整合原始人脸图像和其虚拟样本的人脸分类算法

人脸识别作为最具吸引力的生物识别技术之一,由于会受到不同的照明条件、面部表情、姿态和环境的影响,仍然是一个具有挑战性的任务.众所周知,一幅人脸图像是对人脸的一次采样,它不应该被看作是脸部的绝对精确表示.然而在实际应用中很难获得足够多的人脸样本.随着稀疏表示方法在图像重建问题中的成功应用,研究人员提出了一种特殊的分类方法,即基于稀疏表示的分类方法.受此启发,提出了在稀疏表示框架下的整合原始人脸图像和虚拟样本的人脸分类算法.首先,通过合成虚拟训练样本来减少面部表示的不确定性.然后,在原始训练样本和虚拟样本组成的混合样本中通过计算来消除对分类影响较小的类别和单个样本,在系数分解的过程中采用最小误差正交匹配追踪(Error-Constrained Orthogonal Matching Pursuit,OMP)方法,进而选出贡献程度大的类别样本并进行分类.实验结果表明,提出的方法不仅能获得较高的人脸识别的精度,而且还具有更低的计算复杂性.     

Enhancing sparsity via full rank decomposition for robust face recognition

In this paper, we propose a fast and robust face recognition method named enhancing sparsity via full rank decomposition. The proposed method first represents the test sample as a linear combination of the training data as the same as sparse representation, then make a full rank decomposition of the training data matrix. We obtain the generalized inverse of the training data matrix and then solve the general solution of the linear equation directly. For obtaining the optimum solution to represent the test sample, we use the least square method to solve it. We classify the test sample into the class which has the minimal reconstruction error. Our method can solve the optimum solution of the linear equation, and it is more suitable for face recognition than sparse representation classifier. The extensive experimental results on publicly available face databases demonstrate the effectiveness of the proposed method for face recognition.     

Collaborative representation with reduced residual for face recognition

Collaboration representation-based classification (CRC) was proposed as an alternative approach to the sparse representation method with similar efficiency. The CRC is essentially a competition scheme for the training samples to compete with each other in representing the test sample, and the training class with the minimum representation residual from the test sample wins the competition in the classification. However, the representation error is usually calculated based on the Euclidean distance between a test sample and the weighted sum of all the same-class samples. This paper exploits alternative methods of calculating the representation error in the CRC methods to reduce the representation residual in a more optimal way, so that the sample classes compete with each other in a closer range to represent the test sample. A large number of face recognition experiments on three face image databases show that the CRC methods with optimized presentation residual achieve better performance than the original CRC, and the maximum improvement in classification accuracy is up to 12 %.     

A singular value decomposition representation based approach for robust face recognition

In the field of face recognition, sparse representation based classification (SRC) and collaborative representation based classification (CRC) have been widely used. Although both SRC and CRC have shown good classification results, it is still controversial whether it is sparse representation or collaborative representation that helps face recognition. In this paper, a new singular value decomposition based classification (SVDC) is proposed for face recognition. The proposed approach performs SVD on the training data of each class, and then determines the class of a test sample by comparing in which class of singular vectors it can be better represented. Experimental results on Yale B, PIE and UMIST datasets show that the proposed method achieves better recognition performance compared with several existing representation based classification algorithms. In addition, by adding Gaussian noise and Salt pepper noise to these datasets, it is proved that SVDC has better robustness. At the same time, the experimental results show that the recognition accuracy of the method acting on the training samples constructed by each class is higher than that of the method acting on the training sets constructed by all classes.

     

一种新的拓展稀疏人脸识别算法

近几年来,基于稀疏表示分类是一个备受关注的研究热点。如果每类训练样本较充分,该类方法可以取得比较好的识别效果。当训练样本比较少时,它的分类效果可能就不理想。拓展的稀疏分类算法可以较好的解决这一问题,它在表示测试样本时,引入了训练样本的类内变量矩阵,利用它和训练样本集来表示测试样本,从而提高了人脸识别率。然而,该算法并没有考虑训练样本在表示测试样本中所起的作用,即所有训练样本的权重都等于1。本文采用高斯核距离对训练样本加权,提出用加权的训练样本和类内散度矩阵来共同表示测试样本,即基于加权的拓展识别算法。实验证明所提算法能够取得更好的人脸识别效果。     

基于稀疏表示和弹性网络的人脸识别

由于稀疏表示方法在人脸分类算法中的成功使用,在此基础上提出了一种更为有效的基于稀疏表示（SRC）和弹性网络相结合的分类方法。为了加强样本间的协作表示能力以及增强处理强相关性变量数据的能力,基于迭代动态剔除机制,提出一种结合弹性网络的稀疏分解方法。通过采用训练样本的线性组合来表示测试样本,并运用迭代机制从所有样本中剔除对分类贡献度较小的类别和样本,采用Elastic Net算法来进行系数分解,从而选择出对分类贡献度较大的样本和类别,最后根据计算相似度对测试样本进行分类。在ORL、FERET和AR三个数据集进行了许多实验,实验结果显示算法识别率分别达到了98.75%、86.62%、99.72%,表明了所提算法的有效性。所提算法相比LASSO和SRC-GS等方法,在系数分解过程中增强了处理高维小样本和强相关性变量数据的能力,突出了稀疏约束在该算法中的重要性,具有更高的准确性和稳定性,能够更加有效地适用于人脸分类。     

Bidirectional representation for face recognition across pose

Conventional representation methods try to express the test sample as a weighting sum of training samples and exploit the deviation between the test sample and the weighting sum of the training samples from each class (also referred to as deviation between the test sample and each class) to classify the test sample. In particular, the methods assign the test sample to the class that has the smallest deviation among all the classes. This paper analyzes the relationship between face images under different poses and, for the first time, devises a bidirectional representation method-based pattern classification (BRBPC) method for face recognition across pose. BRBPC includes the following three steps: the first step uses the procedure of conventional representation methods to express the test sample and calculates the deviation between the test sample and each class. The second step first expresses the training sample of a class as a weighting sum of the test sample and the training samples from all the other classes and then obtains the corresponding deviation (referred to as complementary deviation). The third step uses the score-level fusion to integrate the scores, that is, deviations generated from the first and second steps for final classification. The experimental results show that BRBPC classifies more accurately than conventional representation methods.     

基于鉴别性低秩表示及字典学习的鲁棒人脸识别算法

针对人脸识别中的图像存在噪声等情况,提出基于鉴别性低秩表示及字典学习的算法。使用鉴别性低秩子空间恢复算法(discriminative low-rank representation, DLRR)获得类别间尽可能独立且干净的训练样本,然后通过引入基于Fisher准则的字典学习(Fisher Discrimination Dictionary Learning, FDDL)方法得到结构化字典,其子字典对对应的类有较好的表示能力,约束编码系数具有较小类内散列度和较大类间散列度。最后对测试样本稀疏线性表示时正确类别的样本贡献更大。在标准人脸数据库上的实验结果表明该算法有较好性能。     

利用CNN和PCA约束优化模型实现稀疏表示分类

目的 传统的稀疏表示分类方法运用高维数据提升算法的稀疏分类能力,早已引起了广泛关注,但其忽视了测试样本与训练样本间的信息冗余,导致了不确定性的决策分类问题。为此,本文提出一种基于卷积神经网络和PCA约束优化模型的稀疏表示分类方法（EPCNN-SRC）。方法 首先通过深度卷积神经网络计算,在输出层提取对应的特征图像,用以表征原始样本的鲁棒人脸特征。然后在此特征基础上,构建一个PCA（principal component analysis）约束优化模型来线性表示测试样本,计算对应的PCA系数。最后使用稀疏表示分类算法重构测试样本与每类训练样本的PCA系数来完成分类。结果 本文设计的分类模型与一些典型的稀疏分类方法相比,取得了更好的分类性能,在AR、FERET、FRGC和LFW人脸数据库上的实验结果显示,当每类仅有一个训练样本时,EPCNN-SRC算法的识别率分别达到96.92%、96.15%、86.94%和42.44%,均高于传统的表示分类方法,充分验证了本文算法的有效性。同时,本文方法不仅提升了对测试样本稀疏表示的鲁棒性,而且在保证识别率的基础上,有效降低了算法的时间复杂度,在FERET数据库上的运行时间为4.92 s,均低于一些传统方法的运行时间。结论 基于卷积神经网络和PCA约束优化模型的稀疏表示分类方法,将深度学习特征与PCA方法相结合,不仅具有较好的识别准确度,而且对稀疏分类也具有很好的鲁棒性,尤其在小样本问题上优势显著。     

Extended sparse representation-based classification method for face recognition

In sparse representation algorithms, a test sample can be sufficiently represented by exploiting only the training samples from the same class. However, due to variations of facial expressions, illuminations and poses, the other classes also have different degrees of influence on the linear representation of the test sample. Therefore, in order to represent a test sample more accurately, we propose a new sparse representation-based classification method which can strengthen the discriminative property of different classes and obtain a better representation coefficient vector. In our method, we introduce a weighted matrix, which can make small deviations correspond to higher weights and large deviations correspond to lower weights. Meanwhile, we improve the constraint term of representation coefficients, which can enhance the distinctiveness of different classes and make a better positive contribution to classification. In addition, motivated by the work of ProCRC algorithm, we take into account the deviation between the linear combination of all training samples and of each class. Thereby, the discriminative representation of the test sample is further guaranteed. Experimental results on the ORL, FERET, Extended-YaleB and AR databases show that the proposed method has better classification performance than other methods.     

基于鉴别性低秩表示的2阶段人脸识别算法

针对图像训练样本中存在噪声等情况,提出一种基于鉴别性低秩表示的2阶段人脸识别算法。该算法第1阶段是对所有训练样本进行低秩处理,筛选出M类与测试样本最相近的样本用于粗分类;第2阶段使用第1阶段筛选出来的样本做鉴别性低秩表示处理,并使用稀疏线性表示进行精细分类,决定测试样本最适合的类标签。本算法结合了低秩算法与稀疏算法的优点,在标准人脸库上的实验表明本算法表现优越。     

基于类别相关近邻子空间的最大似然稀疏表示鲁棒图像识别算法

为了构建一个快速鲁棒的图像识别算法, 提出基于类别相关近邻子空间的最大似然稀疏表示图像识别算法. 考虑到每个测试样本的不同分布特性及训练样本选择的类别代表性原则, 不再将所有训练样本作为稀疏表示的字典, 而是基于距离相近准则选择合适子空间, 从每个类别中选取自适应数量的局部近邻构成新的字典, 在减少训练样本的同时保留了稀疏表示原有的子空间结构. 然后基于最大似然稀疏表示识别方法, 将稀疏表示的保真度表示为余项的最大似然函数, 并将识别问题转化为加权的稀疏优化问题. 在公用人脸与数字识别数据库上的实验证明该算法的合理性, 提高识别速度的同时保证了识别精度和算法的鲁棒性, 特别是对于遮挡与干扰图像具有较好的适应性.     

基于概率分析的稀疏表示算法及在布料印染检测中的应用

为解决布料印染过程中,由于布料的褶皱或机器的故障而导致走布出现跑偏现象,本文提出了基于概率分析的稀疏表示分类算法(P-SRC),将布料的检测问题转换为稀疏表示的图像分类问题;同时提出了自适应纹理窗口选择算法和自适应样本个数计算方法。先把初始无偏转的图像,通过旋转产生新的图像,再利用所有图像作为训练样本构造过完备字典,对采集到的测试图像,按照本文提出的算法进行稀疏表示并分类识别。根据测试样本所属的类可判断染布机在走布过程中布料是否有偏转以及偏转的角度。实验表明,该算法提高了图像的识别率。     

A simple and fast representation-based face recognition method

In this paper, we propose a very simple and fast face recognition method and present its potential rationale. This method first selects only the nearest training sample, of the test sample, from every class and then expresses the test sample as a linear combination of all the selected training samples. Using the expression result, the proposed method can classify the testing sample with a high accuracy. The proposed method can classify more accurately than the nearest neighbor classification method (NNCM). The face recognition experiments show that the classification accuracy obtained using our method is usually 2–10% greater than that obtained using NNCM. Moreover, though the proposed method exploits only one training sample per class to perform classification, it might obtain a better performance than the nearest feature space method proposed in Chien and Wu (IEEE Trans Pattern Anal Machine Intell 24:1644–1649, 2002), which depends on all the training samples to classify the test sample. Our analysis shows that the proposed method achieves this by modifying the neighbor relationships between the test sample and training samples, determined by the Euclidean metric.     

基于自编码器和稀疏表示的单样本人脸识别

单样本人脸识别因其在现实生活中的广泛应用而成为人脸识别领域的热门话题。单张训练样本条件下训练样本的缺少和复杂的类内人脸表情、光照、遮挡变化给单样本人脸识别研究带来困难。传统的基于稀疏表示的人脸识别方法需要大量的训练样本构成过完备的字典,因而在单样本条件下识别效果明显下滑。针对这一问题,提出一种基于有监督自编码器的带变化人脸样本生成方法,在保留身份信息的同时自动生成带变化的人脸图像用于单样本条件下的字典扩充,一定程度上缓解了单样本条件下的欠采样问题,弥补了训练集和测试集间的人脸变化信息差异,使得传统的稀疏表示方法能够适用于单样本人脸识别问题。在公共数据库上的实验结果不仅证明了该方法的有效性,而且对测试集中不同的人脸变化也展现出了较强的鲁棒性。     

改进的局部稀疏表示分类算法及其在人脸识别中的应用

近年来,稀疏表示分类(Sparse Representation Based Classification,SRC)方法在人脸识别中受到越来越多的关注。原始SRC方法使用所有的训练样本组成字典矩阵,当训练样本比较多时,稀疏系数的求解会变得非常耗时。为了解决这一问题,提出一种新的局部稀疏表示分类(Local SRC,LSRC)方法。该方法针对每个测试样本,根据测试样本和训练样本稀疏系数之间的相似性来选择部分训练样本,由这些训练样本组成字典,然后在这个字典上对测试样本进行稀疏分解。该方法性能相比于原始LSRC方法更稳定。在ORL、Yale和AR人脸库上的实验结果表明,该方法的效果优于SRC和LSRC。     

Heteroscedastic Sparse Representation Based Classification for Face Recognition

Sparse representation based classification (SRC) have received a great deal of attention in recent years. The main idea of SRC is to represent a given test sample as a sparse linear combina-tion of all training samples, then classifies the test sample by evaluating which class leads to the minimum residual. Although SRC has achieved good performance, especially in dealing with face occlusion and corruption, it must need a big occlusion dictionary which makes computation very expensive. In this paper, a novel method, called heteroscedastic sparse representation based classification (HSRC), is proposed to address this problem. In the presence of noises, the SRC model exists heteroscedasticity, which makes residual estimation inefficient. Therefore, heteroscedastic correction must be carried out for homoscedasticity by weighting various residuals with heteroscedastic estimation. As for heteroscedasticity, this paper establishes generalized Gaussian model through which to estimate. The proposed HSRC method is applied to face recognition (on the AR and Extended Yale B face databases). The experimental results show that HSRC has significantly less complexity than SRC, while it is more robust.     

基于核的两阶段稀疏表示的人脸识别研究

为了提高人脸识别的分类正确率,提出了一种基于核的两阶段稀疏表示(KBTPSR)的人脸识别方法.该方法首先利用一个非线性函数将原始数据空间映射到特征空间;然后,在该特征空间中将待测样本表示为所有训练样本的一个线性组合,接下来根据每个训练样本的表示贡献选出待测样本的M个最近邻;最后,将待测样本表示为上述M个最近邻的一个线性组合并且利用每一类训练样本对待测样本的表示贡献来完成分类.大量的实验结果表明,该方法可以获得很好的识别效果.     

基于稀疏表示的QR码识别

针对QR码图像受污染、破损、遮挡时识别软件无法识别的问题,提出一种基于稀疏表示的QR码识别方法。以40类QR码图像作为研究对象,每类13幅,其中每类随机选取3幅共120幅作为训练样本,余下400幅作为测试样本。所有训练样本组成稀疏表示字典,测试样本为训练样本的稀疏线性组合,表示系数是稀疏的,对每一个测试样本,计算其在字典上的投影,具有最小残差值的类别,即为分类所属类别。最后将提出的方法与QR码识读软件PsQREdit的识别结果做了对比和分析。实验结果表明：提出的方法对于部分受污染、破损、遮挡的图像仍能正确识别,具有很好的鲁棒性,为QR码的识别提供了一种新的有效方案。     

Kernel sparse representation based classification

Sparse representation has attracted great attention in the past few years. Sparse representation based classification (SRC) algorithm was developed and successfully used for classification. In this paper, a kernel sparse representation based classification (KSRC) algorithm is proposed. Samples are mapped into a high dimensional feature space first and then SRC is performed in this new feature space by utilizing kernel trick. Since samples in the high dimensional feature space are unknown, we cannot perform KSRC directly. In order to overcome this difficulty, we give the method to solve the problem of sparse representation in the high dimensional feature space. If an appropriate kernel is selected, in the high dimensional feature space, a test sample is probably represented as the linear combination of training samples of the same class more accurately. Therefore, KSRC has more powerful classification ability than SRC. Experiments of face recognition, palmprint recognition and finger-knuckle-print recognition demonstrate the effectiveness of KSRC.