Discriminative dictionary learning algorithm based on sample diversity and locality of atoms for face recognition

Dictionary learning is one of the most important algorithms for face recognition. However, many dictionary learning algorithms for face recognition have the problems of small sample and weak discriminability. In this paper, a novel discriminative dictionary learning algorithm based on sample diversity and locality of atoms is proposed to solve the problems. The rational sample diversity is implemented by alternative samples and new error model to alleviate the small sample size problem. Moreover, locality can leads to sparsity and strong discriminability. In this paper, to enhance the dictionary discrimination and to reduce the influence of noise, the graph Laplacian matrix of atoms is used to keep the local information of the data. At the same, the relational theory is presented. A large number of experiments prove that the proposed algorithm can achieve more high performance than some state-of-the-art algorithms.     

字典学习优化判别性降维的鲁棒人脸识别

针对现有的人脸识别算法由于光照、表情、姿态、面部遮挡等变化而严重影响识别性能的问题,提出了基于字典学习优化判别性降维的鲁棒人脸识别算法。首先,利用经典的特征提取算法PCA初始化降维投影矩阵;然后,计算字典和系数,通过联合降维与字典学习使得投影矩阵和字典更好地相互拟合;最后,利用迭代算法输出字典和投影矩阵,并利用经l2-范数正则化的分类器完成人脸的识别。在扩展YaleB、AR及一个户外人脸数据库上的实验验证了本文算法的有效性及鲁棒性,实验结果表明,相比几种线性表示算法,本文算法在处理鲁棒人脸识别时取得了更高的识别率。     

Sparse representation for face recognition by discriminative low-rank matrix recovery

This paper proposes a discriminative low-rank representation (DLRR) method for face recognition in which both the training and test samples are corrupted owing to variations in occlusion and disguise. The proposed method extends the sparse representation-based classification algorithm by incorporating the low-rank structure of data representation. The DLRR algorithm recovers a clean dictionary with enhanced discrimination ability from the corrupted training samples for sparse representation. Simultaneously, it learns a low-rank projection matrix to correct corrupted test samples by projecting them onto their corresponding underlying subspaces. The dictionary elements from different classes are encouraged to be as independent as possible by regularizing the structural incoherence of the original training samples. This leads to a compact representation of a corrected test sample by a linear combination of more dictionary elements from the corrected class. The experimental results on benchmark databases show the effectiveness and robustness of our face recognition technique.     

融合协作表达和重构判别分析的数据降维算法

数据降维是处理高维数据的有效手段。子空间学 习算法由于其计算量小,性能较为出 色而广泛应用于模式识别等领域,传统的子空间学习算法均可归纳为图嵌入算法框架中。稀 疏表达是近年来的一个研究热点,并广泛应用于信号处理和模式识别等领域,但计算复杂度 较高。在稀疏表达的基础上,研究者提出了协作表达。相比稀疏表达,协作表达算法由于其 有一个闭式解,因而计算量较小且判别性能较好,可以看成是数据表达的一种有效方法。本 文从协作表达的角度来解释图嵌入算法,将图嵌入算法看作是一类回归模型。通过最小化类 内重构误差散度的同时最大化类间重构误差散度,提出了一种新的图嵌入算法,即重构判别 分析,并将它应用于该回归模型中,然后将问题归结为一广义的特征值问题,算法在某种程 度上能有效避免子空间学习过程中矩阵的奇异性问题。在人脸识别上的实验验证了算法的正 确性和有效性。     

基于判别性降维的字典学习在人脸识别中的应用

针对目前大多数人脸识别方法只能单独实施降维或者字典学习而不能完全利用训练样本判别信息的问题,提出了基于判别性降维的字典学习方法,通过联合降维与字典学习使得投影矩阵和字典更好地相互拟合,从而可以获得更高效的人脸分类系统。所提方法的有效性在AR及MPIE两大通用人脸数据库上得到了验证,实验结果表明,相比于几种先进的线性表示方法,所提算法取得了更高的识别率,特别当训练样本数很少的时候,识别效果更佳。     

一种基于局部拓扑与l1/2范数的解析字典分类的人群事件检测

所提方案在传统解析字典算法基础上,加入局部拓扑项用以描述数据之间的结构信息,同时用l_1/2范数代替 l₁范数作为稀疏约束,从而提高表示系数的稀疏度。在特征提取上,融合了包含丰富运动信息的相互作用力直方图与包含纹理信息的梯度方向直方图,然后用改进的字典对特征数据进行训练,最后通过计算测试样本在该字典下的重构误差来判断测试样本是否为异常样本。在标准行为库UMN（University of Minnesota）数据库上进行的实验证实了算法具有较高的性能。与传统的算法相比,提出的改进的解析字典分类算法在针对人群异常事件中取得了更为有效的检测。     

Face recognition using position-dictionaries and region covariance feature

In this paper, a new sparsity formulation called position-dictionary based sparse representation is developed for frontal face recognition. Different from the sparse representation based classification (SRC) method and the Gabor-feature based SRC (GSRC) method which both employ a global dictionary to decompose image patches, the proposed method constructs a position-dictionary for each location using training patches in the corresponding location since they resemble each other and are more likely to favor the same atoms. Sparse coefficients of each position-patch can be obtained by solving an \(l_{1}\) -norm minimization problem. For each face image, sparse coefficients of position-patches are pooled to construct a discriminative upper level feature to represent face image. PCA is used to perform dimension reduction. Each testing sample is represented as a sparse linear combination of all training samples, and recognition is accomplished by evaluating which class of training samples leads to the minimum reconstruction error. We compared the proposed method with SRC and GSRC method on three benchmark face databases. Experimental results show that the proposed method achieves higher recognition rates and is robust to a certain degree of occlusions.     

Learning Sparse Overcomplete Codes for Images

Images can be coded accurately using a sparse set of vectors from a learned overcomplete dictionary, with potential applications in image compression and feature selection for pattern recognition. We present a survey of algorithms that perform dictionary learning and sparse coding and make three contributions. First, we compare our overcomplete dictionary learning algorithm (FOCUSS-CNDL) with overcomplete independent component analysis (ICA). Second, noting that once a dictionary has been learned in a given domain the problem becomes one of choosing the vectors to form an accurate, sparse representation, we compare a recently developed algorithm (sparse Bayesian learning with adjustable variance Gaussians, SBL-AVG) to well known methods of subset selection: matching pursuit and FOCUSS. Third, noting that in some cases it may be necessary to find a non-negative sparse coding, we present a modified version of the FOCUSS algorithm that can find such non-negative codings. Efficient parallel implementations in VLSI could make these algorithms more practical for many applications.     

Sparse representation for robust face recognition by dictionary decomposition

Sparse representation-based classification (SRC) method has gained great success in face recognition due to its encouraging and impressive performance. However, in SRC the data used to train or test are usually corrupted, and hence the performance is affected. This paper proposes a robust face recognition approach by means of learning a class-specific dictionary and a projection matrix. Firstly, the training data are decomposed into class-specific dictionary, non-class-specific dictionary, and sparse error matrix. Secondly, in order to correct the corrupted test data, the data are projected onto their corresponding underlying subspace, and a projection matrix between the original training data and the class-specific dictionary is learned. Then, the features of the class-specific dictionary and the corrected test data are extracted by using Eigenface method. Finally, the SRC is performed to classify. Extensive experiments conducted on publicly available data sets show that the proposed algorithm performs better than some state-of-the-art methods.     

原子-分子字典结合的联合扩展加权稀疏表示人脸识别算法

针对训练样本字典学习仅包含全局信息、缺乏局部信息的不足,引入与类别相关的原子字典, 提出基于原子与分子字典联合扩展的加权稀疏表示人脸识别方法。首先,对各类训练样本进行PCA学习,得到带标记的训练样本基,构造PCA基原子字典,同时将训练样本字典作为分子字典。进而,利用原子字典与分子字典结合得到扩展字典模型。测试时,根据测试样本与扩展字典基之间的距离进行加权得到与当前测试样本关联的重构字典集,最后对测试样本稀疏重构,利用残差进行分类判别。为验证本文方法有效性,分别在AR、Georgia Tech和CMU PIE人脸数据库上进行实验。      

Object tracking using discriminative sparse appearance model

Object tracking based on sparse representation formulates tracking as searching the candidate with minimal reconstruction error in target template subspace. The key problem lies in modeling the target robustly to vary appearances. The appearance model in most sparsity-based trackers has two main problems. The first is that global structural information and local features are insufficiently combined because the appearance is modeled separately by holistic and local sparse representations. The second problem is that the discriminative information between the target and the background is not fully utilized because the background is rarely considered in modeling. In this study, we develop a robust visual tracking algorithm by modeling the target as a model for discriminative sparse appearance. A discriminative dictionary is trained from the local target patches and the background. The patches display the local features while their position distribution implies the global structure of the target. Thus, the learned dictionary can fully represent the target. The incorporation of the background into dictionary learning also enhances its discriminative capability. Upon modeling the target as a sparse coding histogram based on this learned dictionary, our tracker is embedded into a Bayesian state inference framework to locate a target. We also present a model update scheme in which the update rate is adjusted automatically. In conjunction with the update strategy, the proposed tracker can handle occlusion and alleviate drifting. Comparative results on challenging benchmark image sequences show that the tracking method performs favorably against several state-of-the-art algorithms.     

一种基于相关性投影的人脸性别分类算法

针对于人脸图像检测的有效利用性,为了提高其检测的性能,提出一种新的基于 监督学习的优化相关性投影(ORP)人脸性别分类算法,并将其应用到基 于Eigenface算法与Fisherface算法的人脸识别中,以及应 用WPCA到基于PGA的性别分类中。本文算法首先基于带权主成分分析(WPCA)算法来降低脸部 维度,将脸部特征提取出;然后,对其进行优化,同时 计算ORP的误差函数;最后,最小化脸部ORP误差函数,计算特征向量的 欧式距离,进行人脸性别分类。将提出方法与 传统方法进行对比,在FERET数据库上进行了实验,证明了本文方法的有效性,获得了优 于传统方法的识别率。     

一种多算法融合的人脸识别方法研究

针对人脸识别技术易受光照、姿态、表情等影响 ,为了增强人脸识别算法的鲁棒性,提出首先采用 LBP算法提取人脸图像的局部纹理特征,使用PCA算法将高维的空间人脸图像投影到低维的 特征空间,使 用LDA算法利用人脸类别标签信息寻找最优的投影向量,实现了人脸图像维度进一步地压缩 ,最后使用SVM 分类器分类匹配得到识别结果。分别使用ORL和Yale人脸数据库验证了算法的有效性,实 验结果表明,文 中该方法具有良好的识别性能,与其它的识别算法相比,识别率有了较大的提高。     

一种基于局部排序的约束稀疏编码的图像分类方法

图像分类作为计算机视觉分析领域一个重要的研究方向,其分类性能很大程度上取决于图像的特征表示.为了能够更好地进行图像分类,本文提出了一种基于局部约束稀疏编码的神经气算法（Neural Gas based Locality-constrained Sparse Coding,NGLSC）用来实现图像分类.引入局部排序适配器作为距离正则化约束项已经应用在神经气（Neural Gas,NG）的算法矢量量化中,旨在通过软竞争学习算法来弥补K均值聚类（K-means）算法的不足.在稀疏编码阶段此算法可求解得到封闭解.此外,字典更新一般由目标函数的误差项来决定,已有一些经典的算法采用这种方式更新字典.本文使用ORL数据库和COIL20数据库将所提出算法和现有算法局部约束线性编码（Locality-constrained Linear Coding,LLC）,脸元数据学习方法（Metaface Learning,MFL）进行比较.实验结果证明本文所提出的算法在图像分类上准确率可达95%以上.可以看出,本文为计算机视觉图像分类工作提供了一种有价值的解决思路.     

基于核协同表示与鉴别投影的辐射源调制识别

针对辐射源识别中的特征稳定性不高和低信噪比环境适应性不足等问题,提出了一种基于二次时频分布、核协同表示与鉴别投影的识别方法.首先,通过时频变换、稀疏域降噪和二次特征提取的预处理算法降低噪声干扰和特征冗余,以获取高稳定性的二次时频分布特征;然后,采用核协同表示和鉴别投影思想进行降维学习和字典学习,以提升数据低维表征和类间鉴别能力;最后,通过离线训练完成系统优化并用于分类验证.仿真结果表明,二次时频分布特征具备较高稳定性,识别方法具备较强鲁棒性、时效性和适应性;当信噪比为-10dB时,该方法对8类辐射源信号的整体平均识别率达到96.88%.     

Histopathological image classification through discriminative feature learning and mutual information-based multi-channel joint sparse representation

Histopathological image classification is a very challenging task because of the biological heterogeneities and rich geometrical structures. In this paper, we propose a novel histopathological image classification framework, which includes the discriminative feature learning and the mutual information-based multi-channel joint sparse representation. We first propose a stack-based discriminative prediction sparse decomposition (SDPSD) model by incorporating the class labels information to predict deep discriminant features automatically. Subsequently, a mutual information-based multi-channel joint sparse model (MIMCJSM) is presented to jointly encode the common component and particular components of the discriminative features. Especially, the main advantage of the MIMCJSM is the construction of a joint dictionary using a mutual information criterion, which contains a common sub-dictionary and three particular sub-dictionaries. Based on the joint dictionary, the MIMCJSM captures the relationship of multi-channel features, which can improve discriminative ability of joint sparse representation coefficients. Finally, the joint sparse representation coefficients of different levels can be aggregated using the spatial pyramid matching (SPM) model, and the linear support vector machine (SVM) is used as the classifier. Experimental results on ADL and BreaKHis datasets demonstrate that our proposed framework consistently performs better than popular existing classification frameworks. Additionally, it can show promising strong-robustness performance for histopathological image classification.     

基于低秩表示的鲁棒判别特征子空间学习模型

特征子空间学习是图像识别及分类任务的关键技术之一,传统的特征子空间学习模型面临两个主要的问题。一方面是如何使样本在投影到特征空间后有效地保持其局部结构和判别性。另一方面是当样本含噪时传统学习模型所发生的失效问题。针对上述两个问题,该文提出一种基于低秩表示(LRR)的判别特征子空间学习模型,该模型的主要贡献包括:通过低秩表示探究样本的局部结构,并利用表示系数作为样本在投影空间的相似性约束,使投影子空间能够更好地保持样本的局部近邻关系;为提高模型的抗噪能力,构造了一种利用低秩重构样本的判别特征学习约束项,同时增强模型的判别性和鲁棒性;设计了一种基于交替优化技术的迭代数值求解方案来保证算法的收敛性。该文在多个视觉数据集上进行分类任务的对比实验,实验结果表明所提算法在分类准确度和鲁棒性方面均优于传统特征学习方法。     

自适应通用学习框架改进FLDA的人脸识别

针对传统的Fisher线性判别分析(FLDA)算法在处理单训练样本人脸识别时由于类内散布矩阵为零而不能进行特征提取的问题,提出了一种基于自适应通用学习框架改进FLDA的人脸识别算法。首先选取一个合适的通用训练样本集,计算其类内散布矩阵和样本平均向量;然后,利用双线性表示算法预测单训练样本的类内、类间散布矩阵,巧妙地解决了单训练样本类内散布矩阵为零的问题;最后,利用Fisher线性判别分析进行特征提取,同时借助于最近邻分类器完成人脸的识别。在Yale及FERET两大通用人脸数据库上的实验验证了所提算法的有效性及可靠性,实验结果表明,相比其他几种较为先进的单样本人脸识别算法,所提算法取得了更好的识别效果。     

Semi-Supervised Bilinear Subspace Learning

Recent research has demonstrated the success of tensor based subspace learning in both unsupervised and supervised configurations (e.g., 2-D PCA, 2-D LDA, and DATER). In this correspondence, we present a new semi-supervised subspace learning algorithm by integrating the tensor representation and the complementary information conveyed by unlabeled data. Conventional semi-supervised algorithms mostly impose a regularization term based on the data representation in the original feature space. Instead, we utilize graph Laplacian regularization based on the low-dimensional feature space. An iterative algorithm, referred to as adaptive regularization based semi-supervised discriminant analysis with tensor representation (ARSDA/T), is also developed to compute the solution. In addition to handling tensor data, a vector-based variant (ARSDA/V) is also presented, in which the tensor data are converted into vectors before subspace learning. Comprehensive experiments on the CMU PIE and YALE-B databases demonstrate that ARSDA/T brings significant improvement in face recognition accuracy over both conventional supervised and semi-supervised subspace learning algorithms.     

PCA-based dictionary building for accurate facial expression recognition via sparse representation

Sparse representation is a new approach that has received significant attention for image classification and recognition. This paper presents a PCA-based dictionary building for sparse representation and classification of universal facial expressions. In our method, expressive facials images of each subject are subtracted from a neutral facial image of the same subject. Then the PCA is applied to these difference images to model the variations within each class of facial expressions. The learned principal components are used as the atoms of the dictionary. In the classification step, a given test image is sparsely represented as a linear combination of the principal components of six basic facial expressions. Our extensive experiments on several publicly available face datasets (CK+, MMI, and Bosphorus datasets) show that our framework outperforms the recognition rate of the state-of-the-art techniques by about 6%. This approach is promising and can further be applied to visual object recognition.