Improving representation-based classification for robust face recognition

The sparse representation classification (SRC) method proposed by Wright et al. is considered as the breakthrough of face recognition because of its good performance. Nevertheless it still cannot perfectly address the face recognition problem. The main reason for this is that variation of poses, facial expressions, and illuminations of the facial image can be rather severe and the number of available facial images are fewer than the dimensions of the facial image, so a certain linear combination of all the training samples is not able to fully represent the test sample. In this study, we proposed a novel framework to improve the representation-based classification (RBC). The framework first ran the sparse representation algorithm and determined the unavoidable deviation between the test sample and optimal linear combination of all the training samples in order to represent it. It then exploited the deviation and all the training samples to resolve the linear combination coefficients. Finally, the classification rule, the training samples, and the renewed linear combination coefficients were used to classify the test sample. Generally, the proposed framework can work for most RBC methods. From the viewpoint of regression analysis, the proposed framework has a solid theoretical soundness. Because it can, to an extent, identify the bias effect of the RBC method, it enables RBC to obtain more robust face recognition results. The experimental results on a variety of face databases demonstrated that the proposed framework can improve the collaborative representation classification, SRC, and improve the nearest neighbor classifier.     

Virtual images inspired consolidate collaborative representation-based classification method for face recognition

Abstract

The collaborative representation-based classification method performs well in the field of classification of high-dimensional images such as face recognition. It utilizes training samples from all classes to represent a test sample and assigns a class label to the test sample using the representation residuals. However, this method still suffers from the problem that limited number of training sample influences the classification accuracy when applied to image classification. In this paper, we propose a modified collaborative representation-based classification method (MCRC), which exploits novel virtual images and can obtain high classification accuracy. The procedure to produce virtual images is very simple but the use of them can bring surprising performance improvement. The virtual images can sufficiently denote the features of original face images in some case. Extensive experimental results doubtlessly demonstrate that the proposed method can effectively improve the classification accuracy. This is mainly attributed to the integration of the collaborative representation and the proposed feature-information dominated virtual images.     

A supervised dimensionality reduction method-based sparse representation for face recognition

The sparse representation-based classification (SRC) method is a powerful tool to present high-dimensionality data and its superiority in many fields, especially in face recognition application has been proved. With sparsity appropriately harnessed, the SRC can solve face classification problems caused by varying expression, illumination as well as occlusion and disguise. However, face images as high-dimensionality data are usually noisy and the dimensionality is always larger than the number of training sample in real-world applications, which bring a disadvantage for the performance of SRC. Therefore, it is beneficial to perform dimensionality reduction (DR) before utilizing the SRC method. But most prevalent DR methods have no direct connection to SRC. In this paper, we proposed a supervised DR algorithm which suits SRC well and improves the discriminating ability in the low-dimensionality space. The proposed method utilizes the fisher discriminant criterion and low-dimensionality reconstructive restriction to extract the discriminating structure of data. The extensive experiments on public face databases verified the effectiveness of the supervised DR with the model of sparse representation.     

Combination of direct matching and collaborative representation for face recognition

Difficulties associated with the use of Buchdahl's retardation coefficients in image assessment are examined. It is shown that, by a series of approximations and corresponding transformations, the set of coordinates of transmitted rays from any object point can be expressed as a circular region perpendicular to the optical axis. Furthermore, it is shown that, under these transformations, the form of the retardation expansion remains constant and only the coefficients need be altered. These changes are independent of the field angle, but depend on the f-number of the system. The coefficients thus derived are field-independent in contrast to those specified by most authors. Expressions for the coefficients under each of the transformations introduced are presented. Also a brief discussion of the convergence of the retardation expansion is presented and the results indicate that the above approximations are sound over the region of convergence of the truncated aberration expansion of order eight.     

An improved SRC method based on virtual samples for face recognition

The sparse representation classifier (SRC) performs classification by evaluating which class leads to the minimum representation error. However, in real world, the number of available training samples is limited due to noise interference, training samples cannot accurately represent the test sample linearly. Therefore, in this paper, we first produce virtual samples by exploiting original training samples at the aim of increasing the number of training samples. Then, we take the intra-class difference as data representation of partial noise, and utilize the intra-class differences and training samples simultaneously to represent the test sample in a linear way according to the theory of SRC algorithm. Using weighted score level fusion, the respective representation scores of the virtual samples and the original training samples are fused together to obtain the final classification results. The experimental results on multiple face databases show that our proposed method has a very satisfactory classification performance.     

分块稀疏表示和2DPCA的人脸识别方法

稀疏表示提出了一种分块稀疏表示和二维主成分分析(2DPCA)的人脸识别方法.该方法应用了逐像素分块的与2DPCA技术相结合的方式,充分地考虑了图像中相邻的多个像素间的相关性.实验结果表明,其中提出的新算法具有可行性以及在识别精度上的优越性.进一步的研究还表明,所提出的分块识别的方法较之于以往传统算法在存在位置偏移、单色遮挡问题的人脸图像误判率上也有显著降低.     

共享空间基-逐类剩余空间基混合稀疏表示人脸识别算法

针对传统训练样本字典学习未利用类共有信息的不足,引入共享空间和与类别相关的剩余空间,提出了共享空间基-逐类剩余空间基混合稀疏表示人脸识别的算法。该算法首先提取训练样本主成分分析(PCA)特征,获取无标记的共享空间基及其重构样本得到类共有信息;然后结合原始样本得到差分训练集合,并引入类间差异信息构建逐类特异性剩余空间基;最后融合共享空间基和剩余空间基,利用残差判别函数完成模式分类。该方法不仅利用混合空间的正交特性,而且发挥剩余空间的鉴别能力和共享信息稀疏逼近的作用,使结构性字典和模式分类紧密结合。该方法的有效性,分别通过用AR、CMU PIE、Extended Yale B人脸数据库进行的实验得到验证。     

一种快速的基于稀疏表示的人脸识别算法

基于稀疏表示的人脸识别算法（SRC）识别率相当高,但是当使用l1范数求最优的稀疏表示时,大大增加了算法的计算复杂度,矩阵随着维度的增加,计算时间呈几何级别上升,该文提出利用拉格朗日算法求解矩阵的逆的推导思路,用一种简化的伪逆求解方法来代替l1范数的计算,可将运算量较高的矩阵求逆运算转变为轻量级向量矩阵运算,基于AR人脸库的实验证明,维度高的时候识别率高达97%,同时,计算复杂度和开销比SRC算法大幅度降低95%。     

Coded targets and hybrid grids for photogrammetric 3D digitisation of human faces

The three-dimensional (3D) measure of the human body is currently performed using mostly optical technologies. One of the most cost effective non-contact techniques is photogrammetry; its main disadvantage is the lack of automation because the correspondences between the same points in different images must be taken manually. In this paper the authors present a properly designed low-cost photogrammetric system for 3D scanning of human faces. Results are compared projecting onto the faces patterns composed by coded targets and mixed coded-uncoded targets.     

Weighted residual fusion with multi-modality features for high-resolution aerial scene classification

In scene-level classification of remote sensing, fusion of multi-feature can significantly boost the performance. However, most methods directly fuse the features of different modalities without considering the importance of each feature modality. Based on the above considerations, in this work, multi-modality features weighted residual fusion method is proposed. First, the extracted high-level and low-level features of the scene image are encoded into a unified feature representation. Then the reconstruction residuals of each modality of each scene class are calculated based on two representation-based classification, i.e. sparse representation (SR) and collaborative representation (CR). After fusing the weighted reconstruction residuals of these two modalities with SR and CR, the class label is assigned to the category with the smallest residual. We make extensive evaluations on two challenging remote sensing data sets. The comparison with the state-of-the-art methods demonstrates the effectiveness of our proposed method.     

Analysis of unsupervised learning techniques for face recognition

Face recognition has always been a potential research area because of its demand for reliable identification of a human being especially in government and commercial sectors, such as security systems, criminal identification, border control, etc. where a large number of people interact with each other and/or with the system. The last two decades have witnessed many supervised and unsupervised learning techniques proposed by different researchers for the face recognition system. Principal component analysis (PCA), self‐organizing map (SOM), and independent component analysis (ICA) are the most widely used unsupervised learning techniques reported by research community. This article presents an analysis and comparison of these techniques. The article also includes two SOM processing methods global SOM (GSOM) and local SOM (LSOM) for performance evaluation along with PCA and ICA. We have used two different databases for our analysis. The simulation result establishes the supremacy of GSOM in general among all the unsupervised techniques. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 261–267, 2010     

Compressed sensing with MCT and I(2D)2PCA processing for efficient face recognition

This article describes an effective human face recognition algorithm. Even though the principle component analysis (PCA) is one of the most common feature extraction methods, it is not suitable to implement a real‐time embedded system for face recognition because large amount of computational load and memory capacity are necessary. To overcome this problem, we employ the incremental two‐directional two‐dimensional PCA (I(2D)²PCA) which is a combination of the (2D)²PCA to demand much less computational complexity than the conventional PCA and the incremental PCA (IPCA) to adapt the eigenspace only by using a new incoming sample datum without reusing of all the previous trained data. Furthermore, the modified census transform (MCT), a local normalization method useful for real‐world application and implementation in an embedded system, is adopted to address robustness to illumination variations. To achieve better recognition accuracy with less computational load, the processed features are classified by the compressive sensing approach using ?²–minimization. Experimental results on the Yale Face Database B show that the described system using the ?²–minimization‐based classification method for input data processed by the I(2D)²PCA and the MCT provided efficient and robust face recognition. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 133–139, 2013     

Pattern recognition: Historical perspective and future directions

“What being walks sometimes on two feet, sometimes on three, and sometimes on four, and is weakest when it has the most?” —The Sphinx's Riddle Pattern recognition is one of the most important functionalities for intelligent behavior and is displayed by both biological and artificial systems. Pattern recognition systems have four major components: data acquisition and collection, feature extraction and representation, similarity detection and pattern classifier design, and performance evaluation. In addition, pattern recognition systems are successful to the extent that they can continuously adapt and learn from examples; the underlying framework for building such systems is predictive learning. The pattern recognition problem is a special case of the more general problem of statistical regression; it seeks an approximating function that minimizes the probability of misclassification. In this framework, data representation requires the specification of a basis set of approximating functions. Classification requires an inductive principle to design and model the classifier and an optimization or learning procedure for classifier parameter estimation. Pattern recognition also involves categorization: making sense of patterns not previously seen. The sections of this paper deal with the categorization and functional approximation problems; the four components of a pattern recognition system; and trends in predictive learning, feature selection using “natural” bases, and the use of mixtures of experts in classification. © 2000 John Wiley & Sons, Inc. Int J Imaging Syst Technol 11, 101–116, 2000     

Gabor特征结合Metaface学习的扩展稀疏表示人脸识别

为了克服人脸识别中存在的遮挡等闭塞问题,本文提出了Gabor特征结合Metaface学习的扩展稀疏表示人脸识别算法(GMFL)。考虑到Gabor局部特征对光照、表情和姿态等变化的鲁棒性,该算法首先提取图像的Gabor特征集;然后对Gabor特征集进行Metaface字典学习得到具有更强稀疏表示能力的新字典,同时引入Gabor闭塞字典来编码表示图像中的闭塞部分,并与新字典联合构造一组过完备字典基;最后利用过完备字典基求解稀疏系数重构样本,根据样本与重构样本之间的残差最小原则对人脸图像进行分类识别。在AR人脸库和FERET数据库上的实验结果验证了本文算法的可行性和有效性。     

基于多核学习的多阶次分数阶傅里叶变换域人脸识别

分数阶傅里叶变换是信号处理与分析的一个重要工具,通过将图像信号投影到不同角度的时频平面可以表征图像的内容信息,其在人脸识别任务中显示出很好的性能。但是分数阶傅里叶变换存在阶次选择的问题,即在没有先验知识的情况下,无法预先知道哪一个阶次的分数阶傅里叶变换域特征具有最好的判别性能。受机器学习中的多核学习理论启发,本文探讨了分数阶傅里叶变换中阶次选择问题和多核学习理论的联系,通过将不同阶次的分数阶傅里叶变化域特征的线性核矩阵作为多核学习网络的输入,结合支持向量机,交替优化更新多核网络中的系数和支持向量机的参数,自动学习多阶次分数阶傅里叶变换域特征的系数,实现多阶次分数阶傅里叶变换域特征的融合。将所提算法应用到人脸识别任务中,在ORL人脸数据集和扩展YaleB人脸数据集上的实验显示所提算法的可行性和有效性。     

Near-infrared and visible light image fusion algorithm for face recognition

In order to improve face recognition accuracy, we present a simple near-infrared (NIR) and visible light (VL) image fusion algorithm based on two-dimensional linear discriminant analysis (2DLDA). We first use two such schemes to extract two classes of face discriminant features of each of NIR and VL images separately. Then the two classes of features of each kind of images are fused using the matching score fusion method. At last, a simple NIR and VL image fusion approach is exploited to combine the scores of NIR and VL images and to obtain the classification result. The experimental results show that the proposed NIR and VL image fusion approach can effectively improve the accuracy of face recognition.     

Two-tier architecture for unconstrained handwritten character recognition

In this paper, we propose an approach that combines the unsupervised and supervised learning techniques for unconstrained handwritten numeral recognition. This approach uses the Kohonen self-organizing neural network for data classification in the first stage and the learning vector quantization (LVQ) model in the second stage to improve classification accuracy. The combined architecture performs better than the Kohonen self-organizing map alone. In the proposed approach, the collection of centroids at different phases of training plays a vital role in the performance of the recognition system. Four experiments have been conducted and experimental results show that the collection of centroids in the middle of the training gives high performance in terms of speed and accuracy. The systems developed also resolve the confusion between handwritten numerals.     

分布式光纤入侵信号检测与识别

分布式光纤声波传感(DAS)技术通过接收相干瑞利散射光的相位信息来探测声波或振动信号,具有灵敏度高、动态范围广等特性,可利用线性定量测量实现对信号的高保真还原.随着实际应用的需求不断提高,光纤入侵检测领域对事件的定位和识别提出了更高的要求,表现为对入侵事件的准确分类,因此将分布式光纤声波传感技术与模式识别(PR)技术相...     

利用语音的频谱空间特征进行汉语抗噪语音识别的方法

抗噪连续语音识别是当前汉语连续语音识别的重要研究领域。采用通过度量连续语音帧之间频谱的稳定性,将连续语音切分成份,再将切分结果(无论时间长短)变换为与时间无关的大小固定的频谱空间特征,通过与模板库进行比较实现语音识别。新的频谱空间特征,与语音时长无关,同时表现出较好的抗噪声能力。在特定人连续语音识别测试系统中,取得了不错的识别效果。     

一种基于自样本学习的人脸图像超分辨率复原算法

针对人脸图像超分辨率复原问题,提出了一种新的基于自样本学习的超分辨率复原算法.该算法从输入图像本身提取训练样本库,并采用矢量量化的方法对训练样本进行分类.再利用并行设计的多类预测器对每类样本进行学习训练,指导高频信息的估计重建.对来自输入图像本身的自样本训练集合和来自特定训练图像库的特定训练样本集合进行了对比研究.实验结果表明提出算法在图像重建质量和实现速度上都有很好的表现.