We address the image denoising problem, where zero-mean white and homogeneous Gaussian additive noise is to be removed from a given image. The approach taken is based on sparse and redundant representations over trained dictionaries. Using the K-SVD algorithm, we obtain a dictionary that describes the image content effectively. Two training options are considered: using the corrupted image itself, or training on a corpus of high-quality image database. Since the K-SVD is limited in handling small image patches, we extend its deployment to arbitrary image sizes by defining a global image prior that forces sparsity over patches in every location in the image. We show how such Bayesian treatment leads to a simple and effective denoising algorithm. This leads to a state-of-the-art denoising performance, equivalent and sometimes surpassing recently published leading alternative denoising methods.

In recent years there has been a growing interest in the study of sparse representation of signals. Using an overcomplete dictionary that contains prototype signal-atoms, signals are described by sparse linear combinations of these atoms. Applications that use sparse representation are many and include compression, regularization in inverse problems, feature extraction, and more. Recent activity in this field has concentrated mainly on the study of pursuit algorithms that decompose signals with respect to a given dictionary. Designing dictionaries to better fit the above model can be done by either selecting one from a prespecified set of linear transforms or adapting the dictionary to a set of training signals. Both of these techniques have been considered, but this topic is largely still open. In this paper we propose a novel algorithm for adapting dictionaries in order to achieve sparse signal representations. Given a set of training signals, we seek the dictionary that leads to the best representation for each member in this set, under strict sparsity constraints. We present a new method-the K-SVD algorithm-generalizing the K-means clustering process. K-SVD is an iterative method that alternates between sparse coding of the examples based on the current dictionary and a process of updating the dictionary atoms to better fit the data. The update of the dictionary columns is combined with an update of the sparse representations, thereby accelerating convergence. The K-SVD algorithm is flexible and can work with any pursuit method (e.g., basis pursuit, FOCUSS, or matching pursuit). We analyze this algorithm and demonstrate its results both on synthetic tests and in applications on real image data.

We propose a novel image denoising strategy based on an enhanced sparse representation in transform domain. The enhancement of the sparsity is achieved by grouping similar 2-D image fragments (e.g., blocks) into 3-D data arrays which we call "groups." Collaborative filtering is a special procedure developed to deal with these 3-D groups. We realize it using the three successive steps: 3-D transformation of a group, shrinkage of the transform spectrum, and inverse 3-D transformation. The result is a 3-D estimate that consists of the jointly filtered grouped image blocks. By attenuating the noise, the collaborative filtering reveals even the finest details shared by grouped blocks and, at the same time, it preserves the essential unique features of each individual block. The filtered blocks are then returned to their original positions. Because these blocks are overlapping, for each pixel, we obtain many different estimates which need to be combined. Aggregation is a particular averaging procedure which is exploited to take advantage of this redundancy. A significant improvement is obtained by a specially developed collaborative Wiener filtering. An algorithm based on this novel denoising strategy and its efficient implementation are presented in full detail; an extension to color-image denoising is also developed. The experimental results demonstrate that this computationally scalable algorithm achieves state-of-the-art denoising performance in terms of both peak signal-to-noise ratio and subjective visual quality.

In this paper we use sparse-representation modeling for the single image scale-up problem. The goal is to recover an original image from its blurred and down-scaled noisy version. Since this problem is highly ill-posed, a prior is needed in order to solve it in a robust fashion. The literature offers various ways to address this problem, ranging from simple linear space-invariant interpolation schemes (e.g., bicubic interpolation), to spatially adaptive and non-linear filters of various sorts.In this paper, we embark from a recently-proposed algorithm by Yang et. al. [1,2], and similarly assume a local Sparse-Land model on image patches, thus stabilizing the problem. We introduce several important modifications to the above-mentioned solution, and show that these lead to improved results. These modifications include a major simplification of the overall process both in terms of the computational complexity and the algorithm architecture, using a different training approach for the dictionary-pair, and operating without a training-set by boot-strapping the scale-up task from the given low-resolution image. We demonstrate the results on true images, showing both visual and PSNR improvements.

我们提出了一种监督学习稀疏促进正规化器的方法，以降低信号和图像。促进稀疏性正则化是解决现代信号重建问题的关键要素。但是，这些正规化器的基础操作员通常是通过手动设计的，要么以无监督的方式从数据中学到。监督学习（主要是卷积神经网络）在解决图像重建问题方面的最新成功表明，这可能是设计正规化器的富有成果的方法。为此，我们建议使用带有参数，稀疏的正规器的变异公式来贬低信号，其中学会了正常器的参数，以最大程度地减少在地面真实图像和测量对的训练集中重建的平均平方误差。培训涉及解决一个具有挑战性的双层优化问题；我们使用denoising问题的封闭形式解决方案得出了训练损失梯度的表达，并提供了随附的梯度下降算法以最大程度地减少其。我们使用结构化1D信号和自然图像的实验表明，所提出的方法可以学习一个超过众所周知的正规化器（总变化，DCT-SPARSITY和无监督的字典学习）的操作员和用于DeNoisis的协作过滤。尽管我们提出的方法是特定于denoising的，但我们认为它可以适应线性测量模型的较大类反问题，使其在广泛的信号重建设置中适用。

Group sparse representation has shown promising results in image debulrring and image inpainting in GSR [3] , the main reason that lead to the success is by exploiting Sparsity and Nonlocal self-similarity (NSS) between patches on natural images, and solve a regularized optimization problem. However, directly adapting GSR[3] in image denoising yield very unstable and non-satisfactory results, to overcome these issues, this paper proposes a progressive image denoising algorithm that successfully adapt GSR [3] model and experiments shows the superior performance than some of the state-of-the-art methods.

基于深度学习的方法保持最先进的导致低级图像处理任务，但由于其黑匣子结构而难以解释。展开的优化网络通过从经典迭代优化方法导出它们的架构而不使用来自标准深度学习工具盒的技巧来构建深神经网络的可解释的替代方案。到目前为止，这种方法在使用可解释结构的同时，在使用其可解释的结构的同时证明了接近最先进的模型的性能，以实现相对的低学习参数计数。在这项工作中，我们提出了一个展开的卷积字典学习网络（CDLNET），并在低和高参数计数方面展示其竞争的去噪和联合去噪和去除脱落（JDD）性能。具体而言，我们表明，当缩放到类似的参数计数时，所提出的模型优于最先进的完全卷积的去噪和JDD模型。此外，我们利用模型的可解释结构提出了网络中阈值的噪声适应性参数化，该阈值能够实现最先进的盲目的表现，以及在训练期间看不见的噪声水平的完美概括。此外，我们表明这种性能延伸到JDD任务和无监督的学习。

在过去十年中，图像已成为许多域中的重要信息来源，因此他们的高质量是获取更好信息的必要条件。出现的重要问题是图像去噪，这意味着从不准确和/或部分测量的样品中恢复信号。这种解释与压缩感测理论高度相关，这是一种革命性的技术，并且意味着如果信号稀疏，则可以从几个测量值获得原始信号，这些值远低于其他使用的理论所建议的值像Shannon的抽样理论。压缩传感（CS）理论的强因素以实现稀疏性解决方案以及从损坏的图像中移除的噪声是基础词典的选择。在本文中，比较了基于压缩感测和稀疏近似理论的高斯粘性白噪声的离散余弦变换（DCT）和力矩变换（TCHEBICHEF，KRAWTCHOUK）。实验结果表明，由矩变换构建的基本词典竞争性地表现为传统的DCT。后一种变换显示了30.82dB的PSNR，与Tchebichef变换相同的0.91 SSIM值。此外，从稀疏性的角度来看，Krawtchouk时刻提供大约20-30％的稀疏结果比DCT更多。

实际图像的稀疏表示是成像应用的非常有效的方法，例如去噪。近年来，随着计算能力的增长，利用一个或多个图像提取的补丁内冗余的数据驱动策略，以增加稀疏性变得更加突出。本文提出了一种新颖的图像去噪算法，利用了由量子多体理论的图像依赖性的基础。基于补丁分析，通过类似于量子力学的术语来形式化局部图像邻域中的相似度测量，可以有效地保留真实图像的局部结构的量子力学中的相互作用。这种自适应基础的多功能性质将其应用范围扩展到图像无关或图像相关的噪声场景，而无需任何调整。我们对当代方法进行严格的比较，以证明所提出的算法的去噪能力，无论图像特征，噪声统计和强度如何。我们说明了超参数的特性及其对去噪性能的各自影响，以及自动化规则，可以在实验设置中选择其值的自动化规则，其实际设置不可用。最后，我们展示了我们对诸如医用超声图像检测应用等实际图像的方法处理实际图像的能力。

高光谱成像为各种应用提供了新的视角，包括使用空降或卫星遥感，精密养殖，食品安全，行星勘探或天体物理学的环境监测。遗憾的是，信息的频谱分集以各种劣化来源的牺牲品，并且目前获取的缺乏准确的地面“清洁”高光谱信号使得恢复任务具有挑战性。特别是，与传统的RGB成像问题相比，培训深度神经网络用于恢复难以深入展现的传统RGB成像问题。在本文中，我们提倡基于稀疏编码原理的混合方法，其保留与手工图像前导者编码域知识的经典技术的可解释性，同时允许在没有大量数据的情况下训练模型参数。我们在各种去噪基准上展示了我们的方法是计算上高效并且显着优于现有技术。

We introduce a parametric view of non-local two-step denoisers, for which BM3D is a major representative, where quadratic risk minimization is leveraged for unsupervised optimization. Within this paradigm, we propose to extend the underlying mathematical parametric formulation by iteration. This generalization can be expected to further improve the denoising performance, somehow curbed by the impracticality of repeating the second stage for all two-step denoisers. The resulting formulation involves estimating an even larger amount of parameters in a unsupervised manner which is all the more challenging. Focusing on the parameterized form of NL-Ridge, the simplest but also most efficient non-local two-step denoiser, we propose a progressive scheme to approximate the parameters minimizing the risk. In the end, the denoised images are made up of iterative linear combinations of patches. Experiments on artificially noisy images but also on real-world noisy images demonstrate that our method compares favorably with the very best unsupervised denoisers such as WNNM, outperforming the recent deep-learning-based approaches, while being much faster.

约束的张量和矩阵分子化模型允许从多道数据中提取可解释模式。因此，对于受约束的低秩近似度的可识别性特性和有效算法是如此重要的研究主题。这项工作涉及低秩近似的因子矩阵的列，以众所周知的和可能的过度顺序稀疏，该模型包括基于字典的低秩近似（DLRA）。虽然早期的贡献集中在候选列字典内的发现因子列，即一稀疏的近似值，这项工作是第一个以大于1的稀疏性解决DLRA。我建议专注于稀疏编码的子问题，在解决DLRA时出现的混合稀疏编码（MSC）以交替的优化策略在解决DLRA时出现。提供了基于稀疏编码启发式的几种算法（贪婪方法，凸起放松）以解决MSC。在模拟数据上评估这些启发式的性能。然后，我展示了如何基于套索来调整一个有效的MSC求解器，以计算高光谱图像处理和化学测量学的背景下的基于词典的基于矩阵分解和规范的多adic分解。这些实验表明，DLRA扩展了低秩近似的建模能力，有助于降低估计方差并提高估计因子的可识别性和可解释性。

可分离的或克朗克蛋白产品，字典为2D信号提供自然分解，例如图像。在本文中，我们描述了一种高度平行化的算法，该算法学习此词典，该词典达到漏洞表示与文献中的前一种艺术字典学习算法的先前状态，但以较低的计算成本。我们突出了所提出的方法稀疏地代表图像和高光谱数据的性能，以及用于图像去噪。

信号或数据的稀疏表示（SR）具有良好的创立理论，具有严格的数学误差界和证明。信号的SR由矩阵的叠加为称为字典的叠加，隐含地减少了维度。培训词典使它们表示具有最小损失的每种信号称为字典学习（DL）。字典学习方法，如最佳方向（MOD）和K-SVD的方法，已成功地用于图像处理中的重建应用，如图像“去噪”，“伪装”等。其他判别k-svd和标签一致的K-SVD等字典学习算法是基于K-SVD的监督学习方法。在我们的经验中，当前方法的一个缺点是，在Telugu OCR数据集等数据集中，分类性能并不令人印象深刻，具有大量的课程和高维度。在这个方向上有所改善，许多研究人员使用统计方法来设计分类词典。本章介绍了统计技术的审查及其在学习歧视性词典中的应用。这里描述的方法的目的是使用稀疏表示来改善分类。在本章中，描述了混合方法，其中生成输入数据的稀疏系数。我们使用一个简单的三层多层Perceptron，背传播培训作为具有输入的稀疏代码的分类器。结果与其他计算密集型方法相当可比。关键词：统计建模，字典学习，歧视性词典，稀疏表示，高斯先前，Cauchy先前，熵，隐马尔可夫模型，混合词典学习

在这项工作中，我们引入了一种新的随机算法被称为剪辑，其从任何线性逆问题的后部分布绘制样品，其中假设观察被添加的白色高斯噪声污染。我们的解决方案包含Langevin Dynamics和Newton的方法的想法，并利用预训练的最小均方误差（MMSE）高斯丹麦置位。所提出的方法依赖于包括劣化运算符的奇异值分解（SVD）的后续函数的复杂衍生，以获得所需采样的易迭代算法。由于其瞬极性，算法可以为同样嘈杂的观察产生多个高感性质量样本。我们展示了拟议的图像去掩饰，超分辨率和压缩感测的范例的能力。我们表明所产生的样品是尖锐的，详细且与给定的测量结果一致，它们的多样性暴露了解决的逆问题中的固有不确定性。

Deep neural networks provide unprecedented performance gains in many real world problems in signal and image processing. Despite these gains, future development and practical deployment of deep networks is hindered by their blackbox nature, i.e., lack of interpretability, and by the need for very large training sets. An emerging technique called algorithm unrolling or unfolding offers promise in eliminating these issues by providing a concrete and systematic connection between iterative algorithms that are used widely in signal processing and deep neural networks. Unrolling methods were first proposed to develop fast neural network approximations for sparse coding. More recently, this direction has attracted enormous attention and is rapidly growing both in theoretic investigations and practical applications. The growing popularity of unrolled deep networks is due in part to their potential in developing efficient, high-performance and yet interpretable network architectures from reasonable size training sets. In this article, we review algorithm unrolling for signal and image processing. We extensively cover popular techniques for algorithm unrolling in various domains of signal and image processing including imaging, vision and recognition, and speech processing. By reviewing previous works, we reveal the connections between iterative algorithms and neural networks and present recent theoretical results. Finally, we provide a discussion on current limitations of unrolling and suggest possible future research directions.

我们在凸优化和深度学习的界面上引入了一类新的迭代图像重建算法，以启发凸出和深度学习。该方法包括通过训练深神网络（DNN）作为Denoiser学习先前的图像模型，并将其替换为优化算法的手工近端正则操作员。拟议的airi（``````````````'''''）框架，用于成像复杂的强度结构，并从可见性数据中扩散和微弱的发射，继承了优化的鲁棒性和解释性，以及网络的学习能力和速度。我们的方法取决于三个步骤。首先，我们从光强度图像设计了一个低动态范围训练数据库。其次，我们以从数据的信噪比推断出的噪声水平来训练DNN Denoiser。我们使用训练损失提高了术语，可确保算法收敛，并通过指示进行即时数据库动态范围增强。第三，我们将学习的DeNoiser插入前向后的优化算法中，从而产生了一个简单的迭代结构，该结构与梯度下降的数据输入步骤交替出现Denoising步骤。我们已经验证了SARA家族的清洁，优化算法的AIRI，并经过DNN训练，可以直接从可见性数据中重建图像。仿真结果表明，AIRI与SARA及其基于前卫的版本USARA具有竞争力，同时提供了显着的加速。干净保持更快，但质量较低。端到端DNN提供了进一步的加速，但质量远低于AIRI。

本文介绍了使用基于补丁的先前分布的图像恢复的新期望传播（EP）框架。虽然Monte Carlo技术典型地用于从难以处理的后分布中进行采样，但它们可以在诸如图像恢复之类的高维推论问题中遭受可扩展性问题。为了解决这个问题，这里使用EP来使用多元高斯密度的产品近似后分布。此外，对这些密度的协方差矩阵施加结构约束允许更大的可扩展性和分布式计算。虽然该方法自然适于处理添加剂高斯观察噪声，但它也可以扩展到非高斯噪声。用于高斯和泊松噪声的去噪，染色和去卷积问题进行的实验说明了这种柔性近似贝叶斯方法的潜在益处，以实现与采样技术相比降低的计算成本。

基于深度学习（DL）的高光谱图像（HSIS）去噪方法直接学习观察到的嘈杂图像和底层清洁图像之间的非线性映射。他们通常不考虑HSIS的物理特征，因此使他们缺乏了解他们的去噪机制的关键。为了解决这个问题，我们为HSI去噪提出了一种新颖的模型指导可解释网络。具体而言，完全考虑HSI的空间冗余，光谱低秩和光谱空间特性，我们首先建立基于子空间的多维稀疏模型。该模型首先将观察到的HSIS投入到低维正交子空间，然后表示具有多维字典的投影图像。之后，该模型展开到名为SMDS-Net的端到端网络中，其基本模块与模型的去噪程序无缝连接。这使得SMDS-Net传达清晰的物理意义，即学习HSIS的低级别和稀疏性。最后，通过端到端培训获得包括词典和阈值处理的所有关键变量。广泛的实验和综合分析证实了我们对最先进的HSI去噪方法的方法的去噪能力和可解释性。

通过最近基于深度学习的方法显示出令人鼓舞的结果，可以消除图像中的噪音，在有监督的学习设置中报道了最佳的降级性能，该设置需要大量的配对嘈杂图像和训练的基础真相。强大的数据需求可以通过无监督的学习技术来减轻，但是，对于高质量的解决方案，图像或噪声方差的准确建模仍然至关重要。对于未知的噪声分布而言，学习问题不足。本文研究了单个联合学习框架中图像降解和噪声方差估计的任务。为了解决问题的不良性，我们提出了深度差异先验（DVP），该差异指出，适当学到的DeNoiser在噪声变化方面的变化满足了一些平滑度的特性，这是良好DeNoiser的关键标准。建立在DVP的基础上，这是一个无监督的深度学习框架，同时学习了Denoiser并估算了噪声差异。我们的方法不需要任何干净的训练图像或噪声估计的外部步骤，而是仅使用一组嘈杂的图像近似于最小平方误差Denoisiser。在一个框架中考虑了两个基本任务，我们允许它们相互优化。实验结果表明，具有与监督的学习和准确的噪声方差估计值相当的质量。