The Experts below are selected from a list of 33 Experts worldwide ranked by ideXlab platform
Stephen Hardy - One of the best experts on this subject based on the ideXlab platform.
-
Affine-Invariant Image Watermarking Using the Hyperbolic Chirp
2009 Digital Image Computing: Techniques and Applications, 2009Co-Authors: Peter Fletcher, Kieran Larkin, Stephen HardyAbstract:Image watermarking is the robust, imperceptible embedding of a small quantity of data into a digital image, and the subsequent recovery of this data, perhaps after the watermarked image has been distorted. We present a new watermarking technique which is robust to many image distortions, in particular arbitrary affine transformations of the image. The method achieves its robustness through the use of one-dimensional Chirp functions. An affine-invariant detection method exists for such functions using a Radon transform, yet they are not detected trivially by a malicious attacker. The method also provides a way to determine any affine transformation applied to the watermarked image by using an affine-invariant property of groups of intersecting lines.
Peter Fletcher - One of the best experts on this subject based on the ideXlab platform.
-
Affine-Invariant Image Watermarking Using the Hyperbolic Chirp
2009 Digital Image Computing: Techniques and Applications, 2009Co-Authors: Peter Fletcher, Kieran Larkin, Stephen HardyAbstract:Image watermarking is the robust, imperceptible embedding of a small quantity of data into a digital image, and the subsequent recovery of this data, perhaps after the watermarked image has been distorted. We present a new watermarking technique which is robust to many image distortions, in particular arbitrary affine transformations of the image. The method achieves its robustness through the use of one-dimensional Chirp functions. An affine-invariant detection method exists for such functions using a Radon transform, yet they are not detected trivially by a malicious attacker. The method also provides a way to determine any affine transformation applied to the watermarked image by using an affine-invariant property of groups of intersecting lines.
Kieran Larkin - One of the best experts on this subject based on the ideXlab platform.
-
Affine-Invariant Image Watermarking Using the Hyperbolic Chirp
2009 Digital Image Computing: Techniques and Applications, 2009Co-Authors: Peter Fletcher, Kieran Larkin, Stephen HardyAbstract:Image watermarking is the robust, imperceptible embedding of a small quantity of data into a digital image, and the subsequent recovery of this data, perhaps after the watermarked image has been distorted. We present a new watermarking technique which is robust to many image distortions, in particular arbitrary affine transformations of the image. The method achieves its robustness through the use of one-dimensional Chirp functions. An affine-invariant detection method exists for such functions using a Radon transform, yet they are not detected trivially by a malicious attacker. The method also provides a way to determine any affine transformation applied to the watermarked image by using an affine-invariant property of groups of intersecting lines.
Jesús Ponce De León - One of the best experts on this subject based on the ideXlab platform.
-
Estimation of the instantaneous amplitude and the instantaneous frequency of audio signals using complex wavelets
Signal Processing, 2010Co-Authors: José Ramón Beltrán, Jesús Ponce De LeónAbstract:This work presents a method of analyzing and synthesizing audio signals that uses complex wavelets. In the method, the input signal is filtered by a complex bandpass filter bank through a discrete version of the complex continuous wavelet transform. A general theoretical signal with time-dependent amplitude and phase has been analyzed. The analysis of the information provided by the modulus and the phase of the complex continuous wavelet transform was used to develop an additive analysis/synthesis algorithm for audio signals called complex wavelet additive synthesis. To illustrate the method, this new algorithm has been used to analyze the following four synthetic, non-stationary signals that have different frequency variation laws: a linear Chirp, a quadratic Chirp, a Hyperbolic Chirp and an FM signal with a sinusoidal excursion. Finally, the validity of the algorithm has been tested by comparing the results of an analysis of two real sounds with the proposed algorithm and with one existing technique, namely spectral modelling synthesis (SMS).
Stephen James Hardy - One of the best experts on this subject based on the ideXlab platform.
-
Tenacious Image Tagging with Hyperbolic Chirps
2012Co-Authors: Kieran G. Larkin, Peter Alleine Fletcher, Stephen James HardyAbstract:We describe a method for attaching persistent metadata to an image. The method can be interpreted as a template-based blind watermarking scheme, robust to common editing operations, namely: cropping, rotation, scaling, stretching, shearing, compression, printing, scanning, noise, and color removal. Robustness is achieved through the reciprocity of the embedding and detection invariants. The embedded patterns are one-dimensional Hyperbolic Chirp patterns distributed over two-dimensions. The embedded patterns are scale invariant and can be directly embedded in an image by simple pixel addition. Detection achieves rotation and general affine invariance by signal projection using implicit Radon transformation. Embedded signals contract to one-dimension in the two-dimensional Fourier polar domain. The real signals are detected by correlation with complex Hyperbolic Chirp templates. Using a unique template of 4 Chirp patterns we detect the affine signature with exquisite sensitivity and moderate security. The practical implementation achieves efficiencies through fast Fourier transform (FFT) correspondences such as the projectionslice theorem, the FFT correlation relation, and fast resampling via the Chirp-z transform. The overall method performs well in terms of the classic robustness-capacity-visibility performance triangle. Watermarked images survive almost all Stirmark attacks. The method is ideal for attaching metadata robustly to both digital and analogue images. EDICS: COM-WSE Image & Video Processing for Watermarking and Security