Journal articles: 'Transformée de cosinus discrète'

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Smigiel, E., A. Knoll, N. Broll, and A. Cornet. "Modèles direct et inverse de la réflectométrie non spéculaire par transformée en cosinus discrète." Le Journal de Physique IV 10, PR10 (September 2000): Pr10–237—Pr10–243. http://dx.doi.org/10.1051/jp4:20001026.

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Amiot, Emmanuel. "Gammes bien réparties et transformée de Fourier discrète." Mathématiques et sciences humaines, no. 178 (July 1, 2007): 95–118. http://dx.doi.org/10.4000/msh.4272.

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Pissondes, Jean-Claude. "Une représentation 3D de la Transformée de Fourier Discrète." J3eA 16 (2017): 0001. http://dx.doi.org/10.1051/j3ea/2017001.

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O. Ahmed, Hawkar. "Race Classification from Face Images Using Fast Fourier Transform and Discrete Cosine Transform." Journal of Zankoy Sulaimani - Part A 22, no. 2 (December 20, 2020): 149–56. http://dx.doi.org/10.17656/jzs.10816.

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Park, Do-Young, and Hoon Yoo. "CT Reconstruction using Discrete Cosine Transform with non-zero DC Components." Transactions of The Korean Institute of Electrical Engineers 63, no. 7 (July 1, 2014): 1001–7. http://dx.doi.org/10.5370/kiee.2014.63.7.1001.

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Ahmad, Faraidoon H., and Aree A. Mohammed. "Hybrid Wavelet and Discrete Cosine Transform Methods for Ethnicity Identification." Journal of Zankoy Sulaimani - Part A 17, no. 1 (December 10, 2014): 121–30. http://dx.doi.org/10.17656/jzs.10366.

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Pinhabel Marafão, Fernando, Paolo Mattavelli, Simone Buso, and Sigmar Maurer Deckmann. "Repetitive-based Control For Selective Active Filters Using Discrete Cosine Transform." Eletrônica de Potência 9, no. 1 (June 1, 2004): 29–36. http://dx.doi.org/10.18618/rep.2004.1.029036.

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Pinhabel Marafão, Fernando, Paolo Mattavelli, Simone Buso, and Sigmar Maurer Deckmann. "Repetitive-based Control For Selective Active Filters Using Discrete Cosine Transform." Eletrônica de Potência 9, no. 1 (June 1, 2004): 29–36. http://dx.doi.org/10.18618/rep.2005.1.029036.

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Tyagi, Surya Kant. "Face Recognition Using Discrete Cosine Transform and Nearest Neighbor Discriminant Analysis." International Journal of Engineering and Technology 4, no. 3 (2012): 311–14. http://dx.doi.org/10.7763/ijet.2012.v4.372.

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Hayati, Raisah, and Rahmadi Kurnia. "Simulasi Unjuk Kerja Discrete Wavelet Transform (DWT) dan Discrete Cosine Transform (DCT) untuk Pengolahan Sinyal Radar di Daerah yang Ber-Noise Tinggi." Jurnal Nasional Teknik Elektro 3, no. 1 (March 1, 2014): 32–43. http://dx.doi.org/10.20449/jnte.v3i1.53.

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Jang, Ju-wook, Chang-hyeon Lim, Ronald Scrofano, and Viktor K. Prasanna. "Energy-Efficient Discrete Cosine Transform on FPGAs." KIPS Transactions:PartA 12A, no. 4 (August 1, 2005): 313–20. http://dx.doi.org/10.3745/kipsta.2005.12a.4.313.

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KARHAN, Mustafa. "Dielektrik Malzemelerin Yüzeyleri için Islanabilirlik ve Buharlaşma Hızının Analizine Yönelik Ayrık Kosinüs Dönüşümü Tabanlı Bir Yaklaşım." Gazi Journal of Engineering Sciences 7, no. 2 (August 30, 2021): 160–68. http://dx.doi.org/10.30855/gmbd.2021.02.09.

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Qingmin Zhao, Qingmin Zhao, Xianzhe Luo Xianzhe Luo, Nanrun Zhou Nanrun Zhou, and Jianhua Wu Jianhua Wu. "Multiple and color images compression-encryption schemes with balanced qualities based on the multiple-order discrete fractional cosine transform." Chinese Optics Letters 10, s1 (2012): S11006–311010. http://dx.doi.org/10.3788/col201210.s11006.

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Dayanand, I. Edwin, and R. K. Selva Kumar. "Discrete Cosine Transformer Based Visual Secret Sharing With Chaos Visual Cryptography." International Journal of Multimedia and Ubiquitous Engineering 10, no. 10 (October 31, 2015): 99–110. http://dx.doi.org/10.14257/ijmue.2015.10.10.11.

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Ito, Izumi. "A New Pseudo-Spectral Method Using the Discrete Cosine Transform." Journal of Imaging 6, no. 4 (March 28, 2020): 15. http://dx.doi.org/10.3390/jimaging6040015.

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The pseudo-spectral (PS) method on the basis of the Fourier transform is a numerical method for estimating derivatives. Generally, the discrete Fourier transform (DFT) is used when implementing the PS method. However, when the values on both sides of the sequences differ significantly, oscillatory approximations around both sides appear due to the periodicity resulting from the DFT. To address this problem, we propose a new PS method based on symmetric extension. We mathematically derive the proposed method using the discrete cosine transform (DCT) in the forward transform from the relation between DFT and DCT. DCT allows a sequence to function as a symmetrically extended sequence and estimates derivatives in the transformed domain. The superior performance of the proposed method is demonstrated through image interpolation. Potential applications of the proposed method are numerical simulations using the Fourier based PS method in many fields such as fluid dynamics, meteorology, and geophysics.

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Saeed, Umer. "Sine–cosine wavelets operational matrix method for fractional nonlinear differential equation." International Journal of Wavelets, Multiresolution and Information Processing 17, no. 04 (July 2019): 1950026. http://dx.doi.org/10.1142/s0219691319500267.

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In this paper, we present a solution method for fractional nonlinear ordinary differential equations. We propose a method by utilizing the sine–cosine wavelets (SCWs) in conjunction with quasilinearization technique. The fractional nonlinear differential equations are transformed into a system of discrete fractional differential equations by quasilinearization technique. The operational matrices of fractional order integration for SCW are derived and utilized to transform the obtained discrete system into systems of algebraic equations and the solutions of algebraic systems lead to the solution of fractional nonlinear differential equations. Convergence analysis and procedure of implementation for the proposed method are also considered. To illustrate the reliability and accuracy of the method, we tested the method on fractional nonlinear Lane–Emden type equation and temperature distribution equation.

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Masaki, T., Y. Morimoto, T. Onoye, and I. Shirakawa. "VLSI implementation of inverse discrete cosine transformer and motion compensator for MPEG2 HDTV video decoding." IEEE Transactions on Circuits and Systems for Video Technology 5, no. 5 (1995): 387–95. http://dx.doi.org/10.1109/76.473552.

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Moussa, Mourad, Maha Hmila, and Ali Douik. "Face recognition using fractional coefficients and discrete cosine transform tool." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 1 (February 1, 2021): 892. http://dx.doi.org/10.11591/ijece.v11i1.pp892-899.

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Face recognition is a computer vision application based on biometric information for automatic person identification or verification from image sequence or a video frame. In this context DCT is the easy technique to determine significant parameters. Until now the main object is selection of the coefficients to obtain the best recognition. Many techniques rely on premasking windows to discard the high and low coefficients to enhance performance. However, the problem resides in the shape and size of premask. To improve discriminator ability in discrete cosine transform domain, we used fractional coefficients of the transformed images with discrete cosine transform to limit the coefficients area for a better performance system. Then from the selected bands, we use the discrimination power analysis to search for the coefficients having the highest power to discriminate different classes from each other. Feature selection algorithm is a key issue in all pattern recognition system, in fact this algorithm is utilized to define features vector among several ones, where these features are selected according a specified discrimination criterion. Many classifiers are used to evaluate our approach like, support vector machine and random forests. The proposed approach is validated with Yale and ORL Face databases. Experimental results prove the sufficiency of this method in face and facial expression recognition field.

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Zhang, Shun, Tie-gang Gao, and Fu-sheng Yang. "A High Capacity Reversible Data Hiding Scheme Based on Multi-Level Integer DWT and Histogram Modification." International Journal of Digital Crime and Forensics 6, no. 1 (January 2014): 51–64. http://dx.doi.org/10.4018/ijdcf.2014010104.

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A reversible data hiding scheme based on integer DWT and histogram modification is proposed. In the scheme, the cover media is firstly transformed by Integer DWT (Discrete Wavelet Transformation); then information is embedded through the modification of histograms of the middle and high frequency sub-bands of the DWT coefficients. In order to increase the embedding capacity, a multi-level scheme is proposed, which achieved both high embedding capacity and reversibility. Extensive experimental results have shown that the proposed scheme achieves both higher embedding capacity and lower distortion than spatial domain histogram modification based schemes; and it achieved better performance than integer DCT (Discrete Cosine Transformation) based histogram modification scheme.

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HEGDE, VEENA N., RAVISHANKAR DEEKSHIT, and P. S. SATYANARAYANA. "DCT-BASED VARIABLE STEP SIZE GRIFFITHS' LMS ALGORITHM FOR RANDOM NOISE CANCELLATION IN ECGs." Journal of Mechanics in Medicine and Biology 12, no. 05 (December 2012): 1250025. http://dx.doi.org/10.1142/s021951941250025x.

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This paper presents a new random noise cancellation technique for cancelling muscle artifact effects from ECG using ALE in the transformed domain. For this a transform domain variable step size griffith least mean square (TVGLMS) algorithm is proposed. The technique is based on the adaptation of the gradient of the error surface. The method frees both the step size and the gradient from observation noise and reduces the gradient mis-adjustment error. The sluggishness introduced due to the averaging of the gradient in the time domain is overcome by the transformed domain approach. The proposed algorithm uses a discrete cosine transform (DCT)-based signal decomposition due to its improved frequency resolution compared to a discrete Fourier transform (DFT). Furthermore, as the data used symmetrical, DCT usage results in low leakage (bias and variance). The performance of the proposed method has been tested on ECG signals combined with WGN, extracted from MIT database, and compared with several existing techniques like LMS, NLMS, and VGLMS.

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Fu, Yong Gang. "A Print-Scan Resilient Image Watermarking Scheme Based on Radon Transform." Applied Mechanics and Materials 687-691 (November 2014): 3812–17. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.3812.

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In this paper, a print-scan resilient image watermarking scheme based on Radon transform and DCT(discrete cosine transform) is proposed. The watermark is preprocessed with a chaotic sequence, then the host image is transformed to frequency domain by block DCT. The preprocessed watermark is adaptively embedded into the transform domain coefficients by modulating the relationship between neighbor coefficients. The watermark detection process is accomplished without referring to the original image. Simulation results show good robustness against several attacks, such Jpeg compression, cropping, filtering and so on.

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Chang, Ko Chin. "Multi-Focus Image Fusion Using Local Energy Pattern." Applied Mechanics and Materials 145 (December 2011): 119–23. http://dx.doi.org/10.4028/www.scientific.net/amm.145.119.

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For general image capture device, it is difficult to obtain an image with every object in focus. To solve the fusion issue of multiple same view point images with different focal settings, a novel image fusion algorithm based on local energy pattern (LGP) is proposed in this paper. Firstly, each focus images is decomposed using discrete wavelet transform (DWT) separately. Secondly, to calculate LGP with the corresponding pixel and its surrounding pixels, then use LGP to compute the new coefficient of the pixel from each transformed images with our proposed weighted fusing rules. The rules use different operations in low-bands coefficients and high-bands coefficients. Finally, the generated image is reconstructed from the new subband coefficients. Moreover, the reconstructed image can represent more detailed for the obtained scene. Experimental results demonstrate that our scheme performs better than the traditional discrete cosine transform (DCT) and discrete wavelet transform (DWT) method in both visual perception and quantitative analysis.

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Aggarwal, Vibha, and Manjeet Singh Patterh. "PERFORMANCE ANALYSIS OF NONLINEAR TRANSFORMATIONAL ECG COMPRESSION METHOD." Biomedical Engineering: Applications, Basis and Communications 21, no. 04 (August 2009): 245–51. http://dx.doi.org/10.4015/s1016237209001350.

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This paper presents and analyzes nonlinear transform-based method electrocardiogram (ECG) compression. The procedure used is similar to that used in linear transform-based method. The ECG signal is first transformed using (i) linear transform: discrete cosine transforms (DCT), Laplacian pyramid (LP), wavelet transform (WT) and it is transformed using (ii) nonlinear transform: essentially nonoscillatory cell average (ENOCA). The transformed coefficients (TC) are thresholded using the bisection algorithm in order to match the predefined user-specified percentage root mean square difference (PRD) within the tolerance. Then, the binary lookup table is made to store the position map for zero and nonzero coefficients (NZCs). The NZCs are quantized by Max–Lloyd quantizer followed by arithmetic coding. Lookup table is encoded by Huffman coding. The results are presented on different ECG signals of varying characteristics. The results show that nonlinear transform (ENOCA) gives better performance at high PRD where as at low PRD, DCT performs better.

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Iwut, Iwan, Gelar Budiman, and Ledya Novamizanti. "Optimization of Discrete Cosine Transform-Based Image Watermarking by Genetics Algorithm." Indonesian Journal of Electrical Engineering and Computer Science 4, no. 1 (October 1, 2016): 91. http://dx.doi.org/10.11591/ijeecs.v4.i1.pp91-103.

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data in an image file is needed by its owner to set his ownership in a logo as a watermark embedded in the image file. Hiding the logo in the image was done in several methods. One of the method is domain transform using 2D-DCT in which data is embedded in frequency domain of the image. First, the host RGB image is converted to certain color space. The available and chosen color spaces are RGB, YCbCr or NTSC. The layer in which the watermark is embedded also can be selected. The available choices are 1st layer, 2nd layer, 3rd layer, 1st & 2nd layer, 2nd & 3rd layer, 1st & 3rd layer and all layers. After the selected layer of image in certain color space is transformed in block based to frequency domain by DCT, one bit watermark is embedded on the AC coefficient of each block such a way that the bit is represented by specific value called delta in a zigzag and vary length of pixel. The vary parameters optimized by Genetics Algorithm are selected color space, selected layer, block size, length of pixel to be embedded by one bit watermark, and delta. Bit “1” is represented by +delta, and bit “0” is represented by –delta in vary length of pixel after zigzag. The simulation result performs that GA is useful to search the value of parameter that produces controllable the combination between robustness, invisibility and capacity. Thus, GA improves the method by determining the exact value of parameter achieving BER, PSNR and payload.

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Zadeh, Pooneh Bagheri, Akbar Sheikh Akbari, and Tom Buggy. "DCT image codec using variance of sub-regions." Open Computer Science 5, no. 1 (August 11, 2015): 13–21. http://dx.doi.org/10.1515/comp-2015-0003.

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AbstractThis paper presents a novel variance of subregions and discrete cosine transform based image-coding scheme. The proposed encoder divides the input image into a number of non-overlapping blocks. The coefficients in each block are then transformed into their spatial frequencies using a discrete cosine transform. Coefficients with the same spatial frequency index at different blocks are put together generating a number of matrices, where each matrix contains coefficients of a particular spatial frequency index. The matrix containing DC coefficients is losslessly coded to preserve its visually important information. Matrices containing high frequency coefficients are coded using a variance of sub-regions based encoding algorithm proposed in this paper. Perceptual weights are used to regulate the threshold value required in the coding process of the high frequency matrices. An extension of the system to the progressive image transmission is also developed. The proposed coding scheme, JPEG and JPEG2000were applied to a number of test images. Results show that the proposed coding scheme outperforms JPEG and JPEG2000 subjectively and objectively at low compression ratios. Results also indicate that the proposed codec decoded images exhibit superior subjective quality at high compression ratios compared to that of JPEG, while offering satisfactory results to that of JPEG2000.

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Novamizanti, Ledya, Ida Wahidah, and Ni Wardana. "A Robust Medical Images Watermarking Using FDCuT-DCT-SVD." International Journal of Intelligent Engineering and Systems 13, no. 6 (December 31, 2020): 266–78. http://dx.doi.org/10.22266/ijies2020.1231.24.

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One way to prevent image duplication is by applying watermarking techniques. In this work, the watermarking process is applied to medical images using the Fast Discrete Curvelet Transforms (FDCuT), Discrete Cosine Transform (DCT), and Singular Value Decomposition (SVD) methods. The medical image of the host is transformed using FDCuT so that three subbands are obtained. High Frequency (HF) subband selected for DCT and SVD applications. Meanwhile, SVD was also applied to the watermark image. The singular value on the host image is exchanged with the singular value on the watermark. Insertion of tears by exchanging singular values does not cause the quality of medical images to decrease significantly. The experimental results prove that the proposed FDCuT-DCT-SVD algorithm produces good imperceptibility. The proposed algorithm is also resistant to various types of attacks, including JPEG compression, noise enhancement attacks, filtering attacks, and other common attacks.

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Latreche, Boubakeur, Slami Saadi, Mecheri Kious, and Ali Benziane. "A novel hybrid image fusion method based on integer lifting wavelet and discrete cosine transformer for visual sensor networks." Multimedia Tools and Applications 78, no. 8 (September 17, 2018): 10865–87. http://dx.doi.org/10.1007/s11042-018-6676-z.

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Roy, Soumitra, and Arup Kumar Pal. "An indirect watermark hiding in discrete cosine transform–singular value decomposition domain for copyright protection." Royal Society Open Science 4, no. 6 (June 2017): 170326. http://dx.doi.org/10.1098/rsos.170326.

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Digital image watermarking has emerged as a promising solution for copyright protection. In this paper, a discrete cosine transform (DCT) and singular value decomposition (SVD) based hybrid robust image watermarking method using Arnold scrambling is proposed and simulated to protect the copyright of natural images. In this proposed scheme, before embedding, watermark is scrambled with Arnold scrambling. Then, the greyscale cover image and encrypted watermark logo are decomposed into non-overlapping blocks and subsequently some selected image blocks are transformed into the DCT domain for inserting the watermark blocks permanently. For better imperceptibility and effectiveness, in this proposed algorithm, watermark image blocks are embedded into singular values of selected blocks by multiplying with a feasible scaling factor. Simulation result demonstrates that robustness is achieved by recovering satisfactory watermark data from the reconstructed cover image after applying common geometric transformation attacks (such as rotation, flip operation, cropping, scaling, shearing and deletion of lines or columns operation), common enhancement technique attacks (such as low-pass filtering, histogram equalization, sharpening, gamma correction, noise addition) and jpeg compression attacks.

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Belilita, Sarra, Nourredine Amardjia, Tewfik Bekkouche, and Imen Nouioua. "Combining SVD-DCT Image Watermarking Scheme Based on Perona-Malik Diffusion." Elektronika ir Elektrotechnika 25, no. 4 (August 7, 2019): 68–74. http://dx.doi.org/10.5755/j01.eie.25.4.23973.

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In this paper, we propose an efficient image watermarking scheme based on combining Singular Value Decomposition (SVD) and Discrete Cosine Transform (DCT) transforms. The main idea consists of exploiting results obtained by the well-known Perona-Malik diffusion applied in image de-noising in watermarking domain by selecting significant blocks to embed a binary logo watermark. After applying the DCT on the selected blocks, the SVD is performed on each of these transformed blocks to modify a few numbers of its U matrix elements according to some defined conditions. Computer simulation and experimental results prove the efficiency of our proposed method against image processing attacks and outperform several previous schemes in terms of imperceptibility and robustness.

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Syvokobylenko, V. F., and V. A. Lysenko. "APPLICATION OF WAVELET TRANSFORM FOR PHASE-TO-GROUND FAULT PROTECTION IN MEDIUM VOLTAGE ELECTRICAL NETWORKS." Tekhnichna Elektrodynamika 2021, no. 4 (June 17, 2021): 55–62. http://dx.doi.org/10.15407/techned2021.04.055.

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For electrical networks with voltage of 6-35 kV with a compensated, isolated or resistor-grounded neutral, a phase-to-ground protection has been developed, in which, based on the results of the time-frequency wavelet transform of zero-sequence currents, voltages and their derivatives, using the obtained analytical expression, the total reactive power wavelet for different frequencies is determined. It is shown that at the initial moment of a phase-to-ground fault on the damaged feeder the power is always positive, and on the undamaged feeder it is negative, regardless of the operating mode of the neutral. Wavelet transform coefficients are found by convolution of discrete values of measured signals with sine-cosine signals of the Morlet mother function. The time-reversed sequence of these signals is obtained using a matrix for which the rules for its formation are stated. An excess of the zero phase sequence voltage amplitude of the set value is used as a starting protection element. With the help of a mathematical model of the network, studies of the behavior of protection in case of blind and arc phase-to-ground faults at various degrees of compensation of capacitive currents, at various voltage values at the moment of the short circuit have been carried out. In all modes, a reliable protection operation is obtained, the sensitivity of which is an order of magnitude higher than the protection based on Fourier transforms. Positive results of testing a protection sample implemented on a microprocessor-based element base at a laboratory stand are obtained. References 20, figures 7, tables 2.

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Eyssa, Asmaa Abdelmonem, Fathi Elsaid Abdelsamie, and Abdelaziz Elsaid Abdelnaiem. "An Efficient Image Steganography Approach over Wireless Communication System." Wireless Personal Communications 110, no. 1 (September 21, 2019): 321–37. http://dx.doi.org/10.1007/s11277-019-06730-2.

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Abstract This paper presents a robust color image steganography approach for image communication over wireless communication systems. The objective of this approach is to hide three color images in one color cover image to increase the capacity of hiding as most previously published steganography approaches suffer from a capacity problem. Moreover, the investigation of wireless communication of steganography images is presented in this paper to study the sensitivity of extraction of hidden images to the channel degradation effects, which is not studied appropriately in the literature. The proposed approach depends on the Discrete Cosine and Discrete Wavelet transform. The cover image is first transformed to luminance and chrominance components for embedding the images to be hidden. The secret images are encrypted by chaotic Baker map, which is a good representative of the family of permutation-based algorithms, which tolerate the channel degradations better. The investigated wireless communication system is the Orthogonal Frequency Division Multiplexing system with channel equalization. The simulation results reveal the success of the proposed work for robust image communication.

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Shaheen, Imad, Abdelhalim Zekry, Fatma Newagy, and Reem Ibrahim. "PAPR reduction for FBMC/OQAM using hybrid scheme of different Precoding transform and mu-law companding." International Journal of Engineering & Technology 6, no. 4 (November 14, 2017): 154. http://dx.doi.org/10.14419/ijet.v6i4.8326.

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The filter banks multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is developing multicarrier modulation technique used in the next wireless communication system (5G). FBMC/OQAM supports high data rate and high band width efficiency. However, one of the major drawbacks of FBMC system is high peak to Average Power Ratio (PAPR) of the transmitted signal, which causes serious degradation in performance of the system. Therefore, it is required to use a proper PAPR scheme at the transmitter to reduce the PAPR. In this paper, a hybrid scheme is investigated with the combination of preceding transform technique and Mu Law Companding technique to reduce PAPR in FBMC systems. Moreover, four preceding techniques are examined to find the best Precoding technique which can be used with Mu law commanding. We assessed the discrete Hartley transform (DHT). The discrete cosine transformed (DCT), the Discrete Sine Transform (DST), and the Walsh Hadamard transforms (WHT) which are applied separately with Mu Companding. The numerical results verify that the FBMC systems with all Precoding technique combined with Mu law commanding can improve PAPR performance of the signals greatly with the best results achieved when the combination scheme consists of the DST Precoding and Mu law commanding for both PAPR and BER performance.

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Birvinskas, Darius, Vacius Jusas, Ignas Martisius, and Robertas Damasevicius. "Fast DCT algorithms for EEG data compression in embedded systems." Computer Science and Information Systems 12, no. 1 (2015): 49–62. http://dx.doi.org/10.2298/csis140101083b.

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Electroencephalography (EEG) is widely used in clinical diagnosis, monitoring and Brain - Computer Interface systems. Usually EEG signals are recorded with several electrodes and transmitted through a communication channel for further processing. In order to decrease communication bandwidth and transmission time in portable or low cost devices, data compression is required. In this paper we consider the use of fast Discrete Cosine Transform (DCT) algorithms for lossy EEG data compression. Using this approach, the signal is partitioned into a set of 8 samples and each set is DCT-transformed. The least-significant transform coefficients are removed before transmission and are filled with zeros before an inverse transform. We conclude that this method can be used in real-time embedded systems, where low computational complexity and high speed is required.

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Zear, Aditi, Amit Kumar Singh, and Pardeep Kumar. "Multiple Watermarking for Healthcare Applications." Journal of Intelligent Systems 27, no. 1 (January 26, 2018): 5–18. http://dx.doi.org/10.1515/jisys-2016-0036.

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AbstractIn this paper, an algorithm for multiple digital watermarking based on discrete wavelet transform (DWT), discrete cosine transform (DCT), and singular value decomposition (SVD) was proposed for healthcare applications such as tele-ophthalmology, tele-medicine, tele-diagnosis, and tele-consultancy services. Multiple watermarks were used in this algorithm to reduce the consequences of medical identity thefts. In the embedding process, the cover medical image was decomposed into third-level DWT. Low-frequency bands (LH2 and LL3) were transformed by DCT, and then SVD was applied to DCT coefficients. Two watermarks in the form of images were also transformed by DCT and then SVD. The singular values of the watermark information were embedded in the singular value of the cover medical image. Watermarks were extracted using an extraction algorithm. In order to enhance the robustness performance of the image watermarks, back-propagation neural network was applied to the extracted watermarks to reduce the effects of different noise applied on the watermarked image. Results were obtained by varying the gain factor and the different cover image modalities. Experimental results were provided to illustrate that the proposed method is able to withstand a variety of signal processing attacks, and has been found to give excellent performance in terms of robustness and imperceptibility. The performance of the method was also compared with other reported techniques. Further, the visual quality of the proposed method was also evaluated by a subjective method.

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Zhang, Jun, Xiaoyi Zhou, Jilin Yang, Chunjie Cao, and Jixin Ma. "Adaptive Robust Blind Watermarking Scheme Improved by Entropy-Based SVM and Optimized Quantum Genetic Algorithm." Mathematical Problems in Engineering 2019 (October 28, 2019): 1–16. http://dx.doi.org/10.1155/2019/7817809.

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With the intensive study of machine learning in digital watermarking, its ability to balance the robustness and transparency of watermarking technology has attracted researchers’ attention. Therefore, quantum genetic algorithm, which serves as an intelligent optimized scheme combined with biological genetic mechanism and quantum computing, is widely used in various fields. In this study, an adaptive robust blind watermarking algorithm by means of optimized quantum genetics (OQGA) and entropy classification-based SVM (support vector machine) is proposed. The host image was divided into two parts according to the odd and even rows of the host image. One part was transformed by DCT (discrete cosine transform), and then the embedding intensity and position were separately trained by entropy-based SVM and OQGA; the other part was by DWT (discrete wavelet transform), in which the key fusion was achieved by an ergodic matrix to embed the watermark. Simulation results indicate the proposed algorithm ensures the watermark scheme transparency as well as having better resistance to common attacks such as lossy JPEG compression, image darken, Gaussian low-pass filtering, contrast decreasing, salt-pepper noise, and geometric attacks such as rotation and cropping.

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Jittawiriyanukoon, Chanintorn, and Vilasinee Srisarkun. "Evaluation of graphic effects embedded image compression." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 6 (December 1, 2020): 6606. http://dx.doi.org/10.11591/ijece.v10i6.pp6606-6617.

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A fundamental factor of digital image compression is the conversion processes. The intention of this process is to understand the shape of an image and to modify the digital image to a grayscale configuration where the encoding of the compression technique is operational. This article focuses on an investigation of compression algorithms for images with artistic effects. A key component in image compression is how to effectively preserve the original quality of images. Image compression is to condense by lessening the redundant data of images in order that they are transformed cost-effectively. The common techniques include discrete cosine transform (DCT), fast Fourier transform (FFT), and shifted FFT (SFFT). Experimental results point out compression ratio between original RGB images and grayscale images, as well as comparison. The superior algorithm improving a shape comprehension for images with grahic effect is SFFT technique.

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El Banhawy, Magy, Walaa Saber, and Fathy Amer. "A native enhanced elastic extension tables multi-tenant database." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 6 (December 1, 2020): 6618. http://dx.doi.org/10.11591/ijece.v10i6.pp6618-6628.

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A fundamental factor of digital image compression is the conversion processes. The intention of this process is to understand the shape of an image and to modify the digital image to a grayscale configuration where the encoding of the compression technique is operational. This article focuses on an investigation of compression algorithms for images with artistic effects. A key component in image compression is how to effectively preserve the original quality of images. Image compression is to condense by lessening the redundant data of images in order that they are transformed cost-effectively. The common techniques include discrete cosine transform (DCT), fast Fourier transform (FFT), and shifted FFT (SFFT). Experimental results point out compression ratio between original RGB images and grayscale images, as well as comparison. The superior algorithm improving a shape comprehension for images with grahic effect is SFFT technique.

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DUAN, FABING, DEREK ABBOTT, and FRANÇOIS CHAPEAU-BLONDEAU. "EVALUATION OF THE SIGN DETECTOR FOR DCT DOMAIN WATERMARK DETECTION." Fluctuation and Noise Letters 10, no. 04 (December 2011): 337–58. http://dx.doi.org/10.1142/s0219477511000612.

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Reordering by the rule of decreased absolute amplitudes, the discrete cosine transformation (DCT) coefficients of an image are approximately modeled as dichotomous noise. Based on this assumption, it is interesting to note that the classical multiplicative embedding method can be transformed into an additive embedding rule, which accords with the signal processing problem of detecting a known weak signal in additive non-Gaussian noise. Then, following the generalized Neyman-Pearson lemma, a locally optimum detector, named the sign detector, is introduced to distinguish the correct watermark from the wrong ones. The statistical characteristics of this nonlinear sign detector are analytically investigated in detail. Extensive experimental results demonstrate the robustness of watermark against some common attacks, e.g., JPEG compression, cropping, filtering, additive Gaussian noise, dithering, and also verify the robust performance of the nonlinear sign detector for watermark detection.

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Khalifa, Isamadeen A., Subhi R. M. Zeebaree, Musa Ataş, and Farhad M. Khalifa. "Image Steganalysis in Frequency Domain Using Co-Occurrence Matrix and Bpnn." Science Journal of University of Zakho 7, no. 1 (March 30, 2019): 27–32. http://dx.doi.org/10.25271/sjuoz.2019.7.1.574.

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In the last two decades, steganalysis has become a fertile research area to minimize the security risks left behind by Misuse of data concealment in digital computer files. As the propagation of hidden writing increased, the need for the steganalysis emerged and grew to a large extent necessary to deter illicit secret communications. This paper introduces a steganalysis system to detect hidden information in images through using co-occurrence matrix, frequency domain transform, the first three moments, and back propagation neural network (BPNN). Four varieties of the system implemented. Firstly, the co-occurrence matrix calculated for the input image, which suspected to be a carrier of hidden secret information. Second, three levels of discrete wavelet transform (DWT) are applied resulting in 12 subbands. Then, those subbands along with the original image are transformed by discrete Fourier transform (DFT) or discrete cosine transform (DCT) to produce 13 subbands. After that, the first three moments are calculated resulting feature vector with 39 features. Finally, BPNN is used as a classifier to determine whether the image is containing hidden information or not. The system is tested with and without co-occurrence matrix, each of them once using DFT and another time using DCT. The results have shown that using co-occurrence matrix with DFT has the highest performance, which was 81.82% on the Hiding Ratio of 0.5 bit per pixel. This work demonstrates a good effect comparing to previous works.

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Deng, Tianpeng, Xuan Li, Biao Jin, Lei Chen, and Jie Lin. "Achieving Lightweight Privacy-Preserving Image Sharing and Illegal Distributor Detection in Social IoT." Security and Communication Networks 2021 (June 5, 2021): 1–13. http://dx.doi.org/10.1155/2021/5519558.

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The applications of social Internet of Things (SIoT) with large numbers of intelligent devices provide a novel way for social behaviors. Intelligent devices share images according to the groups of their specified owners. However, sharing images may cause privacy disclosure when the images are illegally distributed without owners’ permission. To tackle this issue, combining blind watermark with additive secret sharing technique, we propose a lightweight and privacy-preserving image sharing (LPIS) scheme with illegal distributor detection in SIoT. Specifically, the query user’s authentication information is embedded in two shares of the transformed encrypted image by using discrete cosine transform (DCT) and additive secret sharing technique. The robustness against attacks, such as JPEG attack and the least significant bit planes (LSBs) replacement attacks, are improved by modifying 1/8 of coefficients of the transformed image. Moreover, we adopt two edge servers to provide image storage and authentication information embedding services for reducing the operational burden of clients. As a result, the identity of the illegal distributor can be confirmed by the watermark extraction of the suspicious image. Finally, we conduct security analysis and ample experiments. The results show that LPIS is secure and robust to prevent illegal distributors from modifying images and manipulating the embedded information before unlawful sharing.

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Tsai, Tienwei, Te-Wei Chiang, and Yo-Ping Huang. "An Efficient DCT-Based Image Retrieval Approach Using Distance Threshold Pruning." Journal of Advanced Computational Intelligence and Intelligent Informatics 12, no. 3 (May 20, 2008): 268–76. http://dx.doi.org/10.20965/jaciii.2008.p0268.

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Content-based image retrieval (CBIR) techniques would allow indexing and retrieving images based on their low-level contents, which involves a large number of image pixels and thus becomes an inherently and essentially computational intensive task. This paper proposes a distance threshold pruning (DTP) method to alleviate computational burden of CBIR without sacrificing its accuracy. In our approach, the images are converted into the YUV color space, and then transformed into discrete cosine transform (DCT) coefficients. Benefited from the energy compacting property of DCT, Only the low-frequency DCT coefficients of Y, U, and V components are stored. On querying an image, at the first stage, the DTP serves as a filter to remove those candidates with widely distinct features. At the second stage, the detailed similarity comparison (DSC) is performed on those remaining candidates passing through the first stage. The experimental results show that both high efficacy and high data reduction rate can be achieved simultaneously by using the proposed approach.

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Hu, Xin Ying, and Xiu Ping Zhao. "A Robust Digital Watermarking Algorithm Based on Digital Image Security." Advanced Materials Research 174 (December 2010): 144–47. http://dx.doi.org/10.4028/www.scientific.net/amr.174.144.

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Digital watermarking has been proposed as a way to claim the ownership of the source and owner of the digital image data. In this paper, A robust algorithm based on DCT region is proposed to improve the image security. The main transforming is based on DCT (Discrete Cosine Transform). The algorithm was processed in the MATLAB software. In this paper, images of gray scale and RGB color scale were researched respectively. For color images, in order to get the best image quality, the RGB scale was transformed to YcbCr scale. Then, the Y channel (brightness channel) was separated, in which the watermark was embedded and extracted. The results show that the algorithm embedded a certain size of black and white Bitmap image into gray and color images. The watermark can’t be seen by the naked eye. The robustness detection experiment was also carried out. The watermark can still be extracted after certain amount of tailoring, defacing, Gaussian noise, and format changes. The similarity is more than 0.7. It confirmed that the algorithm is highly robust.

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Moreno-Alvarado, Rodolfo, Eduardo Rivera-Jaramillo, Mariko Nakano, and Hector Perez-Meana. "Simultaneous Audio Encryption and Compression Using Compressive Sensing Techniques." Electronics 9, no. 5 (May 22, 2020): 863. http://dx.doi.org/10.3390/electronics9050863.

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The development of coding schemes with the capacity to simultaneously encrypt and compress audio signals is a subject of active research because of the increasing necessity for transmitting sensitive audio information over insecure communication channels. Thus, several schemes have been developed; firstly, some of them compress the digital information and subsequently encrypt the resulting information. These schemas efficiently compress and encrypt the information. However, they may compromise the information as it can be accessed before encryption. To overcome this problem, a compressing sensing-based system to simultaneously compress and encrypt audio signals is proposed in which the audio signal is segmented in frames of 1024 samples and transformed into a sparse frame using the discrete cosine transform (DCT). Each frame is then multiplied by a different sensing matrix generated using the chaotic mixing scheme. This fact allows that the proposed scheme satisfies the extended Wyner secrecy (EWS) criterion. The evaluation results obtained using several genres of audio signals show that the proposed system allows to simultaneously compress and encrypt audio signals, satisfying the EWS criterion.

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Ilic, Sinisa. "Comparison of compression ratios for ECG signals by using three time-frequency transformations." Facta universitatis - series: Electronics and Energetics 20, no. 2 (2007): 223–32. http://dx.doi.org/10.2298/fuee0702223i.

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In this paper are presented compression results of ECG signal by using three time-frequency transformations: Discrete Wavelet Transform, Wavelet Packets and Modified Cosine Transform. By using transforms mentioned, samples of signals are transformed to appropriate groups of transformation coefficients. Almost all coefficients below the determined threshold are rounded to zero values and by inverse transform the similar signal to original one is created. By using run-length coder, consecutive zero value coefficients can be replaced by single value that shows how many consecutive coefficients with zero value exists. In this way small number of coefficients is stored, and compression is obtained. Depending on transform used, different number of coefficients is rounded to zero in different positions, hence the reconstructed signal is more or less similar to the original one. In general there exists measures that show how much reconstructed signal is similar to the original one, and the most used is Percentage Root mean square Difference (PRD). Comparison of compression is performed in obtaining the larger compression ratio for the smaller PRD.

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Bazine, Razika, Huayi Wu, and Kamel Boukhechba. "Spatial Filtering in DCT Domain-Based Frameworks for Hyperspectral Imagery Classification." Remote Sensing 11, no. 12 (June 13, 2019): 1405. http://dx.doi.org/10.3390/rs11121405.

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In this article, we propose two effective frameworks for hyperspectral imagery classification based on spatial filtering in Discrete Cosine Transform (DCT) domain. In the proposed approaches, spectral DCT is performed on the hyperspectral image to obtain a spectral profile representation, where the most significant information in the transform domain is concentrated in a few low-frequency components. The high-frequency components that generally represent noisy data are further processed using a spatial filter to extract the remaining useful information. For the spatial filtering step, both two-dimensional DCT (2D-DCT) and two-dimensional adaptive Wiener filter (2D-AWF) are explored. After performing the spatial filter, an inverse spectral DCT is applied on all transformed bands including the filtered bands to obtain the final preprocessed hyperspectral data, which is subsequently fed into a linear Support Vector Machine (SVM) classifier. Experimental results using three hyperspectral datasets show that the proposed framework Cascade Spectral DCT Spatial Wiener Filter (CDCT-WF_SVM) outperforms several state-of-the-art methods in terms of classification accuracy, the sensitivity regarding different sizes of the training samples, and computational time.

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Kim, Sungil, Baehyun Min, Kyungbook Lee, and Hoonyoung Jeong. "Integration of an Iterative Update of Sparse Geologic Dictionaries with ES-MDA for History Matching of Channelized Reservoirs." Geofluids 2018 (July 29, 2018): 1–21. http://dx.doi.org/10.1155/2018/1532868.

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This study couples an iterative sparse coding in a transformed space with an ensemble smoother with multiple data assimilation (ES-MDA) for providing a set of geologically plausible models that preserve the non-Gaussian distribution of lithofacies in a channelized reservoir. Discrete cosine transform (DCT) of sand-shale facies is followed by the repetition of K-singular value decomposition (K-SVD) in order to construct sparse geologic dictionaries that archive geologic features of the channelized reservoir such as pattern and continuity. Integration of ES-MDA, DCT, and K-SVD is conducted in a complementary way as the initially static dictionaries are updated with dynamic data in each assimilation of ES-MDA. This update of dictionaries allows the coupled algorithm to yield an ensemble well conditioned to static and dynamic data at affordable computational costs. Applications of the proposed algorithm to history matching of two channelized gas reservoirs show that the hybridization of DCT and iterative K-SVD enhances the matching performance of gas rate, water rate, bottomhole pressure, and channel properties with geological plausibility.

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Shi, Shanshan, Ting Luo, Jiangtao Huang, and Meng Du. "A Novel HDR Image Zero-Watermarking Based on Shift-Invariant Shearlet Transform." Security and Communication Networks 2021 (March 26, 2021): 1–12. http://dx.doi.org/10.1155/2021/6662700.

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In this paper, a novel high dynamic range (HDR) image zero-watermarking algorithm against the tone mapping attack is proposed. In order to extract stable and invariant features for robust zero-watermarking, the shift-invariant shearlet transform (SIST) is used to transform the HDR image. Firstly, the HDR image is converted to CIELAB color space, and the L component is selected to perform SIST for obtaining the low-frequency subband containing the robust structure information of the image. Secondly, the low-frequency subband is divided into nonoverlapping blocks, which are transformed by using discrete cosine transform (DCT) and singular value decomposition (SVD) to obtain the maximum singular values for constructing a binary feature image. To increase the watermarking security, a hybrid chaotic mapping (HCM) is employed to get the scrambled watermark. Finally, an exclusive-or operation is performed between the binary feature image and the scrambled watermark to compute robust zero-watermark. Experimental results show that the proposed algorithm has a good capability of resisting tone mapping and other image processing attacks.

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RENDRAGRAHA, RENDY DWI, GELAR BUDIMAN, and IRMA SAFITRI. "QIM - Based Audio Watermarking with Combination Technique of DCT-QR-CPT." ELKOMIKA: Jurnal Teknik Energi Elektrik, Teknik Telekomunikasi, & Teknik Elektronika 7, no. 1 (January 24, 2019): 112. http://dx.doi.org/10.26760/elkomika.v7i1.112.

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ABSTRAKAudio watermarking adalah teknik memasukkan informasi ke dalam file audio dan untuk melindungi hak cipta data digital dari distribusi ilegal. Makalah ini memperkenalkan audio stereo watermarking berdasarkan Quantization Index Modulation (QIM) dengan teknik gabungan Discrete Cosine Transform (DCT) - QRCartesian Polar Transform (CPT). Host audio dibagi menjadi beberapa frame, selanjutnya setiap frame ditransformasi oleh DCT, kemudian output DCT diuraikan menjadi matriks orthogonal dan matriks segitiga menggunakan metode QR. Selanjutnya, CPT mengubah dua koefisien kartesian dari matriks segitiga (R) pada posisi (1,1) dan (2,2) menjadi koefisien polar. Setelah itu, penyisipan dilakukan pada koefisien polar oleh QIM. Hasil simulasi menunjukkan bahwa imperseptibilitas audio terwatermark berkualitas baik dengan Signal to Noise Ratio (SNR)> 20, Mean Opinion Score (MOS)> 4 dan tahan terhadap serangan seperti Low Pass Filter (LPF) dan Band Pass Filter (BPF) dengan cut off 25-6k, resampling, Linear Speed Change (LSC) dan MP3 Compression dengan rate diatas 64 kbps.Kata kunci: Audio Watermarking, CPT, DCT, QIM, QR ABSTRACTAudio watermarking is a technique for inserting information into an audio file and to protect the copyright of digital data from illegal distribution. This paper introduces a stereo audio watermarking based on Quantization Index Modulation (QIM) with combined technique Discrete Cosine Transform (DCT) – QR – Cartesian Polar Transform (CPT). Each frame of a host audio is transformed by DCT, then DCT output is decomposed using QR method. Next, CPT transform two cartesian coefficients from triangular matrix (R) in position (1,1) and (2,2) to polar coefficients. After that, embedding is executed on polar coefficients by QIM. The simulation result shows that the imperceptibility is good with Signal to Noise Ratio (SNR)>20, Mean Opinion Score (MOS)>4 and it is robust against attacks such as Low Pass Filter (LPF) and Band Pass Filter (BPF) with cut off 25-6k, Resampling, Linear Speed Change and MP3 Compression with rate 64 kbps and above. Keywords: Audio Watermarking, CPT, DCT, QIM, QR

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Romaniuk, F. A., V. Yu Rumiantsev, Yu V. Rumiantsev, and V. S. Kachenya. "Orthogonal Components Forming of the Microprocessor-Based Protection Input Signals." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 63, no. 4 (August 7, 2020): 328–39. http://dx.doi.org/10.21122/1029-7448-2020-63-4-328-339.

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The use of orthogonal components (OS) is the main direction of determining information parameters in microprocessor relay protection and automation of electric power systems. Most of the measuring devices used in modern protection and automation devices can be implemented using known operating systems. Digital non-recursive frequency filters based on discrete Fourier transform are used for OS selection. The main disadvantage of these filters is their low performance that exceeds the period of industrial frequency. For the construction of high-speed measuring devices, this time of establishing the true output signal is often unacceptable. The article proposes to form the equivalent signal OS in microprocessor defenses based on the values of the cosine and sine axes of the main harmonic formed using a discrete Fourier transform, by multiplying them by a correction factor, which is a function of the values of the input signal amplitude and its main harmonic. The proposed algorithm for generating OS input signals in microprocessor defenses is characterized by high performance in transient modes and has wide functionality. A block diagram of an OS equivalent signal generator has been developed, all blocks of which can be implemented according to known schemes on a microelectronic and microprocessor element base. The OS shaper model is implemented in the MatLab-Simulink dynamic modeling environment. The model functioning was checked using two types of test actions, viz. a sinusoidal signal with a frequency of 50 Hz (idealized action) and a signal close to the real secondary current of a short-circuit current transformer. As a result of the performed calculations, a significant (up to two times) in the speed of the proposed method of OS formation in comparison with the formers based on the discrete Fourier transform, frequency properties of both formers being identical.

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Yu, Xiaoyan, Chengyou Wang, and Xiao Zhou. "A Robust Color Image Watermarking Algorithm Based on APDCBT and SSVD." Symmetry 11, no. 10 (October 2, 2019): 1227. http://dx.doi.org/10.3390/sym11101227.

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With the wide application of color images, watermarking for the copyright protection of color images has become a research hotspot. In this paper, a robust color image watermarking algorithm based on all phase discrete cosine biorthogonal transform (APDCBT) and shuffled singular value decomposition (SSVD) is proposed. The host image is transformed by the 8 × 8 APDCBT to obtain the direct current (DC) coefficient matrix, and then, the singular value decomposition (SVD) is performed on the DC matrix to embed the watermark. The SSVD and Fibonacci transform are mainly used at the watermark preprocessing stage to improve the security and robustness of the algorithm. The watermarks are color images, and a color quick response (QR) code with error correction mechanism is introduced to be a watermark to further improve the robustness. The watermark embedding and extraction processes are symmetrical. The experimental results show that the algorithm can effectively resist common image processing attacks, such as JPEG compression, Gaussian noise, salt and pepper noise, average filter, median filter, Gaussian filter, sharpening, scaling attacks, and a certain degree of rotation attacks. Compared with the color image watermarking algorithms considered in this paper, the proposed algorithm has better performance in robustness and imperceptibility.

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Journal articles on the topic 'Transformée de cosinus discrète'

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