人脸识别技术综述

首先对计算机人脸自动识别技术的研究背景及发展历程做了简单回顾,然后对人脸正面像的识别方法,按照识别特征的不同进行了分类综述,主要介绍了特征脸（Ｅｉｇｅｎｆａｃｅ）方法、基于小波特征的弹性匹配（Ｅｌａｓｔｉｃ Ｍａｔｃｈｉｎｇ）的方法、形状和灰度模型分离的可变形模型（Ｆｌｅｘｉｂｌ Ｍｏｄｅｌ）以及传统的部件建模等分析方法。通过对各种识别方法的分析与比较,总结了影响人脸识别技术实用化的几个因素,并提出了研究和开发成功的人脸识别技术所需要考虑的几个重要方面,进而展望了人脸识别技术今后的发展方向。     

Quantitative analysis of human facial beauty using geometric features

Perception of human facial beauty is an important aspect of human intelligence and has attracted interests of researchers from diverse fields such as psychology and computer science. Previous studies, however, have the following limitations. First, they did not well quantify the facial feature space. Second, they seldom consider the transformation occurring to faces or the physical sizes of faces. Third, most of them require intensive manual work, e.g. marking landmarks. To overcome these limitations, this paper maps faces onto a human face shape space, and then quantitatively analyses the effect of facial geometric features on human facial beauty by using a similarity transformation invariant shape distance measurement and advanced automatic image processing techniques. With the proposed methodology, we experiment on tens of thousands of female and male faces, revealing that human face shapes lie in a very compact region of the geometric feature space and that female and male average face shapes are very similar. Further, we demonstrate that a face can become more beautiful by making its geometric feature getting obviously closer to the average face shape, but if its distance to the average face shape is already relatively small, deforming it further toward the average face shape cannot effectively improve its attractiveness.     

Generating discriminating cartoon faces using interacting snakes

As a computational bridge between the high-level a priori knowledge of object shape and the low-level image data, active contours (or snakes) are useful models for the extraction of deformable objects. We propose an approach for manipulating multiple snakes iteratively, called interacting snakes, that minimizes the attraction energy functionals on both contours and enclosed regions of individual snakes and the repulsion energy functionals among multiple snakes that interact with each other. We implement the interacting snakes through explicit curve (parametric active contours) representation in the domain of face recognition. We represent human faces semantically via facial components such as eyes, mouth, face outline, and the hair outline. Each facial component is encoded by a closed (or open) snake that is drawn from a 3D generic face model. A collection of semantic facial components form a hypergraph, called semantic face graph, which employs interacting snakes to align the general facial topology onto the sensed face images. Experimental results show that a successful interaction among multiple snakes associated with facial components makes the semantic face graph a useful model for face representation, including cartoon faces and caricatures, and recognition.     

3D human face description: landmarks measures and geometrical features

Distance measures and geometrical features are widely used to describe faces. Generally, they are extracted punctually from landmarks, namely anthropometric reference points. The aims are various, such as face recognition, facial expression recognition, face detection, study of changes in facial morphology due to growth, or dysmorphologies. Most of the time, landmarks were extracted with the help of an algorithm or manually located on the faces. Then, measures are computed or geometrical features are extracted to perform the scope of the study. This paper is intended as a survey collecting and explaining all these features, in order to provide a structured user database of the potential parameters and their characteristics. Firstly, facial soft-tissue landmarks are defined and contextualized; then the various measures are introduced and some results are given; lastly, the most important measures are compared to identify the best one for face recognition applications.     

Face recognition using line edge map

The automatic recognition of human faces presents a significant challenge to the pattern recognition research community. Typically, human faces are very similar in structure with minor differences from person to person. They are actually within one class of "human face". Furthermore, lighting conditions change, while facial expressions and pose variations further complicate the face recognition task as one of the difficult problems in pattern analysis. This paper proposes a novel concept: namely, that faces can be recognized using a line edge map (LEM). The LEM, a compact face feature, is generated for face coding and recognition. A thorough investigation of the proposed concept is conducted which covers all aspects of human face recognition, i.e. face recognition under (1) controlled/ideal conditions and size variations, (2) varying lighting conditions, (3) varying facial expressions, and (4) varying pose. The system performance is also compared with the eigenface method, one of the best face recognition techniques, and with reported experimental results of other methods. A face pre-filtering technique is proposed to speed up the search process. It is a very encouraging to find that the proposed face recognition technique has performed better than the eigenface method in most of the comparison experiments. This research demonstrates that the LEM, together with the proposed generic line-segment Hausdorff distance measure, provides a new method for face coding and recognition     

Bilinear Models for 3-D Face and Facial Expression Recognition

In this paper, we explore bilinear models for jointly addressing 3-D face and facial expression recognition. An elastically deformable model algorithm that establishes correspondence among a set of faces is proposed first and then bilinear models that decouple the identity and facial expression factors are constructed. Fitting these models to unknown faces enables us to perform face recognition invariant to facial expressions and facial expression recognition with unknown identity. A quantitative evaluation of the proposed technique is conducted on the publicly available BU-3DFE face database in comparison with our previous work on face recognition and other state-of-the-art algorithms for facial expression recognition. Experimental results demonstrate an overall 90.5% facial expression recognition rate and an 86% rank-1 face recognition rate.      

Combining appearance and motion for face and gender recognition from videos

While many works consider moving faces only as collections of frames and apply still image-based methods, recent developments indicate that excellent results can be obtained using texture-based spatiotemporal representations for describing and analyzing faces in videos. Inspired by the psychophysical findings which state that facial movements can provide valuable information to face analysis, and also by our recent success in using LBP (local binary patterns) for combining appearance and motion for dynamic texture analysis, this paper investigates the combination of facial appearance (the shape of the face) and motion (the way a person is talking and moving his/her facial features) for face analysis in videos. We propose and study an approach for spatiotemporal face and gender recognition from videos using an extended set of volume LBP features and a boosting scheme. We experiment with several publicly available video face databases and consider different benchmark methods for comparison. Our extensive experimental analysis clearly assesses the promising performance of the LBP-based spatiotemporal representations for describing and analyzing faces in videos.     

人脸样貌独立判别的协作表情识别算法

为了降低样貌、姿态、眼镜以及表情定义不统一等因素对人脸表情识别的影响,提出一种人脸样貌独立判别的协作表情识别算法。首先,采用自动的人脸检测算法定位、对齐视频每帧的人脸区域,并从人脸视频序列中选择峰值表情的人脸;然后,采用峰值人脸与某个表情类内的所有人脸产生表情类内差异人脸信息,并通过计算峰值表情人脸与表情类内差异人脸的差异信息获得协作的表情表示;最终,采用基于稀疏的分类器与表情表示决定每个人脸表情的标签。采用欧美与亚洲人脸的数据库进行仿真实验,结果表明本算法获得了较好的表情识别准确率,对不同样貌、佩戴眼镜的人脸样本也具有较好的识别效果。     

一种基于多视点图象的可变姿态人脸识别系统

本文报告了一种多姿态人脸图象识别原型系统，它不同于现有系统和方法，该系统可工作在合作对象下允许姿态变化（存在图象平面内旋转和深度方向上旋转，限于双眼可见）的人脸图象识别。由于对成象条件有所放松，故可望应用于身份验证、保安和视频会议等领域。对姿态可变条件下的人脸特征检测、姿态估计、识别建模以及基于模板相关的匹配等技术进行了深人研究，分析了光照、姿态及分辨率变化等因素对识别的影响程度。实验结果表明，对于３０类人脸，每人１８幅图象大小的测试集，达到了１００％的识别率。     

Statistical shape modelling for expression-invariant face analysis and recognition

Paper introduces a 3-D shape representation scheme for automatic face analysis and identification, and demonstrates its invariance to facial expression. The core of this scheme lies on the combination of statistical shape modelling and non-rigid deformation matching. While the former matches 3-D faces with facial expression, the latter provides a low-dimensional feature vector that controls the deformation of model for matching the shape of new input, thereby enabling robust identification of 3-D faces. The proposed scheme is also able to handle the pose variation without large part of missing data. To assist the establishment of dense point correspondences, a modified free-form-deformation based on B-spline warping is applied with the help of extracted landmarks. The hybrid iterative closest point method is introduced for matching the models and new data. The feasibility and effectiveness of the proposed method was investigated using standard publicly available Gavab and BU-3DFE datasets, which contain faces with expression and pose changes. The performance of the system was compared with that of nine benchmark approaches. The experimental results demonstrate that the proposed scheme provides a competitive solution for face recognition.     

基于特征点表情变化的3维人脸识别

目的 为克服表情变化对3维人脸识别的影响,提出一种基于特征点提取局部区域特征的3维人脸识别方法。方法 首先,在深度图上应用2维图像的ASM(active shape model)算法粗略定位出人脸特征点,再根据Shape index特征在人脸点云上精确定位出特征点。其次,提取以鼻中为中心的一系列等测地轮廓线来表征人脸形状;然后,提取具有姿态不变性的Procrustean向量特征(距离和角度)作为识别特征;最后,对各条等测地轮廓线特征的分类结果进行了比较,并对分类结果进行决策级融合。结果 在FRGC V2.0人脸数据库分别进行特征点定位实验和识别实验,平均定位误差小于2.36 mm,Rank-1识别率为98.35%。结论 基于特征点的3维人脸识别方法,通过特征点在人脸近似刚性区域提取特征,有效避免了受表情影响较大的嘴部区域。实验证明该方法具有较高的识别精度,同时对姿态、表情变化具有一定的鲁棒性。     

Automatic interpretation and coding of face images using flexiblemodels

Face images are difficult to interpret because they are highly variable. Sources of variability include individual appearance, 3D pose, facial expression, and lighting. We describe a compact parametrized model of facial appearance which takes into account all these sources of variability. The model represents both shape and gray-level appearance, and is created by performing a statistical analysis over a training set of face images. A robust multiresolution search algorithm is used to fit the model to faces in new images. This allows the main facial features to be located, and a set of shape, and gray-level appearance parameters to be recovered. A good approximation to a given face can be reconstructed using less than 100 of these parameters. This representation can be used for tasks such as image coding, person identification, 3D pose recovery, gender recognition, and expression recognition. Experimental results are presented for a database of 690 face images obtained under widely varying conditions of 3D pose, lighting, and facial expression. The system performs well on all the tasks listed above     

结合形变模型与图像修复的人脸姿态矫正

目的 人脸姿态偏转是影响人脸识别准确率的一个重要因素,本文利用3维人脸重建中常用的3维形变模型以及深度卷积神经网络,提出一种用于多姿态人脸识别的人脸姿态矫正算法,在一定程度上提高了大姿态下人脸识别的准确率。方法 对传统的3维形变模型拟合方法进行改进,利用人脸形状参数和表情参数对3维形变模型进行建模,针对面部不同区域的关键点赋予不同的权值,加权拟合3维形变模型,使得具有不同姿态和面部表情的人脸图像拟合效果更好。然后,对3维人脸模型进行姿态矫正并利用深度学习对人脸图像进行修复,修复不规则的人脸空洞区域,并使用最新的局部卷积技术同时在新的数据集上重新训练卷积神经网络,使得网络参数达到最优。结果 在LFW（labeled faces in the wild）人脸数据库和StirlingESRC（Economic Social Research Council）3维人脸数据库上,将本文算法与其他方法进行比较,实验结果表明,本文算法的人脸识别精度有一定程度的提高。在LFW数据库上,通过对具有任意姿态的人脸图像进行姿态矫正和修复后,本文方法达到了96.57%的人脸识别精确度。在StirlingESRC数据库上,本文方法在人脸姿态为±22°的情况下,人脸识别准确率分别提高5.195%和2.265%;在人脸姿态为±45°情况下,人脸识别准确率分别提高5.875%和11.095%;平均人脸识别率分别提高5.53%和7.13%。对比实验结果表明,本文提出的人脸姿态矫正算法有效提高了人脸识别的准确率。结论 本文提出的人脸姿态矫正算法,综合了3维形变模型和深度学习模型的优点,在各个人脸姿态角度下,均能使人脸识别准确率在一定程度上有所提高。     

基于脊谷特征提取的三维人脸识别

针对三维人脸数据庞大及识别效率低的问题,提出采用提取脊点及谷点表征人脸。脊点和谷点作为曲面局部区域内主曲率沿主方向变化的极值点,能够很好地表征三维人脸特征。对三维人脸提取脊点模型和谷点模型,通过对它们栅格化后生成对应的空间分布密度直方图实现人脸粗匹配,采用计算LTS-Hausdorff距离实现人脸的精确匹配。在GavabDB三维人脸库的实验结果表明,该方法具有较高的识别率。