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Search Results: 1 - 10 of 191308 matches for " D. Levicky "
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Robust Digital Watermarking Based on the Log-Polar Mapping
R. Ridzon,D. Levicky
Radioengineering , 2007,
Abstract: The geometrical attacks are still an open problem for many digital watermarking algorithms used in present time. Most of geometrical attacks can be described by using affine transforms. This article deals with digital watermarking in images robust against the affine transformations. The new approach to improve robustness against geometrical attacks is presented. The discrete Fourier transform and log-polar mapping is used for watermark embedding and for watermark detection. Some attacks against the embedded watermarks are performed and the results are given.
Implementations of HVS Models in Digital Image Watermarking
P. Foris,D. Levicky
Radioengineering , 2007,
Abstract: In the paper two possible implementations of Human Visual System (HVS) models in digital watermarking of still images are presented. The first method performs watermark embedding in transform domain of Discrete Cosine Transform (DCT) and the second method is based on Discrete Wavelet Transform (DWT). Both methods use HVS models to select perceptually significant transform coefficients and at the same time to determine the bounds of modification of selected coefficients in watermark embedding process. The HVS models in DCT and DWT domains consist of three parts which exploit various properties of human eye. The first part is the HVS model in DCT (DWT) domain based on three basic properties of human vision: frequency sensitivity, luminance sensitivity and masking effects. The second part is the HVS model based on Region of Interest (ROI). It is composed of contrast thresholds as a function of spatial frequency and eye's eccentricity. The third part is the HVS model based on noise visibility in an image and is described by so called Noise Visibility Function (NVF). Watermark detection is performed without use of original image and watermarks have a form of real number sequences with normal distribution zero mean and unit variance. The robustness of presented perceptual watermarking methods against various types of attacks is also briefly discussed.
Using of Hand Geometry in Biometric Security Systems
P. Varchol,D. Levicky
Radioengineering , 2007,
Abstract: In this paper, biometric security system for access control based on hand geometry is presented. Biometric technologies are becoming the foundation of an extensive array of highly secure identification and personal verification solutions. Experiments show that the physical dimensions of a human hand contain information that is capable to verify the identity of an individual. The database created for our system consists of 408 hand images from 24 people of young ages and different sex. Different pattern recognition techniques have been tested to be used for verification. Achieved experimental results FAR=0,1812% and FRR=14,583% show the possibilities of using this system in environment with medium security level with full acceptance from all users.
Codebook Code Division Multiple Access Image Steganography
D. Levicky,S. Surin
Radioengineering , 2005,
Abstract: In this paper, a new modification of spread spectrum imagesteganography (SSIS) is presented. The proposed modification of SSIShides and recovers a message of substantial length within digital imagewhile maintaining the original image size and dynamic range. Anembedded message can be in the form of text, image, or any otherdigital signal. Our method is based on CDMA SSIS technique. To increasethe information capacity of the stego channel and decrease a distortionof a cover image, a new modification of CDMA using a codebook (in thefollowing referred to as Codebook CDMA (CCDMA)) is suggested.
Pixel Decimation in Block Matching Techniques
P. Radoczi,D. Levicky
Radioengineering , 2000,
Abstract: Block motion estimation using full search algorithm is computationallyextensive. Previously proposed fast algorithms reduce the computationcost by limiting the number of locations searched. In this paper wepresent algorithms for block motion estimation that produce similarperformance to that full search algorithm. The algorithms are based onthe pixel decimation.
Digital Image Watermaking in Color Models Using DCT Transformation
R. Hovancak,D. Levicky
Radioengineering , 2004,
Abstract: In recent years, an access to multimedia data has become much easierdue to the rapid growth of the Internet. While this is usuallyconsidered an improvement of everyday life, it also makes unauthorizedcopying and distributing of multimedia data much easier, thereforepresenting a challenge in the field of copyright protection. Digitalwatermarking, which is inserting copyright information into the data,has been proposed to solve the problem. In this paper two originalwatermarking schemes based on DCT transformation for ownershipverification and authentication of color images were proposed. Somecolor models in process of watermarks embedding and extracting aredescribed too.
Progressive Image Reconstruction Using Morphological Skeleton
D. Levicky,P. Chromek
Radioengineering , 1992,
Abstract: This paper presents the results of a study on use of morphological skeleton to represent, progressive transmission and reconstruction of binary images. For images containing blobs and large areas, the skeleton subsets are much thinner than the original image therefore encoding of skeleton results in lower information rates than other standard coding methods.
Interactive Progressive Image Transmission
E. Matus,D. Levicky
Radioengineering , 1999,
Abstract: In progressive image transmission (PIT) the image is transmitted progressively i.e. the low detail image is transmitted as first followed by transmission of detail signals. In our contribution we consider interactivity in the PIT. For example, the observer could specify image regions of highest interest (ROI). In this case, the image transmission should be optimised with respect to the ROI. The definition of objective criterion for interactive PIT is made in this paper as first. The spatial signal decomposition is derived with respect to this criterion. Wavelet transform of spatial components is used. At the end demonstration of proposed algorithm is made.
Human Visual System Models in Digital Image Watermarking
D. Levicky,P. Foris
Radioengineering , 2004,
Abstract: In this paper some Human Visual System (HVS) models used in digitalimage watermarking are presented. Four different HVS models, whichexploit various properties of human eye, are described. Two of themoperate in transform domain of Discrete Cosine Transform (DCT) andDiscrete Wavelet Transform (DWT). HVS model in DCT domain consists ofJust Noticeable Difference thresholds for corresponding DCT basisfunctions corrected by luminance sensitivity and self- or neighborhoodcontrast masking. HVS model in DWT domain is based on different HVSsensitivity in various DWT subbands. The third presented HVS model iscomposed of contrast thresholds as a function of spatial frequency andeye's eccentricity. We present also a way of combining these threebasic models to get better tradeoff between conflicting requirements ofdigital watermarks. The fourth HVS model is based on noise visibilityin an image and is described by so called Noise Visibility Function(NVF). The possible ways of exploiting of the described HVS models indigital image watermarking are also briefly discussed.
Adaptive Digital Image Watermarking Based on Combination of HVS Models
P. Foris,D. Levicky
Radioengineering , 2009,
Abstract: In this paper two new blind adaptive digital watermarking methods of color images are presented. The adaptability is based on perceptual watermarking which exploits Human Visual System (HVS) models. The first method performs watermark embedding in transform domain of DCT and the second method is based on DWT. Watermark is embedded into transform domain of a chosen color image component in a selected color space. Both methods use a combination of HVS models to select perceptually significant transform coefficients and at the same time to determine the bounds of modification of selected coefficients. The final HVS model consists of three parts. The first part is the HVS model in DCT (DWT) domain. The second part is the HVS model based on Region of Interest and finally the third part is the HVS model based on Noise Visibility Function. Watermark has a form of a real number sequence with normal distribution.
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