基于光照归一化分块完备LBP特征的人脸识别

针对复杂光照条件下的人脸识别,提出了一种基于光照归一化分块完备局部二值模式（B-CLBP）特征的人脸识别算法。该方法对人脸图像进行光照归一化预处理,对处理后的人脸图像进行B-CLBP特征提取,融合成B-CLBP直方图,根据最近邻准则进行分类识别。在Extended Yale B人脸库上的实验结果表明,所提算法可以有效提高复杂光照条件下的人脸识别率。     

基于随机投影与加权稀疏表示残差的光照鲁棒人脸识别方法

针对人脸识别中的光照变化问题,利用随机投影对传统稀疏表示分类器进行改进,提出一种基于随机投影与加权稀疏表示残差的光照鲁棒人脸识别方法。通过对人脸图像进行光照规范化处理,尽量消除人脸图像上的恶劣光照,取得经光照校正的人脸样本后进行多次随机空间投影,进一步丰富样本的光照不变特征,以减小光照变化对人脸识别带来的影响。在此基础上,对利用单一残差分类的传统稀疏表示分类方法进行改进,样本经过多次随机投影和稀疏表示会产生多个样本特征和重构残差,利用样本特征的能量来确定各个重构残差的融合权值,最终得到一种稳定性和可靠性更强的加权残差。在 Yale B 和 CMU PIE 两个光照变化较大的人脸库上的实验结果表明,改进的方法具有较强的光照鲁棒性。与传统稀疏表示方法相比,本文提出的方法在Yale B人脸库上两组实验的平均识别率分别提高了25.76%和46.39%,在CMU PIE上的平均识别率提高了10%左右。     

基于核的多元区别分析算法的特征抽取及其在人脸识别中的应用

提出了一种基于核技术的求多元区别分析最佳解的K1PMDA算法，并把这一算法应用于人脸识别中。对线性人脸识别中存在两个突出问题：1、在光照、表情、姿态变化较大时，人脸图像分类是复杂的、非线性的；2、小样本问题，即当训练样本数量小于样本特征空间维数时，导致类内散布矩阵奇异。对于前一个问题，可以采用核技术提取人脸图像样本的非线性特征，对于后一个问题，采用加入一个扰动参数的扰动算法。通过对ORL，Yale Group B以及UMIST三个人脸库的实验表明，该算法是可行的、高效的。     

Illumination invariant face recognition

The appearance of a face will vary drastically when the illumination changes. Variations in lighting conditions make face recognition an even more challenging and difficult task. In this paper, we propose a novel approach to handle the illumination problem. Our method can restore a face image captured under arbitrary lighting conditions to one with frontal illumination by using a ratio-image between the face image and a reference face image, both of which are blurred by a Gaussian filter. An iterative algorithm is then used to update the reference image, which is reconstructed from the restored image by means of principal component analysis (PCA), in order to obtain a visually better restored image. Image processing techniques are also used to improve the quality of the restored image. To evaluate the performance of our algorithm, restored images with frontal illumination are used for face recognition by means of PCA. Experimental results demonstrate that face recognition using our method can achieve a higher recognition rate based on the Yale B database and the Yale database. Our algorithm has several advantages over other previous algorithms: (1) it does not need to estimate the face surface normals and the light source directions, (2) it does not need many images captured under different lighting conditions for each person, nor a set of bootstrap images that includes many images with different illuminations, and (3) it does not need to detect accurate positions of some facial feature points or to warp the image for alignment, etc.     

改进的单尺度Retinex和LBP结合的人脸识别

为了提高复杂光照条件下人脸识别准确率,提出一种基于改进单尺度Retinex并结合局部二值模式（LBP）的人脸识别算法。首先,利用双边滤波代替Retinex的高斯滤波处理人脸图像,同时使用高斯-拉普拉斯（LoG）及归一化处理提取人脸图像的边缘细节特征,采用标准差的加权方法将两幅处理后的图像进行特征融合,然后使用LBP对融合后的图像进行特征提取,最后通过稀疏表示（SRC）算法对数据样本进行判别归类。在AR和Yale B+人脸库上的实验测试表明,提高了复杂光照下人脸识别的光照鲁棒性,在训练样本较少、光照复杂环境下能取得较好的识别效果。     

基于球面谐波基图像的任意光照下的人脸识别

提出了一种基于球面谐波基图像的光照补偿算法,用以在任意光照条件下进行人脸识别.算法分两步进行：光照估计和光照补偿.基于人脸形状大致相同和每个人脸的反射率基本相等的假设,首先估计了输入人脸图像光照的9个低频谐波系数.根据光照估计的结果,提出了两种光照补偿方法：纹理图像和差图像.纹理图像为输入图像与其光照辐照图之商,与输入图像的光照条件无关.差图像为输入图像与平均人脸在相同光照下的图像之差,通过减去平均人脸在相同光照下的图像,减弱了光照的影响.在CMU-PIE人脸库和Yale B人脸库上的实验表明,通过光照补偿,不同光照下人脸图像识别率有了很大提高.     

一种复杂光照下的人脸识别算法

为提高光照变化下的人脸识别率,提出了一种基于局部对比增强（LCE）和局部相位量化（LPQ）的人脸识别方法。采用面部对称的思想结合LCE算法对受不均匀光照的人脸图像进行光照补偿;利用LPQ算子对增强后的图片进行标记,并用分块离散余弦变换（DCT）进行降维;分块计算LPQ直方图序列作为人脸图像的特征描述向量,送入最近邻分类器进行分类识别。通过Yale B和CAS_PEAL数据库上的实验,证实了所提方法的有效性。     

基于FABEMD的变化光照下人脸识别方法

在光照变化的环境下,人脸识别因受到光照强度和方向的非线性干扰而变得困难重重。在人脸局部区域,光照的变化比较缓慢,而皮肤对光照的反射率特征变化比较快,可以认为光照变化是低频信号,而人脸本质特征是高频信号。FABEMD是一种快速自适应的BEMD（Bidimensional Empirical Mode Decomposition,二维经验模式分解）方法,它能够将图像分解为不同尺度的高频图像和低频图像,高频图像代表了人脸皮肤细节纹理特征,而低频图像则代表了轮廓特征。但是并不能定量判别什么样的高频信号以及多少高频信号能够用来消除光照影响,所以提出了两种衡量高频细节信息量的方法,将这些信息量的相对值来推算融合不同尺度的高频信号权重系数。基于Yale B人脸数据库的实验数据证明了所提方法能够取得很好的识别效果。     

自适应特征提取的光照鲁棒性人脸识别

针对光照对人脸特征提取的影响,提出了一种基于多尺度Curvelet变换的自适应局部熵的光照鲁棒性人脸特征提取方法。采用特殊局部对比增强算法对光照不均衡图像进行光照补偿,同时使图像局部特征显著;通过对增强后的图像进行Curvelet多尺度分解,得到的分解系数进行分块求熵从而构成候选特征向量;通过特征鉴别能力分析和评估,对候选特征值进行最优选择。在ORL,Yale,YaleB,AR四个人脸数据库中的实验结果表明,该方法与传统的PCA,LDA方法相比,避免小样本和特征分解问题,同时具有环境适应性和抗光照影响的特点。     

Principal Angles Separate Subject Illumination Spaces in YDB and CMU-PIE

The theory of illumination subspaces is well developed and has been tested extensively on the Yale Face Database B (YDB) and CMU-PIE (PIE) data sets. This paper shows that if face recognition under varying illumination is cast as a problem of matching sets of images to sets of images, then the minimal principal angle between subspaces is sufficient to perfectly separate matching pairs of image sets from nonmatching pairs of image sets sampled from YDB and PIE. This is true even for subspaces estimated from as few as six images and when one of the subspaces is estimated from as few as three images if the second subspace is estimated from a larger set (10 or more). This suggests that variation under illumination may be thought of as useful discriminating information rather than unwanted noise.     

基于小波变换和去噪模型的光照不变人脸识别

针对正面光照人脸识别的难点,提出了一种应用小波变换和去噪模型的光照不变人脸识别算法。利用对图像的高频小波系数进行处理并运用去噪模型,提取光照人脸图像中的光照不变量,同时增强图像边缘特征,这有利于提取的光照不变量保持更多的人脸识别信息。在Yale B和CMU PIE人脸库上的实验结果表明,所提算法可以显著提高光照人脸图像的识别率。     

基于KIOFD算法的特征抽取及其在人脸识别中的应用

提出了一种基于核技术的融合了反转Fisher鉴别准则和正交化技术的KIOFD（Kernel Inverse Orthogonalized Fisher Discriminant）算法,并把这一算法应用于人脸识别中。线性人脸识别中存在两个突出问题:（1）在光照、表情、姿态变化较大时,人脸图像分类是复杂的、非线性的;（2）小样本问题,即当训练样本数量小于样本特征空间维数时,导致类内散布矩阵奇异。对于第1个问题,可以采用核技术提取人脸图像样本的非线性特征,对于第2个问题,采用了反转Fisher鉴别准则和正交化结合的算法。通过对ORL、Yale Group B以及UMIST3个人脸库的实验表明,提出的算法是可行的、高效的。     

Illumination robust single sample face recognition using multi-directional orthogonal gradient phase faces

Due to the limitation of the storage space in the real-world face recognition application systems, only one sample image per person is often stored in the system, which is the so-called single sample problem. Moreover, real-world illumination has impact on recognition performance. This paper presents an illumination robust single sample face recognition approach, which utilizes multi-directional orthogonal gradient phase faces to solve the above limitations. In the proposed approach, an illumination insensitive orthogonal gradient phase face is obtained by using two vertical directional gradient values of the original image. Multi-directional orthogonal gradient phase faces can be used to extend samples for single sample face recognition. Simulated experiments and comparisons on a subset of Yale B database, Yale database, a subset of PIE database and VALID face database show that the proposed approach is not only an outstanding method for single sample face recognition under illumination but also more effective when addressing illumination, expression, decoration, etc.     

基于LBP和栈式自动编码器的人脸识别算法研究

LBP算法对光照敏感且能有效地提取图像的纹理结构特征。提出一种基于局部二值模式（Local Binary Pattern,LBP）和栈式自动编码器（Stacked Autoencoders,SAE）的人脸识别算法。用统一模式LBP算子提取分块后的人脸图像的直方图,按顺序连接形成整幅图像的LBP特征,并将其作为栈式自动编码器的输入,完成进一步的特征提取,实现人脸图像的识别与分类。在Extended Yale B等数据库上的实验结果表明,该算法与传统的人脸识别算法和标准的栈式自动编码器相比,对光照变化有更强的鲁棒性,具有更好的识别效果。     

Kernel machine-based one-parameter regularized fisher discriminant method for face recognition.

This paper addresses two problems in linear discriminant analysis (LDA) of face recognition. The first one is the problem of recognition of human faces under pose and illumination variations. It is well known that the distribution of face images with different pose, illumination, and face expression is complex and nonlinear. The traditional linear methods, such as LDA, will not give a satisfactory performance. The second problem is the small sample size (S3) problem. This problem occurs when the number of training samples is smaller than the dimensionality of feature vector. In turn, the within-class scatter matrix will become singular. To overcome these limitations, this paper proposes a new kernel machine-based one-parameter regularized Fisher discriminant (K1PRFD) technique. K1PRFD is developed based on our previously developed one-parameter regularized discriminant analysis method and the well-known kernel approach. Therefore, K1PRFD consists of two parameters, namely the regularization parameter and kernel parameter. This paper further proposes a new method to determine the optimal kernel parameter in RBF kernel and regularized parameter in within-class scatter matrix simultaneously based on the conjugate gradient method. Three databases, namely FERET, Yale Group B, and CMU PIE, are selected for evaluation. The results are encouraging. Comparing with the existing LDA-based methods, the proposed method gives superior results.     

改进型Gabor自商图算法及其在人脸识别中的应用

光照变化是影响人脸识别系统性能的关键问题之一,针对该问题提出了一种改进的基于Gabor特征的自商图算法。对人脸图像采用改进的加权Gabor滤波器进行平滑的Gabor特征提取,使用自商图像的方法求取图像的光照不变特征;对得到的自商图像用直方图截断等方法进行归一化;在Extended Yale B与CMU PIE人脸库上通过基于皮尔逊相关系数的最近邻方法进行实验。实验结果表明,与传统算法相比,该算法可以大幅度提高人脸识别率。     

A method of illumination compensation for human face image based on quotient image

Illumination variation is one of the critical factors affecting face recognition rate. A novel approach for human face illumination compensation is presented in this paper. It constructs the nine-dimension face illumination subspace based on quotient image. In addition, with the aim to improve algorithm efficiency, a half-face illumination image is proposed and the low-dimension training set of the face image under different illumination conditions are obtained by means of PCA and wavelet transform. After processing, two different illumination compensation strategies are given: one is adding light, and the other is removing light. Based on the illumination compensation strategy, we implement the typical illumination sample image synthesis and the standard illumination sample image synthesis on a PCA feature subspace and a wavelet transform subspace, respectively, and the illumination compensation of the gray images and the color images are further realized. Experimental results based on the Yale Face Database B, the Extended Yale Face Database B and the CAS-PEAL Face Database indicate that execution time after compensation is approximately half the time and face recognition rate is improved by 20% compared with that of the original images.     

基于Haar特性的改进HOG的人脸特征提取算法

现有的大多数特征提取算法在提取人脸特征时,容易受到光照等外界因素的影响,从而导致后期人脸识别率下降。而方向梯度直方图(Histogram of Oriented Gradient,HOG)具有较强的光照鲁棒性,能够很好地减少由光照带来的干扰,但传统HOG在计算梯度幅值和方向时只计算水平和垂直方向上4个像素点对中间像素的影响,当外界环境变化时不能保证稳定性,因此提出一种基于Haar特性的改进HOG的人脸特征提取算法。该算法在计算梯度幅值和方向时考虑水平、垂直以及对角线上8个像素点对中间像素的影响,由于增加计算量导致特征提取时间也随之增加,因此引入Haar,借助Haar型特征运算简单、快捷的特点设计4组Haar型特征编码模式,按照改进的HOG特征计算方式提取人脸特征。在有光照等外界因素影响的FERET人脸数据库和Yale B扩展的人脸测试库中进行实验,实验结果表明,与GFC,LBP和其他文献中的HOG算法相比,该算法对光照具有更好的鲁棒性,能够在光照变化的环境下提高人脸识别率。该算法在FERET探测集fb,fc,dup1和dup2上的识别率分别为95.1%,80.9%,70.1%和63.2%,在Yale B中的识别率为89.1%。     

Toward a practical face recognition system: robust alignment and illumination by sparse representation

Many classic and contemporary face recognition algorithms work well on public data sets, but degrade sharply when they are used in a real recognition system. This is mostly due to the difficulty of simultaneously handling variations in illumination, image misalignment, and occlusion in the test image. We consider a scenario where the training images are well controlled and test images are only loosely controlled. We propose a conceptually simple face recognition system that achieves a high degree of robustness and stability to illumination variation, image misalignment, and partial occlusion. The system uses tools from sparse representation to align a test face image to a set of frontal training images. The region of attraction of our alignment algorithm is computed empirically for public face data sets such as Multi-PIE. We demonstrate how to capture a set of training images with enough illumination variation that they span test images taken under uncontrolled illumination. In order to evaluate how our algorithms work under practical testing conditions, we have implemented a complete face recognition system, including a projector-based training acquisition system. Our system can efficiently and effectively recognize faces under a variety of realistic conditions, using only frontal images under the proposed illuminations as training.     

Robust face recognition using generalized neural reflectance model

A generalized neural reflectance (GNR) model for enhancing face recognition under variations in illumination and posture is presented in this paper. Our work is based on training a number of synthesis images of each face taken at single lighting direction with frontal/posture view. This way of synthesizing images can be used to build training cases for each face under different known illumination conditions from which face recognition can be significantly improved. However, reconstructing face shape may not easily be achieved and the human face images usually form by highly complex structure which suffers from strong specular and unknown reflective conditions. In this paper, these limitations are addressed by Cho and Chow (IEEE Trans Neural Netw 12(5):1204–1214, 2002). Face surfaces are recovered by this GNR model and face images in different poses are synthesized to create a database for training. Our training algorithm assigns to recognize the face identity by similarity measure on face features extracting first by the principle component analysis (PCA) method and then further processing by the Fisher’s discrimination analysis (FDA) to acquire lower dimensional patterns. Experimental results conducted on the Yale Face Database B show that lower error rates of classification and recognition are achieved under different variations in lighting and pose and the performance significantly outperforms the recognition without using the proposed GNR model.