{"title":"WARPd: A Linearly Convergent First-Order Primal-Dual Algorithm for Inverse Problems with Approximate Sharpness Conditions","authors":"Matthew J. Colbrook","doi":"10.1137/21m1455000","DOIUrl":"https://doi.org/10.1137/21m1455000","url":null,"abstract":"Sharpness conditions directly control the recovery performance of restart schemes for first-order optimization methods without the need for restrictive assumptions such as strong convexity. However, they are challenging to apply in the presence of noise or approximate model classes (e.g., approximate sparsity). We provide a first-order method: weighted, accelerated, and restarted primal-dual (WARPd), based on primal-dual iterations and a novel restart-reweight scheme. Under a generic approximate sharpness condition, WARPd achieves stable linear convergence to the desired vector. Many problems of interest fit into this framework. For example, we analyze sparse recovery in compressed sensing, low-rank matrix recovery, matrix completion, TV regularization, minimization of ∥Bx∥l1 under constraints (l-analysis problems for general B), and mixed regularization problems. We show how several quantities controlling recovery performance also provide explicit approximate sharpness constants. Numerical experiments show that WARPd compares favorably with specialized state-of-the-art methods and is ideally suited for solving large-scale problems. We also present a noise-blind variant based on a square-root LASSO decoder. Finally, we show how to unroll WARPd as neural networks. This approximation theory result provides lower bounds for stable and accurate neural networks for inverse problems and sheds light on architecture choices. Code and a gallery of examples are available online as a MATLAB package.","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"315 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122111947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Spatial Color Compensation Model Using Saturation-Value Total Variation","authors":"Wei Wang, Yu-Miao Yang, M. K. Ng","doi":"10.1137/21m1453773","DOIUrl":"https://doi.org/10.1137/21m1453773","url":null,"abstract":"","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131735464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"$L_1$-Norm Regularization for Short-and-Sparse Blind Deconvolution: Point Source Separability and Region Selection","authors":"Weixi Wang, Ji Li, Hui Ji","doi":"10.1137/21m144904x","DOIUrl":"https://doi.org/10.1137/21m144904x","url":null,"abstract":". Blind deconvolution is about estimating both the convolution kernel and the latent signal from their 5 convolution. Many blind deconvolution problems have a short-and-sparse (SaS) structure, i.e . the 6 signal (or its gradient) is sparse and the kernel size is much smaller than the signal size. While ℓ 1 -norm 7 relating regularizations have been widely used for solving SaS blind deconvolution problems, the so- 8 called region/edge selection technique brings great empirical improvement to such ℓ 1 -norm relating 9 regularizations in image deblurring. The essence of region/edge selection is during an alternative 10 iterative scheme of SaS blind deconvolution, one estimates the kernel on an estimate of the latent 11 image with well-separated image edges instead of the one with the least fitting error. In this paper, 12 we first examines the validity and soundness of ℓ 1 -norm relating regularization in the setting of 1D 13 SaS blind deconvolution. The analysis reveals the importance of the separation of non-zero signal 14 entries toward the soundness of such a regularization. The studies laid out the foundation of region 15 selection technique, i.e ., during the iteration, an estimate of the latent image with well-separated 16 edges is a better candidate for estimating the kernel than the one with least fitting error. Based 17 on the studies conducted in this paper, an alternating iterative scheme with region selection model 18 is developed for SaS blind deconvolution, which is then applied on blind motion deblurring. The 19 experiments showed its effectiveness over many existing ℓ 1 -norm relating approaches. 20","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125198477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Budd, Y. Gennip, J. Latz, S. Parisotto, C. Schönlieb
{"title":"Joint reconstruction-segmentation on graphs","authors":"J. Budd, Y. Gennip, J. Latz, S. Parisotto, C. Schönlieb","doi":"10.1137/22M151546X","DOIUrl":"https://doi.org/10.1137/22M151546X","url":null,"abstract":"Practical image segmentation tasks concern images which must be reconstructed from noisy, distorted, and/or incomplete observations. A recent approach for solving such tasks is to perform this reconstruction jointly with the segmentation, using each to guide the other. However, this work has so far employed relatively simple segmentation methods, such as the Chan--Vese algorithm. In this paper, we present a method for joint reconstruction-segmentation using graph-based segmentation methods, which have been seeing increasing recent interest. Complications arise due to the large size of the matrices involved, and we show how these complications can be managed. We then analyse the convergence properties of our scheme. Finally, we apply this scheme to distorted versions of ``two cows'' images familiar from previous graph-based segmentation literature, first to a highly noised version and second to a blurred version, achieving highly accurate segmentations in both cases. We compare these results to those obtained by sequential reconstruction-segmentation approaches, finding that our method competes with, or even outperforms, those approaches in terms of reconstruction and segmentation accuracy.","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114850156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Niall Donlon, Romina Gaburro, S. Moskow, Isaac D. Woods
{"title":"Stability and Reconstruction of a Special Type of Anisotropic Conductivity in Magneto-Acoustic Tomography with Magnetic Induction","authors":"Niall Donlon, Romina Gaburro, S. Moskow, Isaac D. Woods","doi":"10.1137/22m1512260","DOIUrl":"https://doi.org/10.1137/22m1512260","url":null,"abstract":"We consider the issues of stability and reconstruction of the electrical anisotropic conductivity of biological tissues in a domain $Omegasubsetmathbb{R}^3$ by means of the hybrid inverse problem of magneto-acoustic tomography with magnetic induction (MAT-MI). The class of anisotropic conductivities considered here is of type $sigma(cdot)=A(cdot,gamma(cdot))$ in $Omega$, where $[lambda^{-1}, lambda]ni tmapsto A(cdot, t)$ is a one-parameter family of matrix-valued functions which are textit{a-priori} known to be $C^{1,beta}$, allowing us to stably reconstruct $gamma$ in $Omega$ in terms of an internal functional $F(sigma)$. Our results also extend previous results in MAT-MI where $sigma(cdot) = gamma(cdot) D(cdot)$, with $D$ an textit{a-priori} known matrix-valued function on $Omega$ to a more general anisotropic structure which depends non-linearly on the scalar function $gamma$ to be reconstructed.","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115511834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Separable Quaternion Matrix Factorization for Polarization Images","authors":"Junjun Pan, Michael K. Ng","doi":"10.48550/arXiv.2207.14039","DOIUrl":"https://doi.org/10.48550/arXiv.2207.14039","url":null,"abstract":"Polarization is a unique characteristic of transverse wave and is represented by Stokes parameters. Analysis of polarization states can reveal valuable information about the sources. In this paper, we propose a separable low-rank quaternion linear mixing model to polarized signals: we assume each column of the source factor matrix equals a column of polarized data matrix and refer to the corresponding problem as separable quaternion matrix factorization (SQMF). We discuss some properties of the matrix that can be decomposed by SQMF. To determine the source factor matrix in quaternion space, we propose a heuristic algorithm called quaternion successive projection algorithm (QSPA) inspired by the successive projection algorithm. To guarantee the effectiveness of QSPA, a new normalization operator is proposed for the quaternion matrix. We use a block coordinate descent algorithm to compute nonnegative factor activation matrix in real number space. We test our method on the applications of polarization image representation and spectro-polarimetric imaging unmixing to verify its effectiveness.","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114241697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stable Image Reconstruction Using Transformed Total Variation Minimization","authors":"Limei Huo, Wengu Chen, Huanmin Ge, M. K. Ng","doi":"10.1137/21m1438566","DOIUrl":"https://doi.org/10.1137/21m1438566","url":null,"abstract":"","PeriodicalId":185319,"journal":{"name":"SIAM J. Imaging Sci.","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134113312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}