BGT: A blind image quality evaluator via gradient and texture statistical features

Blind image quality assessment (BIQA) aims to design a model that can accurately evaluate the quality of the distorted image without any information about its reference image. Previous studies have shown that gradients and textures of image is widely used in image quality evaluation tasks. However, few studies used the joint statistics of gradient and texture information to evaluate image quality. Considering the visual perception characteristics of the human visual system, we develop a novel general-purpose BIQA model via two sets of complementary perception features. Specifically, the joint statistical histograms of gradient and texture are extracted as the first set of features, and the second set of features is extracted using the local binary pattern (LBP) operator. After extracting two groups of complementary quality-aware features, the feature vectors are sent to the support vector regression machine to establish the nonlinear relationship between quality-aware features and quality scores. A large number of experiments on seven large benchmark databases show that the proposed BIQA model has higher accuracy, better generalization properties and lower computational complexity than the relevant state-of-the-art BIQA metrics.     

基于NSCT子带自适应Bayes阈值图像去噪方法

利用非下采样Contourlet变换（NSCT）平移不变性、多分辨率、多方向的优点,提出了一种基于非下采样Contourlet变换的子带自适应Bayes阈值图像去噪算法。该算法将源图像分解至NSCT变换域．能根据不同尺度、不同方向的子带能量,自适应调整去噪阈值。实验表明,与Contourlet多尺度阈值去噪、Conto...     

基于四阶相关系数的NSCT域红外与可见光图像融合

采用非下采样Contourlet变换(NSCT)模型提出了基于四阶相关系数的红外与可见光图像融合方法。首先对融合图像进行多尺度和多方向分解;对于低频分量,充分考虑红外和可见光图像物理特性的差异,采用基于区域平均梯度的融合策略;对高频分量采用四阶相关系数匹配策略来选择合适的高频系数;最后对融合后的系数进行NSCT逆变换得到融合图像。实验结果表明,该融合算法能更好地保留目标信息,同时也显著地提高了图像的信息量,在主观视觉效果和客观评价方面具有较好的融合性能。     

结合结构信息和亮度统计的无参考图像质量评价

基于非下采样Contourlet变换(Nonsubsampled Contourlet Transform,NSCT)子带系数间的结构相关性,本文提出了一种通用的无参考图像质量评价方法.首先,利用互信息分析NSCT子带系数间的相关性,确定出相关性比较强的子带系数;其次,分别计算这些子带系数间的结构信息比较算子,以此作为描述图像结构相关性的统计特征;进而,结合空间域亮度均值减损对比归一化(Mean Subtracted Contrast Normalized,MSCN)系数及其邻域系数的统计特征,分别构造相应的无参考图像质量评价模型和图像失真类型识别模型;最后,在LIVE等图像质量评价数据库上进行了大量的实验仿真.仿真结果表明,评价模型的评价结果与人类主观评价具有非常高的相关性,与当今主流评价算法相比非常具有竞争性.     

No-reference image quality assessment using statistical characterization in the shearlet domain

Image and video quality measurements are crucial for many applications, such as acquisition, compression, transmission, enhancement, and reproduction. Nowadays, no-reference (NR) image quality assessment (IQA) methods have drawn extensive attention because it does not rely on any information of original images. However, most of the conventional NR-IQA methods are designed only for one or a set of predefined specific image distortion types, which are unlikely to generalize for evaluating image/video distorted with other types of distortions. In order to estimate a wide range of image distortions, in this paper, we present an efficient general-purpose NR-IQA algorithm which is based on a new multiscale directional transform (shearlet transform) with a strong ability to localize distributed discontinuities. This is mainly based on distorted natural image that leads to significant variation in the spread discontinuities in all directions. Thus, the statistical property of the distorted image is significantly different from that of natural images in fine scale shearlet coefficients, which are referred to as ‘distorted parts’. However, some ‘natural parts’ are reserved in coarse scale shearlet coefficients. The algorithm relies on utilizing the natural parts to predict the natural behavior of distorted parts. The predicted parts act as ‘reference’ and the difference between the reference and distorted parts is used as an indicator to predict the image quality. In order to achieve this goal, we modify the general sparse autoencoder to serve as a predictor to get the predicted parts from natural parts. By translating the NR-IQA problem into classification problem, the predicted parts and distorted parts are utilized to form features and the differences between them are identified by softmax classifier. The resulting algorithm, which we name SHeArlet based No-reference Image quality Assessment (SHANIA), is tested on several database (LIVE, Multiply Distorted LIVE and TID2008) and shown to be suitable for many common distortions, consistent with subjective assessment and comparable to full-reference IQA methods and state-of-the-art general purpose NR-IQA algorithms.     

Unsupervised blind image quality assessment based on joint structure and natural scene statistics features

Compared with the widely used supervised blind image quality assessment (BIQA) models, unsupervised BIQA models require little prior knowledge for calculating the objective quality scores of distorted images. In this paper, we propose an unsupervised BIQA method that aims to achieve both good performance and generalization capability with low computational complexity. Carefully selected and extensive structure and natural scene statistics (NSS) features can better represent image quality. First, we employ phase congruency (PC) and finely selected gradient magnitude map and Laplacian of Gaussian response (GM-LOG) features to represent image structure information. Second, we calculate the local mean-subtracted and contrast-normalized (MSCN) coefficients and the Karhunen–Loéve transform (KLT) coefficients to represent the naturalness of the distorted images. Last, multivariate Gaussian (MVG) model with joint features extracted from both the pristine images and the distorted images is adopted to calculate the objective image quality. Extensive experiments conducted on nine IQA databases demonstrate that the proposed method achieves better performance than the state-of-the-art BIQA methods.     

基于非采样Contourlet变换的红外与可见光图像融合方法

针对同一场景的红外与可见光图像融合,提出了一种基于非采样Contourlet变换（NSCT）和改进的脉冲耦合神经网络（IPCNN）的图像融合新算法。首先利用NSCT对图像进行多尺度、多方向稀疏分解,然后针对各带通方向高频子带系数的选择,提出了一种应用IPCNN计算图像匹配度的融合策略。实验结果表明,该算法能够很好地将红外图像与可见光图像中的重要信息提取并注入到融合图像中,与其他方法相比较,取得了更好的融合效果,提高了融合图像的质量。     

基于Shearlet变换的多聚焦图像融合方法

为提高多聚焦图像的融合效果,利用Shearlet变换具有多尺度多方向的特性,文中提出了一种基于Shearlet变换的图像融合算法。针对待融合图像进行Shearlet变换,得到低频子带系数和不同尺度不同方向的高频子带系数;对低频子带系数取分解系数区域能量高的系数,高频子带系数采用区域能量和区域清晰度以及区域方差相结合,采用多判别法得到融合系数,并最终进行Shearlet逆变换得到融合图像。结果表明,在主观视觉效果和客观评价指标上此算法优于其他融合算法     

shearlet变换和区域特性相结合的图像融合

为了提高多模医学图像或多聚焦图像的融合性能,结合shearlet变换能够捕捉图像细节信息的性质,提出了一种基于shearlet变换的图像融合算法。首先,用shearlet变换将已精确配准的两幅原始图像分解,得到低频子带系数和不同尺度不同方向的高频子带系数。低频子带系数使用改进的加权融合算法,用平均梯度来计算加权参量,以此来改善融合图像轮廓模糊度高的问题,高频子带系数采用区域方差和区域能量相结合的融合规则,以得到丰富的细节信息。最后,进行shearlet逆变换得到融合图像。结果表明,此算法在主观视觉效果和客观评价指标上优于其它融合算法。     

Bayesian-Based Speckle Suppression for SAR Image Using Contourlet Transform

A novel and efficient speckle noise reduction algorithm based on Bayesian contourlet shrinkage using contourlet transform is proposed.First,we show the sub-band decompositions of SAR images using contourle transforms,which provides sparse representation at both spatial and directional resolutions.Then,a Bayesian contourlet shrinkage factor is applied to the decomposed data to estimate the best value for noise-free contourle coefficients.Experimental results show that compared with conventional wavelet despeckling algorithm,the proposed algorithm can achieve an excellent balance between suppresses speckle effectively and preserve image details,and the significant information of origina image like textures and contour details is well ma intained.     

基于Contourlet变换和IPCNN的融合算法及其在可见光与红外线图像融合中的应用

针对多传感器图像融合这一图像处理领域中的研究热点问题,提出了一种基于Contourlet变换和IPCNN的融合方法.该融合方法首先利用Contourlet对输入图像进行多尺度、多方向稀疏分解,准确地捕获图像中的二维或高维奇异信息,然后在Contourlet域充分利用IPCNN的同步激发特性,进行基于IPCNN的融合策略设计,提高了融合效果.仿真结果表明,该算法具有很好的融合效果.     

基于非采样Contourlet变换的图像融合算法

针对同一场景的红外与可见光图像融合问题,提出了一种基于非采样Contourlet变换的图像融合方法。该方法对图像经非采样Contourlet变换后的低频系数采用基于图像物理特征的“加权平均”融合方法;对于高频系数采用基于局部对比度与空间频率比相结合的系数融合方法。为验证本文算法的有效性,对红外与可见光图像进行了融合实验,实验结果表明该方法相对于传统的简单融合方法以及基于区域能量的融合方法能得到具有更好视觉效果和更优量化指标的融合图像。      

基于方向区域的NSCT图像融合算法

提出一种新的基于方向区域的NSCT图像融合算法。算法首先对源图像进行NSCT分解,获得不同方向的高低频子带。其次对高低频系数,根据不同分解层的方向特性,按方向区域能量的规则进行融合。最后,通过反变换获得融合图像。该方法既保留了Contourlet变换方法的多尺度多方向特性,又具有移不变性。实验结果表明,提出的算法有效可行,对比常用的区域融合算法,获得了更好的融合效果。     

基于NSCT及熵的旋转不变彩色图像检索算法

为了解决图像在转载过程中所产生的旋转变化和尺 度变化对检索的影响,根据熵的对称性,提出了基于NSCT及熵的旋转不变图像检索算法。首 先,利用非下采样轮廓波变换(NSCT)对图像进行多尺度、多方向分解,对不同尺度、同方 向的高频方向子带求多尺度积,以减小尺度变 化和噪声对检索效率的影响;然后,考虑到图像旋转后各方向子带在整幅图像中的能量比例 不会发生变化, 将各方向子带的能量比例作为概率矢量,各方向子带的粗糙度作为权值求取图像的加权信息 熵,作为具 有旋转不变性的图像纹理特征,利用矩提取图像的颜色和形状特征;最后,归一化3种特征 来比较两幅图 像的相似性。性能测试表明,本文所提出的方法对旋转变换鲁棒性强,且具有很高的查准率 和查全率。     

基于Contourlet系数局部特征的选择性遥感图像融合算法

为了使融合后的多光谱图像在显著提高空间分辨率的同时,尽可能多地保持原始多光谱特性,提出了一种基于Contourlet变换系数局部特征的选择性遥感图像融合方法。根据多光谱和全色图像融合过程中Contourlet变换后的低频和高频部分融合目的的不同,对得到的近似和各层各方向的细节分量分别运用窗口邻域移动模板逐一计算相应区域Contourlet系数阵的不同局部特征量,然后选择适当的准则,对图像的近似和细节分量分别应用不同的策略在Contourlet系数域内进行选择性融合,通过Contourlet和亮度-色调-饱和度(IHS)逆变换得到融合的高分辨率多光谱图像。采用Landsat TM多光谱和SPOT全色图像进行的融合实验结果表明:提出的算法在显著提高空间分辨率的同时,又能很好地保持原始图像的光谱特征,并优于传统的融合方法。     

非抽样双树复小波域的BPP-NMF图像融合

提出了一种非抽样双树复小波变换（UDT-CWT）与基于块主元旋转的非负矩阵分解（BPP-NMF）相结合的多聚焦图像融合算法。利用UDT-CWT具有完美的平移不变性及良好的方向选择性,首先对图像进行多尺度、多方向分解并得到低频子带和高频子带系数;然后对低频子带系数采用块主元旋转的非负矩阵分解的融合策略,高频系数则选用高斯加权区域能量与区域标准差一致性选择的融合准则。最后对融合后的系数进行UDT-CWT逆变换得到重构图像。选用多组多聚焦图像进行融合并对融合结果进行主观视觉、客观方面的评价。试验结果表明,该融合算法不仅具有良好的视觉效果,同时在客观评价指标也优于一般的融合策略,验证了该算法的有效性。     

Stereo matching cost computation based on nonsubsampled contourlet transform

A new matching cost computation method based on nonsubsampled contourlet transform (NSCT) for stereo image matching is proposed in this paper. Firstly, stereo image is decomposed into high frequency sub-band images at different scales and along different directions by NSCT. Secondly, by utilizing coefficients in high frequency domain and grayscales in RGB color space, the computation model of weighted matching cost between two pixels is designed based on the gestalt laws. Lastly, two types of experiments are carried out with standard stereopairs in the Middlebury benchmark. One of the experiments is to confirm optimum values of NSCT scale and direction parameters, and the other is to compare proposed matching cost with nine known matching costs. Experimental results show that the optimum values of scale and direction parameters are respectively 2 and 3, and the matching accuracy of the proposed matching cost is twice higher than that of traditional NCC cost.     

基于无抽样Contourlet变换的图像增强方法

为了有效增强图像的细节信息,研究了基于无抽样Contourlet变换的图象增强方法。首先将待增强图像进行无抽样Contourlet变换,然后使用映射函数对无抽样Contourlet系数进行增强处理,最后进行无抽样Contourlet反变换得到增强后的图像。实验结果表明,该方法可以有效增强图像的微弱边缘信息。     

基于整数小波变换的Wiener插值算法

小波变换中高低分辨率子带之间的相似性使得利用小波变换进行图像插值的方法成为可能.根据数字图像信号的特点,分析了小波变化后各个子带信号的特点,提出了基于整数小波变换的Wiener插值算法.用Wiener自适应滤波器训练得到插值滤波系数,同时结合既符合图像性质又能减小运算量的整数双正交小波基对图像插值.结果得到较高的信噪比和较好的主观视觉效果.平均峰值信噪比比传统的双线性插值法提升了2.4dB.     

椭圆方向窗与新轮廓波应用于多聚焦融合算法研究

针对光学显微镜景深扩展中的多聚焦图像融合问题,提出了一种基于方向特性的新轮廓波域多聚焦图像融合算法。该算法首先对图像进行新轮廓波变换(New Contourlet Transform with Sharp Frequency Localization,NCT-SFL),分解得到不同尺度、不同方向的高低频系数,低频系数融合使用算术平均法,高频系数融合分为两步:先采用改进拉普拉斯能量和(Sum Modified Laplacian,SML) 提取特征值;然后定义新的与方向分解一一对应的椭圆方向窗,在确定的椭圆窗参数下,对提取的特征值进行累加并以此为依据对高频系数进行融合,最后通过反新轮廓波变换得到融合图像。在实验部分用定义的新的客观评价指标互结构信息(Mutual Structural Information,MSI)对融合算法进行了评价,结果表明:对多聚焦图像本文所提方法比新轮廓波域方形窗算法MSI提高了2.94%,比Contourlet域方形窗与椭圆窗算法MSI分别提高了10.44%和8.56%。说明本文方法能提取源图像中更多的清晰信息到融合图像,是一种有效的景深扩展手段。