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Variational methods have become an important kind of methods in signal and image restoration - a typical inverse problem. One important minimization model consists of the squared $\ell_2$ data fidelity (corresponding to Gaussian noise) and…

Numerical Analysis · Mathematics 2018-06-15 Chunlin Wu , Zhifang Liu , Shuang Wen

The curvature regularities are well-known for providing strong priors in the continuity of edges, which have been applied to a wide range of applications in image processing and computer vision. However, these models are usually non-convex,…

Numerical Analysis · Mathematics 2019-12-03 Qiuxiang Zhong , Ke Yin , Yuping Duan

We show how total variation regularization of images in arbitrary dimensions can be approximately performed by applying appropriate shrinkage to some Haar wavelets coefficients. The approach works directly on the wavelet coefficients and is…

Numerical Analysis · Mathematics 2024-11-04 Tomas Sauer , A. Michael Stock

In this paper we present a novel iterative procedure for multichannel image and data reconstruction using Bregman distances. With the motivation that multiple channels sharing a common subgradient with respect to a suitable regularization…

Numerical Analysis · Mathematics 2014-12-18 Michael Moeller , Eva-Maria Brinkmann , Martin Burger , Tamara Seybold

The aim of this paper is to test and analyze a novel technique for image reconstruction in positron emission tomography, which is based on (total variation) regularization on both the image space and the projection space. We formulate our…

Numerical Analysis · Mathematics 2014-07-24 Martin Burger , Jahn Müller , Evangelos Papoutsellis , Carola-Bibiane Schönlieb

Total Variation (TV) based regularization has been widely applied in restoration problems due to its simple derivative filters based formulation and robust performance. While first order TV suffers from staircase effect, second order TV…

Signal Processing · Electrical Eng. & Systems 2019-04-08 Sanjay Viswanath , Muthuvel Arigovindan

Compressed sensing (CS) methods in magnetic resonance imaging (MRI) offer rapid acquisition and improved image quality but require iterative reconstruction schemes with regularization to enforce sparsity. Regardless of the difficulty in…

Computer Vision and Pattern Recognition · Computer Science 2018-09-19 Raji Susan Mathew , Joseph Suresh Paul

Total Generalized Variation (TGV) regularization in image reconstruction relies on an infimal convolution type combination of generalized first- and second-order derivatives. This helps to avoid the staircasing effect of Total Variation…

Optimization and Control · Mathematics 2022-05-09 Michael Hintermüller , Kostas Papafitsoros , Carlos N. Rautenberg , Hongpeng Sun

Total variation (TV) regularization is a popular reconstruction method for ill-posed imaging problems, and particularly useful for applications with piecewise constant targets. However, using TV for medical cone-beam computed X-ray…

Medical Physics · Physics 2024-12-11 Alexander Meaney , Mikael A. K. Brix , Miika T. Nieminen , Samuli Siltanen

Based on transformed $\ell_1$ regularization, transformed total variation (TTV) has robust image recovery that is competitive with other nonconvex total variation (TV) regularizers, such as TV$^p$, $0<p<1$. Inspired by its performance, we…

Computer Vision and Pattern Recognition · Computer Science 2024-06-05 Elisha Dayag , Kevin Bui , Fredrick Park , Jack Xin

Discrete gradient methods are well-known methods of Geometric Numerical Integration, which preserve the dissipation of gradient systems. The preservation of the dissipation of a system is an important feature in numerous image processing…

Numerical Analysis · Mathematics 2016-03-25 V Grimm , R I McLachlan , D McLaren , G R W Quispel , C-B Schönlieb

In inverse problems, prior information and a priori-based regularization techniques play important roles. In this paper, we focus on image restoration problems, especially on restoring images whose texture mainly follow one direction. In…

Numerical Analysis · Mathematics 2017-08-23 Rasmus Dalgas Kongskov , Yiqiu Dong , Kim Knudsen

We introduce a novel family of invariant, convex, and non-quadratic functionals that we employ to derive regularized solutions of ill-posed linear inverse imaging problems. The proposed regularizers involve the Schatten norms of the Hessian…

Optimization and Control · Mathematics 2014-02-20 Stamatios Lefkimmiatis , John Paul Ward , Michael Unser

The total variation (TV)-seminorm is considered for piecewise polynomial, globally discontinuous (DG) and continuous (CG) finite element functions on simplicial meshes. A novel, discrete variant (DTV) based on a nodal quadrature formula is…

Numerical Analysis · Mathematics 2018-08-17 Marc Herrmann , Roland Herzog , Stephan Schmidt , José Vidal-Núñez , Gerd Wachsmuth

The least-square regression problems or inverse problems have been widely studied in many fields such as compressive sensing, signal processing, and image processing. To solve this kind of ill-posed problems, a regularization term (i.e.,…

Numerical Analysis · Mathematics 2014-05-12 Gang Liu , Ting-Zhu Huang , Xiao-Guang Lv , Jun Liu

Existing deep-learning based tomographic image reconstruction methods do not provide accurate estimates of reconstruction uncertainty, hindering their real-world deployment. This paper develops a method, termed as the linearised deep image…

Image and Video Processing · Electrical Eng. & Systems 2022-11-07 Javier Antorán , Riccardo Barbano , Johannes Leuschner , José Miguel Hernández-Lobato , Bangti Jin

In a number of tomographic applications, data cannot be fully acquired, resulting in a severely underdetermined image reconstruction. In such cases, conventional methods lead to reconstructions with significant artifacts. To overcome these…

Numerical Analysis · Mathematics 2023-06-21 Simon Göppel , Jürgen Frikel , Markus Haltmeier

Optimization within a layer of a deep-net has emerged as a new direction for deep-net layer design. However, there are two main challenges when applying these layers to computer vision tasks: (a) which optimization problem within a layer is…

Computer Vision and Pattern Recognition · Computer Science 2022-04-08 Raymond A. Yeh , Yuan-Ting Hu , Zhongzheng Ren , Alexander G. Schwing

Total variation (TV) regularization has proven effective for a range of computer vision tasks through its preferential weighting of sharp image edges. Existing TV-based methods, however, often suffer from the over-smoothing issue and…

Computer Vision and Pattern Recognition · Computer Science 2018-12-26 Dong Gong , Mingkui Tan , Qinfeng Shi , Anton van den Hengel , Yanning Zhang

In this paper, we propose Total Variation Regularized Tensor-on-scalar Regression(TVTR), a novel method for estimating the association between a tensor outcome (a one dimensional or multidimensional array) and scalar predictors. While the…

Methodology · Statistics 2018-12-11 Ying Liu , Bowei Yan , Kathleen Merikangas , Haochang Shou