Local Preserving Graphs Using Intra-Class Competitive Representation for Dimensionality Reduction of Hyperspectral Image

As a key technique in hyperspectral image pre-processing,dimensionality reduction has received a lot of attention.However,most of the graph-based dimensionality reduction methods only consider a single structure in the data and ignore the interfusion of multiple structures.In this paper,we propose two methods for combining intra-class competition for locally preserved graphs by constructing a new dictionary containing neighbourhood information.These two methods explore local information into the collaborative graph through competing constraints,thus effectively improving the overcrowded distribution of intra-class coefficients in the collaborative graph and enhancing the discriminative power of the algorithm.By classifying four benchmark hyperspectral data,the proposed methods are proved to be superior to several advanced algorithms,even under small-sample-size conditions.

2DPCA versus PCA for face recognition

Dimensionality reduction methods play an important role in face recognition. Principal component analysis(PCA) and two-dimensional principal component analysis(2DPCA) are two kinds of important methods in this field. Recent research seems like that 2DPCA method is superior to PCA method. To prove if this conclusion is always true, a comprehensive comparison study between PCA and 2DPCA methods was carried out. A novel concept, called column-image difference(CID), was proposed to analyze the difference between PCA and 2DPCA methods in theory. It is found that there exist some restrictive conditions when2 DPCA outperforms PCA. After theoretical analysis, the experiments were conducted on four famous face image databases. The experiment results confirm the validity of theoretical claim.

Research on will-dimension SIFT algorithms for multi-attitude face recognition

The results of face recognition are often inaccurate due to factors such as illumination,noise intensity,and affine/projection transformation.In response to these problems,the scale invariant feature transformation(SIFT) is proposed,but its computational complexity and complication seriously affect the efficiency of the algorithm.In order to solve this problem,SIFT algorithm is proposed based on principal component analysis(PCA) dimensionality reduction.The algorithm first uses PCA algorithm,which has the function of screening feature points,to filter the feature points extracted in advance by the SIFT algorithm;then the high-dimensional data is projected into the low-dimensional space to remove the redundant feature points,thereby changing the way of generating feature descriptors and finally achieving the effect of dimensionality reduction.In this paper,through experiments on the public ORL face database,the dimension of SIFT is reduced to 20 dimensions,which improves the efficiency of face extraction;the comparison of several experimental results is completed and analyzed to verify the superiority of the improved algorithm.

Research on Face Recognition Algorithm Based on Robust 2DPCA

As a new dimension reduction method, the two-dimensional principal component (2DPCA) can be well applied in face recognition, but it is susceptible to outliers. Therefore, this paper proposes a new 2DPCA algorithm based on angel-2DPCA. To reduce the reconstruction error and maximize the variance simultaneously, we choose F norm as the measure and propose the Fp-2DPCA algorithm. Considering that the image has two dimensions, we offer the Fp-2DPCA algorithm based on bilateral. Experiments show that, compared with other algorithms, the Fp-2DPCA algorithm has a better dimensionality reduction effect and better robustness to outliers.

Dimensionality reduction with adaptive graph

Graph-based dimensionality reduction （DR） methods have been applied successfully in many practical problems, such as face recognition, where graphs play a crucial role in modeling the data distribution or structure. However, the ideal graph is, in practice, difficult to discover. Usually, one needs to construct graph empirically according to various motivations, priors, or assumptions; this is inde- pendent of the subsequent DR mapping calculation. Different from the previous works, in this paper, we attempt to learn a graph closely linked with the DR process, and propose an al- gorithm called dimensionality reduction with adaptive graph （DRAG）, whose idea is to, during seeking projection matrix, simultaneously learn a graph in the neighborhood of a pre- specified one. Moreover, the pre-specified graph is treated as a noisy observation of the ideal one, and the square Frobenius divergence is used to measure their difference in the objective function. As a result, we achieve an elegant graph update for- mula which naturally fuses the original and transformed data information. In particular, the optimal graph is shown to be a weighted sum of the pre-defined graph in the original space and a new graph depending on transformed space. Empirical results on several face datasets demonstrate the effectiveness of the proposed algorithm.

Robust Face Recognition Against Expressions and Partial Occlusions

Facial features under variant-expressions and partial occlusions could have degrading effect on overall face recognition performance. As a solution, we suggest that the contribution of these features on final classification should be determined. In order to represent facial features＇ contribution according to their variations, we propose a feature selection process that describes facial features as local independent component analysis （ICA） features. These local features are acquired using locally lateral subspace （LLS） strategy. Then, through linear discriminant analysis （LDA） we investigate the intraclass and interclass representation of each local ICA feature and express each feature＇s contribution via a weighting process. Using these weights, we define the contribution of each feature at local classifier level. In order to recognize faces under single sample constraint, we implement LLS strategy on locally linear embedding （LLE） along with the proposed feature selection. Additionally, we highlight the efficiency of the implementation of LLS strategy. The overall accuracy achieved by our approach on datasets with different facial expressions and partial occlusions such as AR, JAFFE, FERET and CK% is 90.70%. We present together in this paper survey results on face recognition performance and physiological feature selection performed by human subjects.

Nearest-neighbor classifier motivated marginal discriminant projections for face recognition

Marginal Fisher analysis （MFA） is a repre- sentative margin-based learning algorithm for face recognition. A major problem in MFA is how to select appropriate parameters, k1 and k2, to construct the respective intrinsic and penalty graphs. In this paper, we propose a novel method called nearest-neighbor （NN） classifier motivated marginal discriminant projections （NN-MDP）. Motivated by the NN classifier, NN-MDP seeks a few projection vectors to prevent data samples from being wrongly categorized. Like MFA, NN-MDP can characterize the compactness and separability of samples simultaneously. Moreover, in contrast to MFA, NN-MDP can actively construct the intrinsic graph and penalty graph without unknown parameters. Experimental results on the 0RL, Yale, and FERET face databases show that NN-MDP not only avoids the intractability, and high expense of neighborhood parameter selection, but is also more applicable to face recognition with NN classifier than other methods.

Face Recognition on Partial and Holistic LBP Features

An algorithm for face description and recognition based on multi-resolution with multi-scale local binary pattern （multi-LBP） features is proposed. The facial image pyramid is constructed and each facial image is divided into various regions from which partial and holistic local binary patter （LBP） histograms are extracted. All LBP features of each image are concatenated to a single LBP eigenvector with different resolutions. The dimensionaUty of LBP features is then reduced by a local margin alignment （LMA） algorithm based on manifold, which can preserve the between-class variance. Support vector machine （SVM） is applied to classify facial images. Extensive experiments on ORL and CMU face databases clearly show the superiority of the proposed scheme over some existed algorithms, especially on the robustness of the method against different facial expressions and postures of the subjects.

Orthogonal isometric projection for face recognition

Isometric projection （IsoProjection） is a linear dimensionality reduction method, which explicitly takes into account the manifold structure embedded in the data. However, IsoProjection is non-orthogonal, which makes it extremely sensitive to the dimensions of reduced space and difficult to estimate the intrinsic dimensionality. The non-ortbogonality also distorts the metric structure embedded in the data. This paper proposes a new method called orthogonal isometric projection （O-IsoProjection）, which shares the same linear character as IsoProjection and overcomes the metric distortion problem of IsoProjection. Similar to IsoProjection, O-lsoProjection firstly constructs an adjacency graph which can reflect the manifold structure embedded in the data and the class relationship between the sample points of face space, and then obtains the projections by preserving such a graph structure. Different from IsoProjection, O-IsoProjection requires the basis vectors to be orthogonal, and the orthogonal basis vectors can be calculated by iterative way. Experimental results on ORL and Yale databases show that O-lsoProjection has better recognition rate for face recognition than Eigenface, Fisherface and IsoProjection.

优化的近邻保持嵌入算法在人脸识别中的应用

为验证优化的近邻保持算法(ONPE)在人脸识别中的应用价值,在NPE算法基础之上,ONPE对数据类内和数据类间的信息分别进行了优化,以使在低维重建时同一数据类间相互靠拢,不同数据类间相互分离。将ONPE算法应用于手工流形和Fery face人脸库进行实验。结果表明:在样本点不足且不连续的情况下,ONPE可以对手工流形有很好的降维效果,并且对人脸表情数据也有很好的识别分类效果。因此,优化的近邻保持嵌入算法具有较强的实用性和有效性。

基于结构化深度聚类网络的人脸表情识别研究

针对如今常用的卷积神经网络对人脸表情图片的特征提取不足、关键区域的特征无法精确提取等问题,文章利用不同表情时人脸关键点的变化,并将深度学习方法与聚类方法相结合运用于人脸表情识别中,提出一种基于结构化深度聚类网络(SDCN)的人脸表情识别算法.该网络由GCN图卷积神经网络、K-最近邻(KNN)图构建网络、编码器网络构成.为更好地捕捉到人脸关键点之间的关系和表情信息,利用GCN网络对人脸表情图像中的关键点进行特征提取.该网络输入数据为图结构数据,将人脸关键点数据输入对应的KNN图构建网络以得到人脸关键点的图结构数据.该网络在Fer2013、CK+与JAFFE三个人脸表情数据库上进行实验,获得了较为不错的识别率,在一定程度上证实了算法的有效性.

基于机器视觉的局部遮挡人脸图像识别仿真

与无遮挡条件下的人脸识别不同,在局部遮挡下目标识别中需要考虑有效部位与遮挡部位的区别,准确提取目标区域,为此提出基于机器视觉的局部遮挡人脸图像识别方法。通过成对约束的半监督降维算法对人脸图像降维处理,获取图像中的显著特征,减少图像中的噪声。经过降维处理后,通过机器视觉技术提取局部遮挡下人脸图像的目标区域,确定目标区域的坐标位置。采用Criminisi修复算法获取未修复的人脸图像块数量,搜索最佳匹配块,同时对目标区域填充处理,完成人脸图像修复即可获取完整的人脸图像,最终实现人脸识别。实验结果表明,所提方法可以准确识别不同遮挡率下的人脸,同时可以减少识别时间,降低了遮挡问题对人脸识别效果的影响。

基于边界判别投影的数据降维

为了提取具有较好判别性能的低维特征,提出了一种新的有监督的线性降维算法——边界判别投影,即,最小化同类样本间的最大距离,最大化异类样本间的最小距离,同时保持数据流形的几何形状.与经典的基于边界定义的算法相比,边界判别投影可以较好地保持数据流形的几何结构和判别结构等全局特性,可避免小样本问题,具有较低的计算复杂度,可应用于超高维的大数据降维.人脸数据集上的实验结果表明,边界判别分析是一种有效的降维算法,可应用于大数据上的特征提取.

张量局部Fisher判别分析的人脸识别

子空间特征提取是人脸识别中的关键技术之一,结合局部Fisher判别分析技术和张量子空间分析技术的优点,本文提出了一种新的张量局部Fisher判别分析(Tensor local Fisher discriminant analysis,TLFDA)子空间降维技术.首先,通过对局部Fisher判别技术进行分析,调整了其类间散度目标泛函,使算法的识别性能更高且时间复杂度更低;其次,引入张量型降维技术对输入数据进行双边投影变换而非单边投影,获得了更高的数据压缩率;最后,采用迭代更新的方法计算最优的变换矩阵.通过ORL和PIE两个人脸库验证了所提算法的有效性.

基于线性降维技术和BP神经网络的热红外人脸图像识别

结合线性降维技术与BP神经网络对热红外人脸图像进行了识别研究.首先利用主成分分析和线性判别分析对热红外人脸图像进行图像降维及特征提取,然后将提取出的热红外人脸图像特征向量用于BP神经网络的训练,得到一个鲁棒性和容错性较强的分类器,用这个分类器对热红外人脸图像进行分类识别.实验结果表明,由于所提方法在提取便于分类的模式特征基础上,采用神经网络作为分类器代替特征向量间的欧氏距离判别,获得了较高的热红外人脸图像识别率.

依概率分类的保持投影及其在人脸识别中的应用

为了提高低维空间对原始高维样本的表示能力,该文提出了依概率分类的保持投影算法(PCPP)。PCPP考虑了样本类别信息,并重新定义类内样本间的相似性,包含样本的邻域信息,而且在K近邻选择下,还能反映样本被正确归类的概率。样本经投影后,在低维特征空间内,被正确归类且概率较大的类内样本间的邻域关系得到了保持。在Yale、FERET及AR人脸库上的人脸识别实验表明,PCPP较其他算法取得了更好的识别性能。

融合LLE和ISOMAP的非线性降维方法

局部线性嵌入(LLE)和等距映射(ISOMAP)在降维过程中都只单一地保留数据集的某一种特性结构,从而使降维后的数据集往往存在顾此失彼的情况。针对这种情况,借助流形学习的核框架,提出融合LLE和ISOMAP的非线性降维方法。新的融合方法使降维后的数据集既保持着数据点间的局部邻域关系,也保持着数据点间的全局距离关系。在仿真数据集和实际数据集上的实验结果证实了该方法的优越性。

融合半监督降维与稀疏表示的人脸识别方法

由于人脸图像数据的维数都较高,将稀疏表示分类用于人脸识别时计算量很大,为了提高人脸识别系统的效率,提出了一种融合半监督降维和稀疏表示的人脸识别方法。首先利用半监督降维算法对图像进行降维处理,在较低的维数空间快速取得较高的识别率,然后利用稀疏表示分类进行人脸识别,取得比传统的最近邻分类器更高的识别率,最后在ORL人脸库上进行实验验证。结果表明,利用该融合算法可快速有效地提高人脸图像的识别效果。

近邻边界Fisher判别分析

将数据集进行合理的维数约简对于一些机器学习算法效率的提高起着至关重要的影响。该文提出了一种利用数据点邻域信息的线性监督降维算法:近邻边界Fisher判别分析(Neighborhood Margin Fisher Discriminant Analysis,NMFDA)。NMFDA尝试将每一数据点邻域内最远的同类数据点和最近的异类数据点之间的边界在投影子空间内尽可能地扩大,从而提高基于距离的识别算法的准确率。同时为了解决非线性降维问题,提出了Kernel NMFDA,通过在几个标准人脸数据库上与其它降维算法的对比识别实验,验证了提出算法的有效性。

基于马氏距离的局部边界Fisher分析降维算法

针对人脸识别应用中的高维数据图像以及欧氏距离不能准确体现样本间的相似度的问题,提出了一种基于马氏距离的局部边界Fisher分析(MLMFA)降维算法。该算法从现有的样本中学习得到一个马氏度量,然后在近邻选择以及新样本降维过程中用马氏距离作为相似性度量。同时,通过马氏度量构造出类内"相似"图和类间"代价"图来描述数据集的类内紧凑性和类间分离性。MLMFA很好地保持了数据集的局部结构。用YALE和FERET人脸库进行实验,MLMFA的最大识别率比传统基于欧氏距离算法的最大识别率平均分别提高了1.03%和6%。实验结果表明,算法MLMFA具有很好的分类和识别性能。