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Applying standard algorithms to sparse data problems in photoacoustic tomography (PAT) yields low-quality images containing severe under-sampling artifacts. To some extent, these artifacts can be reduced by iterative image reconstruction…

Numerical Analysis · Mathematics 2024-12-20 Stephan Antholzer , Johannes Schwab , Robert Nuster , Markus Haltmeier

We give a new approach to the dictionary learning (also known as "sparse coding") problem of recovering an unknown $n\times m$ matrix $A$ (for $m \geq n$) from examples of the form \[ y = Ax + e, \] where $x$ is a random vector in $\mathbb…

Data Structures and Algorithms · Computer Science 2014-11-11 Boaz Barak , Jonathan A. Kelner , David Steurer

Super-symmetric tensors - a higher-order extension of scatter matrices - are becoming increasingly popular in machine learning and computer vision for modelling data statistics, co-occurrences, or even as visual descriptors. However, the…

Computer Vision and Pattern Recognition · Computer Science 2015-09-11 Piotr Koniusz , Anoop Cherian

Many imaging science tasks can be modeled as a discrete linear inverse problem. Solving linear inverse problems is often challenging, with ill-conditioned operators and potentially non-unique solutions. Embedding prior knowledge, such as…

Numerical Analysis · Mathematics 2023-12-07 Elizabeth Newman , Jack Michael Solomon , Matthias Chung

Dictionary Learning (DL) is one of the leading sparsity promoting techniques in the context of image classification, where the "dictionary" matrix D of images and the sparse matrix X are determined so as to represent a redundant image…

Numerical Analysis · Mathematics 2022-03-10 Domitilla Brandoni , Margherita Porcelli , Valeria Simoncini

State-of-the-art learned reconstruction methods often rely on black-box modules that, despite their strong performance, raise questions about their interpretability and robustness. Here, we build on a recently proposed image reconstruction…

Image and Video Processing · Electrical Eng. & Systems 2026-05-19 Joshua Schulz , David Schote , Christoph Kolbitsch , Kostas Papafitsoros , Andreas Kofler

The aim of this paper is to introduce a novel dictionary learning algorithm for sparse representation of signals defined over combinatorial topological spaces, specifically, regular cell complexes. Leveraging Hodge theory, we embed topology…

Signal Processing · Electrical Eng. & Systems 2025-03-17 Enrico Grimaldi , Claudio Battiloro , Paolo Di Lorenzo

Dictionary learning is the problem of estimating the collection of atomic elements that provide a sparse representation of measured/collected signals or data. This paper finds fundamental limits on the sample complexity of estimating…

Information Theory · Computer Science 2018-03-06 Zahra Shakeri , Waheed U. Bajwa , Anand D. Sarwate

We frame the task of predicting a semantic labeling as a sparse reconstruction procedure that applies a target-specific learned transfer function to a generic deep sparse code representation of an image. This strategy partitions training…

Computer Vision and Pattern Recognition · Computer Science 2014-10-17 Michael Maire , Stella X. Yu , Pietro Perona

In this paper, we propose a new sampling strategy for hyperspectral signals that is based on dictionary learning and singular value decomposition (SVD). Specifically, we first learn a sparsifying dictionary from training spectral data using…

Computer Vision and Pattern Recognition · Computer Science 2015-12-04 Mingrui Yang , Frank de Hoog , Yuqi Fan , Wen Hu

We address the multi-focus image fusion problem, where multiple images captured with different focal settings are to be fused into an all-in-focus image of higher quality. Algorithms for this problem necessarily admit the source image…

Computer Vision and Pattern Recognition · Computer Science 2019-05-06 Farshad G. Veshki , Sergiy A. Vorobyov

Matrix congruence extends naturally to the setting of tensors. We apply methods from tensor decomposition, algebraic geometry and numerical optimization to this group action. Given a tensor in the orbit of another tensor, we compute a…

Numerical Analysis · Mathematics 2018-11-26 Max Pfeffer , Anna Seigal , Bernd Sturmfels

To ensure interpretability of extracted sources in tensor decomposition, we introduce in this paper a dictionary-based tensor canonical polyadic decomposition which enforces one factor to belong exactly to a known dictionary. A new…

Machine Learning · Statistics 2018-03-13 Jérémy E. Cohen , Nicolas Gillis

This paper is concerned with the approximation of high-dimensional functions in a statistical learning setting, by empirical risk minimization over model classes of functions in tree-based tensor format. These are particular classes of…

Machine Learning · Statistics 2019-01-15 Erwan Grelier , Anthony Nouy , Mathilde Chevreuil

Dictionary learning aims at seeking a dictionary under which the training data can be sparsely represented. Methods in the literature typically formulate the dictionary learning problem as an optimization w.r.t. two variables, i.e.,…

Signal Processing · Electrical Eng. & Systems 2021-10-27 Cheng Cheng , Wei Dai

Binary tomography is concerned with the recovery of binary images from a few of their projections (i.e., sums of the pixel values along various directions). To reconstruct an image from noisy projection data, one can pose it as a…

Image and Video Processing · Electrical Eng. & Systems 2020-12-17 Ajinkya Kadu , Tristan van Leeuwen

Ptychography is a powerful computational imaging technique that transforms a collection of low-resolution images into a high-resolution sample reconstruction. Unfortunately, algorithms that are currently used to solve this reconstruction…

Dictionary learning aims to find a dictionary that can sparsely represent the training data. Methods in the literature typically formulate the dictionary learning problem as an optimisation with respect to two variables, i.e., dictionary…

Signal Processing · Electrical Eng. & Systems 2019-11-21 Cheng Cheng , Wei Dai

Dictionary learning algorithms have been successfully used for both reconstructive and discriminative tasks, where an input signal is represented with a sparse linear combination of dictionary atoms. While these methods are mostly developed…

Machine Learning · Statistics 2016-01-20 Soheil Bahrampour , Nasser M. Nasrabadi , Asok Ray , W. Kenneth Jenkins

We propose defensive tensorization, an adversarial defence technique that leverages a latent high-order factorization of the network. The layers of a network are first expressed as factorized tensor layers. Tensor dropout is then applied in…