The Experts below are selected from a list of 36627 Experts worldwide ranked by ideXlab platform
Muhammad Rafiq Abuturab - One of the best experts on this subject based on the ideXlab platform.
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securing color image using discrete cosine transform in gyrator transform domain structured phase encoding
Optics and Lasers in Engineering, 2012Co-Authors: Muhammad Rafiq AbuturabAbstract:Abstract A new method for securing color image using discrete cosine transform in gyrator transform domain structured-phase encoding is proposed. In this proposal, the structured phase mask is a zone plate phase function. The input color image to be encrypted is decomposed into three channels: red, green, and blue. Each of these channels is encrypted independently by changing its spatial distribution of pixel value by discrete cosine transform, and encoded with structured phase mask. The gyrator transform is performed on resultant spectrum. Structured phase mask, discrete cosine transform, and gyrator transform are employed twice in this proposed method. The construction parameters of structured phase mask and angle parameters of gyrator transform in each channel are principal encryption keys. The schematic electro-optical implementation has been presented. The proposed architecture does not require axial movements. The effectiveness of the proposed algorithm is demonstrated against the chosen and known plaintext attacks. Numerical simulations are made to verify the security, validity, and capability of the proposed method.
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color information security system using discrete cosine transform in gyrator transform domain radial hilbert phase encoding
Optics and Lasers in Engineering, 2012Co-Authors: Muhammad Rafiq AbuturabAbstract:Abstract A novel color-information encryption technique based on discrete cosine transform and radial Hilbert phase mask in gyrator transform domain is proposed. In this work, the radial Hilbert phase function is employed as selected phase mask. Before the encryption, the original color image is converted into independent channels, i.e. red, green, and blue. Each channel is encrypted using first random phase mask and discrete cosine transform at input plane, and then the first gyrator transform is executed. The obtained image is again encrypted using second random phase mask and discrete cosine transform at frequency plane, and then transmitted through radial Hibert phase mask. The gyrator transform is performed on the transmitted image. The integral orders of radial Hibert phase mask and transformation angles of gyrator transform in each channel provide supplementary keys to enhance the security. The proposed system evades the misalignment problems. Numerical simulations are demonstrated to test the security, validity, and efficiency of the proposed algorithm.
Kaoru Sezaki - One of the best experts on this subject based on the ideXlab platform.
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reversible discrete cosine transform
International Conference on Acoustics Speech and Signal Processing, 1998Co-Authors: Kunitoshi Komatsu, Kaoru SezakiAbstract:In this paper a reversible discrete cosine transform (RDCT) is presented. The N-point reversible transform is firstly presented, then the 8-point RDCT is obtained by substituting the 2 and 4-point reversible transforms for the 2 and 4-point transforms which compose the 8-point discrete cosine transform (DCT), respectively. The integer input signal can be losslessly recovered, although the transform coefficients are integer numbers. If the floor functions are ignored in RDCT, the transform is exactly the same as DCT with determinant=1. RDCT is also normalized so that we can avoid the problem that dynamic range is nonuniform. A simulation on continuous-tone still images shows that the lossless and lossy compression efficiencies of RDCT are comparable to those obtained with reversible wavelet transform.
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ICASSP - Reversible discrete cosine transform
Proceedings of the 1998 IEEE International Conference on Acoustics Speech and Signal Processing ICASSP '98 (Cat. No.98CH36181), 1Co-Authors: Kunitoshi Komatsu, Kaoru SezakiAbstract:In this paper a reversible discrete cosine transform (RDCT) is presented. The N-point reversible transform is firstly presented, then the 8-point RDCT is obtained by substituting the 2 and 4-point reversible transforms for the 2 and 4-point transforms which compose the 8-point discrete cosine transform (DCT), respectively. The integer input signal can be losslessly recovered, although the transform coefficients are integer numbers. If the floor functions are ignored in RDCT, the transform is exactly the same as DCT with determinant=1. RDCT is also normalized so that we can avoid the problem that dynamic range is nonuniform. A simulation on continuous-tone still images shows that the lossless and lossy compression efficiencies of RDCT are comparable to those obtained with reversible wavelet transform.
Enrico Magli - One of the best experts on this subject based on the ideXlab platform.
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steerable discrete cosine transform
IEEE Transactions on Image Processing, 2017Co-Authors: Giulia Fracastoro, Sophie M Fosson, Enrico MagliAbstract:In image compression, classical block-based separable transforms tend to be inefficient when image blocks contain arbitrarily shaped discontinuities. For this reason, transforms incorporating directional information are an appealing alternative. In this paper, we propose a new approach to this problem, namely, a discrete cosine transform (DCT) that can be steered in any chosen direction. Such transform, called steerable DCT (SDCT), allows to rotate in a flexible way pairs of basis vectors, and enables precise matching of directionality in each image block, achieving improved coding efficiency. The optimal rotation angles for SDCT can be represented as solution of a suitable rate-distortion (RD) problem. We propose iterative methods to search such solution, and we develop a fully fledged image encoder to practically compare our techniques with other competing transforms. Analytical and numerical results prove that SDCT outperforms both DCT and state-of-the-art directional transforms.
Kunitoshi Komatsu - One of the best experts on this subject based on the ideXlab platform.
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reversible discrete cosine transform
International Conference on Acoustics Speech and Signal Processing, 1998Co-Authors: Kunitoshi Komatsu, Kaoru SezakiAbstract:In this paper a reversible discrete cosine transform (RDCT) is presented. The N-point reversible transform is firstly presented, then the 8-point RDCT is obtained by substituting the 2 and 4-point reversible transforms for the 2 and 4-point transforms which compose the 8-point discrete cosine transform (DCT), respectively. The integer input signal can be losslessly recovered, although the transform coefficients are integer numbers. If the floor functions are ignored in RDCT, the transform is exactly the same as DCT with determinant=1. RDCT is also normalized so that we can avoid the problem that dynamic range is nonuniform. A simulation on continuous-tone still images shows that the lossless and lossy compression efficiencies of RDCT are comparable to those obtained with reversible wavelet transform.
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ICASSP - Reversible discrete cosine transform
Proceedings of the 1998 IEEE International Conference on Acoustics Speech and Signal Processing ICASSP '98 (Cat. No.98CH36181), 1Co-Authors: Kunitoshi Komatsu, Kaoru SezakiAbstract:In this paper a reversible discrete cosine transform (RDCT) is presented. The N-point reversible transform is firstly presented, then the 8-point RDCT is obtained by substituting the 2 and 4-point reversible transforms for the 2 and 4-point transforms which compose the 8-point discrete cosine transform (DCT), respectively. The integer input signal can be losslessly recovered, although the transform coefficients are integer numbers. If the floor functions are ignored in RDCT, the transform is exactly the same as DCT with determinant=1. RDCT is also normalized so that we can avoid the problem that dynamic range is nonuniform. A simulation on continuous-tone still images shows that the lossless and lossy compression efficiencies of RDCT are comparable to those obtained with reversible wavelet transform.
L Westover - One of the best experts on this subject based on the ideXlab platform.
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a forward mapping realization of the inverse discrete cosine transform
Data Compression Conference, 1992Co-Authors: Leonard Mcmillan, L WestoverAbstract:The paper presents a new realization of the inverse discrete cosine transform (IDCT). It exploits both the decorrelation properties of the discrete cosine transform (DCT) and the quantization process that is frequently applied to the DCT's resultant coefficients. This formulation has several advantages over previous approaches, including the elimination of multiplies from the central loop of the algorithm and its adaptability to incremental evaluation. The technique provides a significant reduction in computational requirements of the IDCT, enabling a software-based implementation to perform at rates which were previously achievable only through dedicated hardware. >
