Improving super-resolution mapping through combining multiple super-resolution land-cover maps

Super-resolution mapping (SRM) is an ill-posed problem, and different SRM algorithms may generate non-identical fine-spatial resolution land-cover maps (sub-pixel maps) from the same input coarse-spatial resolution image. The output sub-pixels maps may each have differing strengths and weaknesses. A multiple SRM (M-SRM) method that combines the sub-pixel maps obtained from a set of SRM analyses, obtained from a single or multiple set of algorithms, is proposed in this study. Plurality voting, which selects the class with the most votes, is used to label each sub-pixel. In this study, three popular SRM algorithms, namely, the pixel-swapping algorithm (PSA), the Hopfield neural network (HNN) algorithm, and the Markov random field (MRF)-based algorithm, were used. The proposed M-SRM algorithm was validated using two data sets: a simulated multispectral image and an Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral image. Results show that the highest overall accuracies were obtained by M-SRM in all experiments. For example, in the AVIRIS image experiment, the highest overall accuracies of PSA, HNN, and MRF were 88.89, 93.81, and 82.70%, respectively, and these increased to 95.06, 95.37, and 85.56%, respectively for M-SRM obtained from the multiple PSA, HNN, and MRF analyses.     

A study of a Gaussian mixture model for urban land-cover mapping based on VHR remote sensing imagery

This article proposes a Gaussian-mixture-model (GMM)-based method with optimal Gaussian components to address the high intra-class spectral variability in urban land-cover mapping using remote sensing images with very high resolution (VHR). GMMs can simulate and approximate any data distribution provided the optimal Gaussian components can be found. Through improving the model parameters in view of the characteristic of VHR remote sensing images, the parameter space of GMM is optimized significantly, and the model can find the optimal Gaussian components that are suitable for remote sensing images with different resolutions. Experimental results of Wuhan urban area using two images with different resolutions have demonstrated the efficiency and effectiveness of the model. The optimized GMM-based method performs at least comparably or superior to the state-of-the-art classifiers such as support vector machines (SVMs), characterizes man-made land-cover types better than conventional methods, fuses spectral and textural features of VHR image properly, and meanwhile has lower computational complexity.     

A local structure adaptive super-resolution reconstruction method based on BTV regularization

Super-resolution (SR) image reconstruction has been one of the hottest research fields in recent years. The main idea of SR is to utilize complementary information from a set of low resolution (LR) images of the same scene to reconstruct a high-resolution image with more details. Under the framework of the regularization based SR, this paper presents a local structure adaptive BTV regularization based super-resolution reconstruction method to overcome the shortcoming of the Bilateral Total Variation (BTV) super resolution reconstruction model. The proposed method adaptively chooses prior model and regularization parameter according to the local structures. Experimental results show that the proposed method can get better reconstruction results and significantly reduces the manual workload of the regularization parameter selection.     

Locally affine patch mapping and global refinement for image super-resolution

This paper deals with the super-resolution (SR) problem based on a single low-resolution (LR) image. Inspired by the local tangent space alignment algorithm in [16] for nonlinear dimensionality reduction of manifolds, we propose a novel patch-learning method using locally affine patch mapping (LAPM) to solve the SR problem. This approach maps the patch manifold of low-resolution image to the patch manifold of the corresponding high-resolution (HR) image. This patch mapping is learned by a training set of pairs of LR/HR images, utilizing the affine equivalence between the local low-dimensional coordinates of the two manifolds. The latent HR image of the input (an LR image) is estimated by the HR patches which are generated by the proposed patch mapping on the LR patches of the input. We also give a simple analysis of the reconstruction errors of the algorithm LAPM. Furthermore we propose a global refinement technique to improve the estimated HR image. Numerical results are given to show the efficiency of our proposed methods by comparing these methods with other existing algorithms.     

Annual land-cover mapping based on multi-temporal cloud-contaminated landsat images

Landsat images, which have fine spatial resolution, are an important data source for land-cover mapping. Multi-temporal Landsat classification has become popular because of the abundance of free-access Landsat images that are available. However, cloud cover is inevitable due to the relatively low temporal frequency of the data. In this paper, a novel approach for multi-temporal Landsat land-cover classification is proposed. The land cover for each Landsat acquisition date was first classified using a Support Vector Machine (SVM) and then the classification results were combined using different strategies, with missing observations allowed. Three strategies, including the majority vote (MultiSVM-MV), Expectation Maximisation (MultiSVM-EM) and joint SVM probability (JSVM), were used to merge the multi-temporal classification maps. The three algorithms were then applied to a region of the path/row 143/31 scene using 2010 Landsat-5 Thematic Mapper (TM) images. The results demonstrated that, for these three algorithms, the average overall accuracy (OA) improved with the increase in temporal depth; also, for a given temporal depth, the performance of JSVM was clearly better than that of MultiSVM-MV and MultiSVM-EM, and the performance of MultiSVM-EM was slightly better than that of MultiSVM-MV. The OA values for the three classification results, which use all epochs, were 70.28%, 72.40% and 74.80% for MultiSVM-MV, MultiSVM-EM and JSVM, respectively. In comparison, two other annual composite image-based classification methods, annual maximum Normalised Difference Vegetation Index (NDVI) composite image-based classification and annual best-available-pixel (BAP) composite image-based classification, gave OA values of 68.08% and 69.92%, respectively, meaning that our method produced a better performance. Therefore, the novel multi-temporal Landsat classification method presented in this paper can deal with the cloud-contamination problem and produce accurate annual land-cover mapping using multi-temporal cloud-contaminated images, which is of importance for regional and global land-cover mapping.     

An adaptive regression based single-image super-resolution

Multimedia Tools and Applications - Image super-resolution (SR) is an important topic of low-level computer vision and is widely used in different fields. In this paper, a novel single-image SR...     

Multi-kernel based adaptive interpolation for image super-resolution

This paper proposes a cost-effective and edge-directed image super-resolution scheme. Image super-resolution (image magnification) is an enthusiastic research area and is desired in a variety of applications. The basic idea of the proposed scheme is based on the concept of multi-kernel approach. Various stencils have been defined on the basis of geometrical regularities. This set of stencils is associated with the set of kernels. The value of a re-sampling pixel is obtained by calculating the weighted average of the pixels in the selected kernel. The time complexity of the proposed scheme is as low as that of classical linear interpolation techniques, but the visual quality is more appealing because of the edge-orientation property. The experimental results and analysis show that proposed scheme provides a good combination of visual quality and time complexity.     

基于自适应半耦合字典学习的超分辨率图像重建

在超分辨图像重建领域,如何平衡字典学习中表示系数的稀疏性和协同性对重建效果具有重要意义。针对该问题,在半耦合字典学习的超分辨重建基础上,利用核范数构建一个新的正则项,将稀疏性和协同性作为一个整体进行考虑,并用交替方向乘子法(ADMM)求解优化模型,得到了基于自适应半耦合字典学习的超分辨率图像重建算法。实验结果表明,该方法比现有的一些基于字典学习的重建方法具有更好的重建效果,其能根据字典的变化自适应地平衡稀疏性与关联性,并通过两者之间的协调产生一个最合适的系数,因此在噪声环境下具有一定的抗干扰能力。     

基于自适应锚定邻域回归的图像超分辨率算法

在基于字典的图像超分辨率（SR）算法中，锚定邻域回归超分辨率（ANR）算法由于其优越的重建速度和质量引起了人们的广泛关注。然而，ANR算法的锚定邻域投影并不稳定，以致于不足以涵盖各种样式的映射关系。因此提出一种基于自适应锚定邻域回归的图像SR算法，根据样本分布自适应地计算邻域中心从而以更精确的邻域来预计算投影矩阵。首先，以图像块为中心，运用K均值聚类算法将训练样本聚类成不同的簇；然后，用每个簇的聚类中心替换字典原子来计算相应的邻域；最后，运用这些邻域来预计算从低分辨率（LR）空间到高分辨率（HR）空间的映射矩阵。实验结果表明，所提算法在Set14上平均重建效果以31.56 dB的峰值信噪比（PSNR）及0.8712的结构相似性（SSIM）优于其他基于字典的先进算法，甚至胜过超分辨率卷积神经网络（SRCNN）算法。同时，在主观表现上看，所提算法恢复出了尖锐的图像边缘且产生的伪影较少。     

Single image super-resolution via multiple linear mapping anchored neighborhood regression

Multimedia Tools and Applications - The goal of learning-based image super-resolution (SR) is to generate a plausible and visually high-resolution (HR) image from a single low-resolution (LR) input...     

基于自适应注意力融合特征提取网络的图像超分辨率

为了应对当前大型图像超分辨率模型参数过多难以部署,以及现有的轻量级图像超分辨率模型性能表现不佳的问题,提出了一种基于自适应注意力融合特征提取网络的图像超分辨率模型。该模型主要由一个大核注意力模块和多个高效注意力融合特征提取模块组成。首先,利用大核注意力模块进行浅层特征提取,然后将提取到的浅层特征信息输入级联的高效注意力融合特征提取模块进行深层特征提取、增强、细化和再分配的聚合操作。高效注意力融合特征提取模块由三个部分组成,分别是渐进式残差特征提取模块、通道对比度感知注意力模块和通道—空间联合注意力模块。该网络可以在利用少量参数的情况下实现更好的图像超分辨率性能,是一种表现优异的轻量级图像超分辨率模型。通过在流行的基准数据集上评估提出的方法,并与现有的一些方法进行对比,结果表明该方法的表现更优异。     

基于改进量化约束集的压缩视频超分辨率重建算法

摘要：超分辨率技术是使用低分辨率图像序列来重建高分辨率图像的技术。在压缩视频的超分辨率重建中,量化约束集(QCS)作为编码模型的先验信息被广泛采用。根据窄量化约束集(NQCS)理论,利用量化误差的统计特性,提出了一种改进量化约束集(AQCS)。根据DCT变换后块边界特性,提出了平滑约束集。实验结果表明,提出的基于改进量化约束集的压缩视频超分辨率重建算法较传统的量化约束集,在峰值信噪比(PSNR)和主观图像质量上有不同程度的提高。     

结合超分辨率重建的神经网络亚像元定位方法

遥感影像中普遍存在着混合像元,如何分析和解译混合像元一直是人们研究的热点。亚像元定位方法是将混合像元分解成为亚像元,并赋予不同的端元组分,以提高影像整体分类精度的一种技术。本文在神经网络亚像元定位模型的基础上,结合超分辨率重建理论,提出一种新型的BPMAP模型,在每一个类别的组成分图像与亚像元定位图像之间建立起高、低分辨率的观测模型,采用最大后验估计（MAP）算法对BP神经网络的定位结果进行约束,最终确定混合像元内部各组分合适的空间位置。通过对模拟的简单图像和长江三峡地区的ETM影像进行实验,结果表明,与神经网络模型相比,本文方法能够更加有效地解决亚像元定位的问题,进一步消除定位过程中产生的误差,提高精度。     

基于POCS框架的时空联合自适应视频超分辨率重建算法*

针对传统POCS( projection onto convex sets)算法的局限性,提出了一种基于POCS框架的时空联合自适应视频超分辨率重建算法.通过引入时空联合自适应机制,算法有效地减缓了错误运动估计信息对重建图像质量的影响,克服了传统POCS算法对目标运动剧烈的视频序列重建时存在的噪声放大效应.实验结果表明...     

Single image super-resolution based on space structure learning

In this paper, the learning-based single image super-resolution (SR) is regarded as a problem of space structure learning. We propose a new SR method that identifies a space from the low-resolution (LR) image space that best preserves the structure of the high-resolution (HR) image space. The inference between the two structure-consistent spaces proves to be accurate and predicts HR image patches with higher quality. An effective iterative algorithm is also proposed to find the near-optimal solution to the model, which can be easily implemented in parallel computing. Extensive experiments are performed to show the effectiveness of the proposed algorithm.     

基于双变量收缩函数的局域自适应图像去噪

由于图像小波系数存在很大的层间相关性,引入双变量概率分布模型,基于贝叶斯估计理论,得到了相应的非线性阈值函数（双变量收缩函数）;基于层内局域方差估计,利用该收缩函数得到一种局域自适应的图像去噪算法。在实验中,将该算法分别应用到实值离散小波变换域和双树复数小波变换域,并和隐马尔科夫模型的去噪方法做了比较分析。实验表明,复数小波变换的局域自适应收缩图像去噪算法去噪效果最好。     

基于自适应约束正则HL-MRF先验模型的MAP超分辨率重建

针对Huber-MRF先验模型对图像高频噪声抑制能力较差,而Gauss-MRF先验模型对图像高频过度惩罚的问题,提出了一种改进的自适应约束正则HL-MRF先验模型。该模型将Huber边缘惩罚低频函数与Lorentzian边缘惩罚高频函数相结合,对低频进行线性约束的同时对高频实现平滑惩罚;并采用自适应约束方法确定正则化参数,从而得到最优的参数解。与基于Gauss-MRF先验模型和Huber-MRF先验模型的超分辨率算法相比,HL-MRF先验模型获得的超分辨率重建图像在峰值信噪比(PSNR)和细节方面都有一定程度的提高,在抑制高频噪声、避免图像细节被过度平滑方面具有一定的优势。     

Soft-then-hard super-resolution mapping based on a spatial attraction model with multiscale sub-pixel shifted images

Super-resolution mapping (SRM) is a technique for exploring spatial distribution information of the land-cover classes at finer spatial resolution. The soft-then-hard super-resolution mapping (STHSRM) algorithm is a type of SRM algorithm that first estimates the soft class values for sub-pixels at the target fine spatial resolution and then predicts the hard class labels for sub-pixels. The sub-pixel shifted images from the same area can be incorporated to improve the accuracy of STHSRM algorithm. In this article, multiscale sub-pixel shifted images (MSSI) based on the fine-scale model and the coarse-scale model are utilized to increase the accuracy of STHSRM. First, class fraction images are derived from multiple sub-pixel shifted coarse spatial resolution images by soft classification. Then using the sub-pixel/sub-pixel spatial attraction model as fine-scale and the sub-pixel/pixel spatial attraction model as coarse scale, all MSSI can be derived from fraction images. The MSSI for each class are then integrated to obtain the desired fine spatial resolution images. Finally, the integrated fine spatial resolution images are used to allocate classes for sub-pixel. Experiments on two synthetic remote sensing images and a real hyperspectral remote sensing imagery show that the proposed method produces higher mapping accuracy result.     

RGB-D结构相似性度量下的多边自适应深度图像超分辨率重建

目的 深度相机能够对场景的深度信息进行实时动态捕捉,但捕获的深度图像分辨率低且容易形成空洞。利用高分辨率彩色图像作为引导,是深度图超分辨率重建的重要方式。现有方法对彩色边缘与深度不连续区域的不一致性问题难以有效解决,在深度图超分辨率重建中引入了纹理复制伪影。针对这一问题,本文提出了一种鲁棒的彩色图像引导的深度图超分辨率重建算法。方法 首先,利用彩色图像边缘与深度图像边缘的结构相关性,提出RGB-D结构相似性度量,检测彩色图像与深度图像共有的边缘不连续区域,并利用RGB-D结构相似性度量自适应选取估计像素点邻域的最优图像块。接着,通过提出的定向非局部均值权重,在图像块区域内建立多边引导下的深度估计,解决彩色边缘和深度不连续区域的结构不一致性。最后,利用RGB-D结构相似性度量与图像平滑性之间的对应关系,对多边引导权重的参数进行自适应调节,实现鲁棒的深度图超分辨率重建。结果 在Middlebury合成数据集、ToF和Kinect数据集以及本文自建数据集上的实验结果表明,相比其他先进方法,本文方法能够有效抑制纹理复制伪影。在Middlebury、ToF和Kinect数据集上,本文方法相较于次优算法,平均绝对偏差平均降低约63.51%、39.47 %和7.04 %。结论 对于合成数据集以及真实场景的深度数据集,本文方法均能有效处理存在于彩色边缘和深度不连续区域的不一致性问题,更好地保留深度边缘的不连续性。