment will be demonstrated. And using computer simulation, the performance improvement is shown.

The transition from analog technologies to digital technologies has increased the ever-growing concern for protection and authentication of digital content and data. Owners of digital content of any type are seeking and exploring new technologies for the protection of copyrighted multimedia content. Multimedia protection has become an issue in recent years, and to deal with this issue, researchers are continuously searching for and exploring new effective and efficient technologies. This thesis study has been prepared in order to increase the invisibility and durability of invisible watermarking by using the multilayer Discrete Wavelet Transform (DWT) in the frequency plane and embedding two marks into an image for the purpose of authentication and copyright when digital content travels through an unsecured channel. A novel watermarking algorithm has been proposed based on five active positions and on using two marks. In addition to the extraction process, watermarking images will be subjected to a set of attack tests. The evaluation criteria have been the bases of assessing the value of SNR, PNSR, MAE and RMSE for both the watermarking images and the watermarking images after attacks, followed by the invisibility of the watermarking being measured before and after the attacks. Our lab results show high robustness and high quality images obtaining value for both SNR and PNSR.

A general method is described to take into account the multiple scattering effect in a small‐angle light scattering from thin polymer films. It is seen that multiple scattering tends to make the scattering envelope more diffuse, reducing the intensity in the high intensity regions and increasing it in the low intensity regions. The method is applied here to a spherulitic system, but it is valid for any other system where the principal scattering is in the forward direction.

According to singular optics, the phase and intensity that characterize structured electromagnetic beams can be understood in terms of concepts that involve subspaces where they or their derivatives exhibit a particular behavior, such as giving rise to extreme values or not being well defined. Caustics are a paradigmatic example of the former, while helical dislocation lines exemplify the latter. In this work the interrelation of the morphology of caustics and the morphology of dislocation lines is theoretically studied. The analysis for highly structured beams requires an efficient methodology that allows the identification of optical vortices, their topological charge, and the helical dislocation lines they belong to. Such a methodology is introduced and applied to paraxial elliptic umbilic beams and nonparaxial Airy symmetric three-dimensional beams. Nonparaxial beams exhibit caustic surfaces that delimit regions with a finite volume and different intensity average. It is shown that in the high intensity region so defined, the dislocation lines play the role of an internal skeleton, i.e., an endoskeleton, of the beam. The exoskeleton created in the low intensity regions shows subtle and interesting features that complement those of the endoskeleton; the caustics that delimit low intensity regions have a strong influence on the morphology of the exoskeleton.

Quiescent filaments appear as absorption features on the solar disk when observed in chromospheric lines and at continuum wavelengths in the millimeter (mm) range. Active region (AR) filaments are their small-scale, low-altitude analogues, but they could not be resolved in previous mm observations. This spectral diagnostic can provide insight into the details of the formation and physical properties of their fine threads, which are still not fully understood. Here, we shed light on the thermal structure of an AR filament using high-resolution brightness temperature (Tb) maps taken with ALMA Band 6 complemented by simultaneous IRIS near-UV spectra, Hinode/SOT photospheric magnetograms, and SDO/AIA extreme-UV images. Some of the dark threads visible in the AIA 304 Å passband and in the core of Mg ii resonance lines have dark (Tb < 5,000 K) counterparts in the 1.25 mm maps, but their visibility significantly varies across the filament spine and in time. These opacity changes are possibly related to variations in temperature and electron density in filament fine structures. The coolest Tb values (< 5,000 K) coincide with regions of low integrated intensity in the Mg ii h and k lines. ALMA Band 3 maps taken after the Band 6 ones do not clearly show the filament structure, contrary to the expectation that the contrast should increase at longer wavelengths based on previous observations of quiescent filaments. The ALMA maps are not consistent with isothermal conditions, but the temporal evolution of the filament may partly account for this.

The authors report two cases of malignant peripheral nerve sheath tumors arising from the vagus nerve in the mediastinum in patients who had no stigmata of neurofibromatosis (von Recklinghausen's disease). Computed tomography showed homogeneous soft tissue masses, with minimal calcification seen in one patient. T2-weighted magnetic resonance images showed regions of low signal intensity caused by a dense cellular population.

The South Atlantic Magnetic Anomaly (SAMA) has been studied since the beginning of the sixties. This region of low field intensity in the South Adantic near Brazil is known to have important consequences in radiationbelt physics “e.g., Pinto and Gonzalez, 1986”. This feature of the field can be explained by the concept of an eccentric dipole. This concept, specified by the dipole and quadrupole terms of the multipole expansion of the geomagnetic field, account for about 90% of the surface field “Parkinson, 1983”.

We describe new techniques to measure the near-infrared extinction law and to place limits on the pre–main-sequence stellar population of a dark cloud. We analyze JHK imaging data for the central 1 deg2 of the ρ Ophiuchi cloud core and show that nearly all stars projected onto regions of low CS intensity, ICS ≤ 10 K km s-1, are background stars. Most sources at larger CS intensities lie within cloud material. We use the background stars to derive the slope of the near-IR extinction law, EJ - H/EH - K = 1.57 ± 0.03. This result is consistent with previous extinction laws but has a factor of 2–3 smaller uncertainty. The new ρ Oph extinction law yields strong constraints on the number of previously undiscovered pre–main-sequence stars in the cloud, 46 ± 11, and the number of previously undiscovered young stars with near-IR excesses, 15 ± 4. Neither limit exceeds the number of known pre–main-sequence stars in the cloud, ∼100. Thus, current samples of pre–main-sequence stars are reasonably complete for K ≤ 14.

Transient myometrial contraction as a physiological phenomenon may simulate pathological conditions, such as a focal or diffuse adenomyosis. Clinicians should be aware of the potential presence of this phenomenon and imaging should be repeated after a suitable interval when the nature of a bulge or a region of low intensity in the myometrium is in doubt. In this paper, we report a transient myometrial contraction that mimics an adenomyosis, but disappears in repeated series.

Purpose: Quality assurance (QA) of dose homogeneity in total skin electron therapy (TSET) is challenging since each patient is positioned in six standing poses with two beam angles. Our study tested the feasibility of a unique approach for TSET QA through computational display of the cumulative dose, constructed and synthesized by computer animation methods. Approach: Dose distributions from Cherenkov emission images were projected onto a scanned 3D body model. Topographically mapped surfaces of the patient were recorded in each of six different delivery positions, while a Cherenkov camera acquired images. Computer animation methods allowed a fitted 3D human body model of the patient to be created with deformation of the limbs and torso to each position. A two-dimensional skin map was extracted from the 3D model of the full surface of the patient. This allowed the dose mapping to be additively accumulated independent of body position, with the total dose summed in a 2D map and reinterpreted on the 3D body display. Results: For the body model, the mean Hausdorff error distance was below 2cm, setting the spatial accuracy limit. The dose distribution over the patient's 3D model generally matched the Cherenkov/dose images. The dose distribution mapping was estimated to be near 1.5cm accuracy based upon a phantom study. The body model must most closely match at the edges of the mesh to ensure that high dose gradients are not projected onto the wrong location. Otherwise 2 to 3cm level errors in positioning in the mesh do not appear to cause larger than 5% dose errors. The cumulative dose images showed regions of overlap laterally and regions of low intensity in the posterior arms. Conclusions: The proposed modeling and animation can be used to visualize and analyze the accumulated dose in TSET via display of the summed dose/Cherenkov images on a single body surface.