327 research outputs found
A General Destriping Framework for Remote Sensing Images Using Flatness Constraint
This paper proposes a general destriping framework using flatness
constraints, where we can handle various regularization functions in a unified
manner. Removing stripe noise, i.e., destriping, from remote sensing images is
an essential task in terms of visual quality and subsequent processing. Most of
the existing methods are designed by combining a particular image
regularization with a stripe noise characterization that cooperates with the
regularization, which precludes us to examine different regularizations to
adapt to various target images. To resolve this, we formulate the destriping
problem as a convex optimization problem involving a general form of image
regularization and the flatness constraints, a newly introduced stripe noise
characterization. This strong characterization enables us to consistently
capture the nature of stripe noise, regardless of the choice of image
regularization. For solving the optimization problem, we also develop an
efficient algorithm based on a diagonally preconditioned primal-dual splitting
algorithm (DP-PDS), which can automatically adjust the stepsizes. The
effectiveness of our framework is demonstrated through destriping experiments,
where we comprehensively compare combinations of image regularizations and
stripe noise characterizations using hyperspectral images (HSI) and infrared
(IR) videos.Comment: submitted to IEEE Transactions on Geoscience and Remote Sensin
Robust Hyperspectral Image Fusion with Simultaneous Guide Image Denoising via Constrained Convex Optimization
The paper proposes a new high spatial resolution hyperspectral (HR-HS) image
estimation method based on convex optimization. The method assumes a low
spatial resolution HS (LR-HS) image and a guide image as observations, where
both observations are contaminated by noise. Our method simultaneously
estimates an HR-HS image and a noiseless guide image, so the method can utilize
spatial information in a guide image even if it is contaminated by heavy noise.
The proposed estimation problem adopts hybrid spatio-spectral total variation
as regularization and evaluates the edge similarity between HR-HS and guide
images to effectively use apriori knowledge on an HR-HS image and spatial
detail information in a guide image. To efficiently solve the problem, we apply
a primal-dual splitting method. Experiments demonstrate the performance of our
method and the advantage over several existing methods.Comment: Accepted to IEEE Transactions on Geoscience and Remote Sensin
Sparse Index Tracking: Simultaneous Asset Selection and Capital Allocation via -Constrained Portfolio
Sparse index tracking is one of the prominent passive portfolio management
strategies that construct a sparse portfolio to track a financial index. A
sparse portfolio is desirable over a full portfolio in terms of transaction
cost reduction and avoiding illiquid assets. To enforce the sparsity of the
portfolio, conventional studies have proposed formulations based on
-norm regularizations as a continuous surrogate of the -norm
regularization. Although such formulations can be used to construct sparse
portfolios, they are not easy to use in actual investments because parameter
tuning to specify the exact upper bound on the number of assets in the
portfolio is delicate and time-consuming. In this paper, we propose a new
problem formulation of sparse index tracking using an -norm constraint
that enables easy control of the upper bound on the number of assets in the
portfolio. In addition, our formulation allows the choice between portfolio
sparsity and turnover sparsity constraints, which also reduces transaction
costs by limiting the number of assets that are updated at each rebalancing.
Furthermore, we develop an efficient algorithm for solving this problem based
on a primal-dual splitting method. Finally, we illustrate the effectiveness of
the proposed method through experiments on the S\&P500 and NASDAQ100 index
datasets.Comment: Submitted to IEEE Open Journal of Signal Processin
Variable-Wise Diagonal Preconditioning for Primal-Dual Splitting: Design and Applications
This paper proposes a method of designing appropriate diagonal
preconditioners for a preconditioned primal-dual splitting method (P-PDS).
P-PDS can efficiently solve various types of convex optimization problems
arising in signal processing and image processing. Since the appropriate
diagonal preconditioners that accelerate the convergence of P-PDS vary greatly
depending on the structure of the target optimization problem, a design method
of diagonal preconditioners for PPDS has been proposed to determine them
automatically from the problem structure. However, the existing method has two
limitations: it requires direct access to all elements of the matrices
representing the linear operators involved in the target optimization problem,
and it is element-wise preconditioning, which makes certain types of proximity
operators impossible to compute analytically. To overcome these limitations, we
establish an Operator-norm-based design method of Variable-wise Diagonal
Preconditioning (OVDP). First, the diagonal preconditioners constructed by OVDP
are defined using only the operator norm or its upper bound of the linear
operator thus eliminating the need for their explicit matrix representations.
Furthermore, since our method is variable-wise preconditioning, it keeps all
proximity operators efficiently computable. We also prove that our
preconditioners satisfy the convergence conditions of PPDS. Finally, we
demonstrate the effectiveness and utility of our method through applications to
hyperspectral image mixed noise removal, hyperspectral unmixing, and graph
signal recovery.Comment: Submitted to IEEE Transactions on Signal Processin
Graph Spatio-Spectral Total Variation Model for Hyperspectral Image Denoising
The spatio-spectral total variation (SSTV) model has been widely used as an
effective regularization of hyperspectral images (HSI) for various applications
such as mixed noise removal. However, since SSTV computes local spatial
differences uniformly, it is difficult to remove noise while preserving complex
spatial structures with fine edges and textures, especially in situations of
high noise intensity. To solve this problem, we propose a new TV-type
regularization called Graph-SSTV (GSSTV), which generates a graph explicitly
reflecting the spatial structure of the target HSI from noisy HSIs and
incorporates a weighted spatial difference operator designed based on this
graph. Furthermore, we formulate the mixed noise removal problem as a convex
optimization problem involving GSSTV and develop an efficient algorithm based
on the primal-dual splitting method to solve this problem. Finally, we
demonstrate the effectiveness of GSSTV compared with existing HSI
regularization models through experiments on mixed noise removal. The source
code will be available at https://www.mdi.c.titech.ac.jp/publications/gsstv.Comment: Accepted to IEEE Geoscience and Remote Sensing Letters. The code is
available at https://www.mdi.c.titech.ac.jp/publications/gsst
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