scispace - formally typeset
Search or ask a question
Topic

Hadamard transform

About: Hadamard transform is a research topic. Over the lifetime, 7262 publications have been published within this topic receiving 94328 citations.


Papers
More filters
Patent
Paul W. Dent1
25 Jul 1991
TL;DR: A processor for generating a Walsh transform by substantially simultaneously calculating M combinations of M input values, wherein M=2N and the input values are two's-complement binary values, has N stages electrically connected in sequence, wherein each stage has a crisscross network of M conductors electrically connecting in a predetermined pattern to a set of M/2 butterflies, the butterflies having devices for calculating sums and differences of respective values presented by their respective criss-cross networks.
Abstract: A processor for generating a Walsh transform by substantially simultaneously calculating M combinations of M input values, wherein M=2N and the input values are two's-complement binary values, has N stages electrically connected in sequence, wherein each stage has a criss-cross network of M conductors electrically connected in a predetermined pattern to a set of M/2 butterflies, the butterflies having devices for calculating sums and differences of respective values presented by their respective criss-cross networks and presenting the sums and differences to respective conductors of the next stage's criss-cross network. The input values are presented to the criss-cross network of the first stage serially and least-significant-bit first, and substantially synchronously therewith, the Walsh transform of the input values is serially produced by the butterflies of the N-th stage.

37 citations

Journal ArticleDOI
TL;DR: The experimental results show that the proposed watermarking method, while providing transparency, is robust against many image processing attacks such as compression, image cropping and Gaussian filtering.
Abstract: Nowadays, due to widespread usage of the Internet, digital contents are distributed quickly and inexpensively throughout the world. Watermarking techniques can help protect authenticity of digital contents by identifying their owners. In a watermarking procedure, owner information may be embedded in the spatial domain or transform domain of host images. Since watermarking algorithms must be tamper resistant and transparent, we present a watermarking method based on a transform domain. In this method, we employ Hadamard transform as it requires simpler operations compared to other transforms such as discrete cosine transform (DCT) and discrete wavelet transform (DWT) while it still attains robustness. We analyze each bit of the Hadamard’s coefficients in terms of robustness and transparency for hiding the watermark information and find a bit-plane that maintains both robustness and transparency. After that, watermark information is hidden redundantly in the selected bit-plane. The proposed extraction algorithm is classified as a blind algorithm since it extracts all versions of the concealed watermark with no information from the host image. The output of the extraction algorithm is a logo obtained by an intelligent voting among all versions of the hidden logo. The experimental results show that the proposed method, while providing transparency, is robust against many image processing attacks such as compression, image cropping and Gaussian filtering.

37 citations

Journal ArticleDOI
TL;DR: High-speed algorithms to compute the discrete Hadamard and Walsh transforms of speech waveforms have been developed and a digital processor, which allows real-time analysis of speech to be conducted on the system, is described.
Abstract: High-speed algorithms to compute the discrete Hadamard and Walsh transforms of speech waveforms have been developed. Intelligible speech has been reconstructed from dominant Hadamard or Walsh coefficients on a medium sized computer in a non-real-time mode. Degradation of some phonemes was noted at low bit rates of reconstruction, but the reconstruction could be improved by varying the position of the sampling window. A digital processor, which allows real-time analysis of speech to be conducted on the system, is described.

37 citations

Journal ArticleDOI
TL;DR: This correspondence presents new construction methods for quaternary low-correlation zone (LCZ) sequence sets from a binary sequence with good autocorrelation and shows that the sets obtained are optimal or nearly optimal with respect to the Tang-Fan-Matsufuji bound.
Abstract: In this correspondence, we present new construction methods for quaternary low-correlation zone (LCZ) sequence sets from a binary sequence with good autocorrelation. We show that the sets obtained by our methods are optimal or nearly optimal with respect to the Tang-Fan-Matsufuji bound and that our construction methods are more flexible than any other previous constructions in the sense of period, family size, and zone size. We also give a construction method for a quaternary LCZ sequence set from a binary LCZ sequence set. Finally, we give a new construction method for quaternary Hadamard matrices by the inverse of the Gray map.

37 citations

Proceedings ArticleDOI
01 Apr 1987
TL;DR: A Gaussian probabilistic model was developed to screen and select from the large set of features and the significant harmonics of the signature were sorted according to the chi-square value, which is equivalent to the signal-to-noise ratio.
Abstract: Features such as shape, motion and pressure, minutiae details and timing, and transformation methods such as Hadamard and Walsh have been used in signature recognition with various degrees of success. One of the better studies was done by Sato and Kogure using nonlinear warping function. However, it is time consuming in terms of computer time and programming time. In this research, the signatures were normalized for size, orientation, etc. After normalization, the X and Y coordinates of each sampled point of a signature over time (to capture the dynamics of signature writing) were represented as a complex number and the set of complex numbers transformed into the frequency domain via the fast Fourier transform. A Gaussian probabilistic model was developed to screen and select from the large set of features (e.g. amplitude of each harmonics). The significant harmonics of the signature were sorted according to the chi-square value, which is equivalent to the signal-to-noise ratio. Fifteen harmonics with the largest signal-to-noise ratios from the true signatures were used in a discriminant analysis. A total of eight true signatures from a single person and eight each from nineteen forgers were used. It results in an error rate of 2.5%, with the normally more conservative jacknife procedure yielding the same small error rate.

37 citations


Network Information
Related Topics (5)
Bounded function
77.2K papers, 1.3M citations
85% related
Matrix (mathematics)
105.5K papers, 1.9M citations
85% related
Differential equation
88K papers, 2M citations
85% related
Iterative method
48.8K papers, 1.2M citations
85% related
Upper and lower bounds
56.9K papers, 1.1M citations
84% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023339
2022850
2021391
2020444
2019427
2018372