基于Gabor特征的稀疏表示纹理分割研究

稀疏表示和字典学习在图像去噪、图像重建和模式识别等应用上取得了良好的效果,其利用稀疏系数和重构误差来作为模式分类的判别准则。稀疏表示纹理分割方法是将图像分割问题转换为像素点的分类问题。但通常稀疏表示分类方法是基于图像块特征,难以准确表征图像纹理信息。为了解决上述问题,提出基于Gabor特征的稀疏表示纹理分割方法。因为Gabor特征对图像纹理信息的鲁棒性,算法首先从每类纹理中选择一些像素点作为训练样本,计算其不同尺度和方向下的Gabor特征,将其作为初始化字典,通过判别性的字典学习算法(D-KSVD)更新字典,该字典学习算法在KSVD基础上使得字典更具有类别判别能力,最后以待分割图像的每个像素点作为测试样本,计算其Gabor特征。利用OMP算法得到测试样本在字典下的稀疏系数,根据稀疏系数得到类标签,进而对像素点进行分类,完成分割。通过在Brodatz纹理库上的实验结果表明,该方法有效提高了稀疏表示算法对纹理图像分割的正确率。     

复杂场景下结合SIFT与核稀疏表示的交通目标分类识别

针对复杂场景下的交通目标分类识别难点,提出一种基于尺度不变特征转换(SIFT)与核稀疏表示的分类识别算法.该算法首先利用SIFT分别提取训练样本和待测目标局部特征信息,通过核方法将特征样本映射到核空间,构建过完备字典,最后通过待测目标在字典中的稀疏度与重构误差对交通目标类别进行判定.同时,分析了随机投影下的核稀疏表示分类与特征维数之间的关系.实验结果表明,与SVM、稀疏表示分类(SRC)相比,该方法增强了交通目标特征层的类判别能力,具有较好的识别率和鲁棒性.     

基于Gabor特征和字典学习的高斯混合稀疏表示图像识别

为了克服图像识别中光照,姿态等变化带来的识别困难,同时提高稀疏表示图像识别的鲁棒性,本文提出了一种基于Gabor特征和字典学习的高斯混合稀疏表示图像识别算法.高斯混合稀疏表示是基于最大似然估计准则,将稀疏保真度表示为余项的最大似然函数,最终识别问题转化为求解加权范数的优化逼近问题.本文算法首先提取图像的Gabor特征;然后对Gabor特征集进行字典学习,由于在学习过程中引入了Fisher准则作为约束,学习得到具有类别标签的新字典;最后使用高斯混合稀疏表示识别方法进行分类识别.在3个公开数据库(人脸数据库AR库和FERET库以及USPS手写数字库)上的实验结果验证了该算法的有效性和鲁棒性.     

先验采样约束结合扩展字典的细化稀疏识别算法

为解决可能存在遮挡环境下的模式识别问题,提出先验采样约束结合扩展遮挡字典的细化稀疏识别算法。针对训练样本无法包含测试样本遮挡变化的情况,首先需要构造遮挡字典（墨镜、围巾等）,进而利用先验局部采样子模块稀疏表示分类原理判断可能存在的测试样本遮挡模式;然后对未被遮挡的局部子模块利用Borda计数投票方式,依据每类残差大小分配给不同的票数,计算样本类别信息;其次根据遮挡模式结果,利用全局稀疏表示通过构造样本遮挡扩展字典对测试样本进行全局分类投票;最后将两次分类投票结果进行融合,最终实现是否存在遮挡环境下的精细模式判别。实验结果表明,本文算法不仅能够给出准确的模式类别,还能给出遮挡类别信息,可得到精细化识别结果。      

基于块稀疏贝叶斯学习的SAR图像目标方位角估计方法

提出了一种基于块稀疏贝叶斯学习的合成孔径雷达（Synthetic aperture radar,SAR）图像目标方位角估计方法。SAR图像具有较强的方位角敏感性,因此对于具有某一方位角的SAR图像仅能与其具有相近方位角的样本具有较高的相关性。方法基于稀疏表示的基本思想,首先对所有训练样本按照方位角顺序排列为全局字典。在此条件下,待估计样本在该字典上的线性表示系数具有块稀疏特性,即非零表示系数主要聚集在字典上的某一局部区域。求解得到的块稀疏位置包含的训练样本可以有效地反映待估计样本的方位角信息。采用块稀疏贝叶斯学习（Block sparse Bayesian learning, BSBL）算法求解全局字典上的稀疏表示系数,并根据具有最小重构误差的原则获得最佳的局部分块。在获取最佳分块的基础上,方位角计算方法采用线性加权的方式综合了该分块区间内所有训练样本的方位角信息从而获得更为稳健的估计结果。所提出的方法在充分考察SAR图像方位角敏感性的基础上,综合运用局部区间内样本的有效信息,避免了基于单一样本估计的不确定性。为了验证所提出方法的有效性,基于Moving and stationary target acquisition and recognition （MSTAR）数据集进行了方位角估计实验并与几类经典方法进行对比分析。实验结果验证了所提出方法的性能优势。     

基于Gabor低秩恢复稀疏表示分类的人脸图像识别方法

针对含光照、表情、姿态、遮挡等误差或被噪声污染的人脸图像的识别问题,本文提出一种基于Gabor低秩恢复稀疏表示分类的人脸图像识别方法。该方法首先用低秩矩阵恢复算法求得训练样本图像对应的误差图像;然后,对每一个训练样本图像及其对应的误差图像进行Gabor变换,得到相应的Gabor特征向量,并将这些Gabor特征向量组成一个Gabor特征字典;进而,计算测试样本图像Gabor特征向量在该Gabor特征字典下的稀疏表示系数,并用该稀疏表示系数和Gabor特征字典,对测试样本图像的Gabor特征向量进行类关联重构,同时计算相应的类关联重构误差。最后,根据测试样本图像Gabor特征向量的类关联重构误差,实现对测试样本图像的分类识别。在CMU PIE、Extend-ed Yale B和AR数据库上的实验结果表明,本文提出的人脸图像识别方法具有较高的识别率和较强的抗干扰能力。     

原子稀疏结合块结构稀疏的联合表示图像识别算法

针对结构稀疏表示识别算法中稀疏准则的选择以及字典内块的划分两个重要问题,提出两种改进的结构稀疏表示识别算法。首先,针对结构稀疏准则会出现较多系数不为零的情况,提出将结构稀疏准则与原子稀疏准则相结合的思路,包括并行和串行两种结合方式。并行结合是将两者以加权求和的方式同时作为稀疏表示的判别准则进行分类,串行结合则是在结构稀疏表示后,通过重组字典,再对测试样本进行原子稀疏表示实现分类。然后,针对字典中类内样本的块划分问题,提出基于MLP的结构稀疏表示识别算法,先将类内样本经过MLP的划分,保证各个分块分别位于低维的线性子空间中,再进行结构稀疏表示的分类。实验结果证明两种改进的结构稀疏表示识别算法的有效性。      

压缩感知稀疏表示在雷达目标识别中的应用

高分辨距离像(HRRP)目标识别算法很多,在其利用高分辨距离像蕴含的目标结构信息的同时,也需要面对数据量巨大的难题.事实上,尽管高分辨距离像数据量巨大,但却是稀疏的,然而利用其稀疏特性进行识别的方法却不多.为此,提出了一种基于压缩感知稀疏表示方法实现目标识别的算法.该算法首先采用遗传正交匹配追踪(OMP)算法对一维距离像训练样本进行稀疏分解以获得类别字典,然后根据类别字典分析测试样本的重构误差实现目标识别.仿真实验证明,所提算法简捷、识别率更高,相较于常规算法识别率提高最多可达20％,并且在受到噪声干扰情况下依然能够稳健地识别目标.     

基于压缩感知的SAR图像目标识别

提出一种基于压缩感知的合成孔径雷达图像目标识别方法,将目标识别问题转化为稀疏表示的近似求解问题。该方法利用测试样本在全体训练样本基下的稀疏性,实现样本间的近似稀疏表示。通过考察稀疏系数主要集中于样本真实类别之上的分布特性,研究了稀疏系数本身对目标类别具有的可区分能力,最后基于稀疏系数的分布特性设计分类算法完成目标识别。基于MSTAR数据中三类目标的实验证明,与目前已有的几种典型方法相比,该方法可以取得更高的识别率,是一种有效的合成孔径雷达图像目标识别方法。     

基于样本-扩展差分模板的联合双稀疏表示人脸识别

在人脸识别中,每类数据分别位于由字典形成的高维空间中的多个低维线性子空间,考虑到这一结构信息对识别起到一定支持作用,利用块结构稀疏表示进行人脸识别。针对训练图像不能涵盖测试条件下的人脸变化这个问题,提出基于样本-扩展差分模板的联合双稀疏表示识别算法。它通过构造样本-扩展差分模板来表示训练样本与测试样本之间可能存在的差异,这些类内差异信息可被不同的类别所共享,即任何一类人脸图像的类内差异可表示为其他类别类内差异图像的原子稀疏线性组合。这样识别问题被转换为在训练样本空间和扩展差分模板空间寻找测试样本的块稀疏与原子稀疏的联合双稀疏表示。在AR和Extended Yale B数据库上的实验结果表明,在具有光照、表情变化和遮挡的情况下,本文提出的识别算法具有更好的有效性和鲁棒性。     

Block-based histogram of optical flow for isolated sign language recognition

In this paper, we propose a block-based histogram of optical flow (BHOF) to generate hand representation in sign language recognition. Optical flow of the sign language video is computed in a region centered around the location of the detected hand position. The hand patches of optical flow are segmented into M spatial blocks, where each block is a cuboid of a segment of a frame across the entire sign gesture video. The histogram of each block is then computed and normalized by its sum. The feature vector of all blocks are then concatenated as the BHOF sign gesture representation. The proposed method provides a compact scale-invariant representation of the sign language. Furthermore, block-based histogram encodes spatial information and provides local translation invariance in the extracted optical flow. Additionally, the proposed BHOF also introduces sign language length invariancy into its representation, and thereby, produce promising recognition rate in signer independent problems.     

基于时空压缩特征表示学习的毫米波雷达手势识别算法

针对现有无线射频信号的手势识别研究中的数据预处理和特征利用问题,该文提出一种用于调频连续波(FMCW)雷达的时空压缩特征表示学习的手势识别算法。首先对手部反射的毫米波雷达回波信号的距离-多普勒(RD)图进行静态干扰去除和动目标点筛选,减少杂波对手势信号的干扰,同时减少计算数据量;然后提出一种压缩手势时空特征的表示方法,利用动目标点的主导速度来表示手势的运动特征,实现多维特征的压缩映射,并保留手势运动的关键特征信息;最后设计了一个单通道的卷积神经网络(CNN)来学习和分类多维手势特征信息并应用于多用户和多位置的手势识别。实验结果表明,与现有其他手势识别算法相比,该文提出的手势识别方法在识别精度、实时性以及泛化能力上都具有明显的优势。     

On an algorithm for Vision-based hand gesture recognition

A vision-based static hand gesture recognition method which consists of preprocessing, feature extraction, feature selection and classification stages is presented in this work. The preprocessing stage involves image enhancement, segmentation, rotation and filtering. This work proposes an image rotation technique that makes segmented image rotation invariant and explores a combined feature set, using localized contour sequences and block-based features for better representation of static hand gesture. Genetic algorithm is used here to select optimized feature subset from the combined feature set. This work also proposes an improved version of radial basis function (RBF) neural network to classify hand gesture images using selected combined features. In the proposed RBF neural network, the centers are automatically selected using k-means algorithm and estimated weight matrix is recursively updated, utilizing least-mean-square algorithm for better recognition of hand gesture images. The comparative performances are tested on two indigenously developed databases of 24 American sign language hand alphabet.     

Research on unified recognition model and algorithm for multi-modal gestures

In gesture recognition,static gestures,dynamic gestures and trajectory gestures are collectively known as multi-modal gestures.To solve the existing problem in different recognition methods for different modal gestures,a unified recognition algorithm is proposed.The angle change data of the finger joints and the movement of the centroid of the hand were acquired respectively by data glove and Kinect.Through the preprocessing of the multi-source heterogeneous data,all hand gestures were considered as curves while solving hand shaking,and a uniform hand gesture recognition algorithm was established to calculate the Pearson correlation coefficient between hand gestures for gesture recognition.In this way,complex gesture recognition was transformed into the problem of a simple comparison of curves similarities.The main innovations:1) Aiming at solving the problem of multi-modal gesture recognition,an unified recognition model and a new algorithm is proposed;2) The Pearson correlation coefficient for the first time to construct the gesture similarity operator is improved.By testing 50 kinds of gestures,the experimental results showed that the method presented could cope with intricate gesture interaction with the 97.7% recognition rate.     

Distance based kernels for video tensors on product of Riemannian matrix manifolds

In this paper, we explore the inherent geometry of video tensors by modeling them as points in product of Riemannian matrix manifolds. A video tensor is decomposed into three modes (factors) using matrix unfolding operation and each mode is represented as a point in a product space of Grassmannian and symmetric positive definite (SPD) matrix manifold. Hence a video is represented as a point in the Cartesian product of three such product spaces. Being a manifold valued (non-Euclidean) representation, application of several state-of-the-art Euclidean machine learning algorithms lead to inferior results. To overcome this, we propose positive definite kernels which map the points from product manifold space to Hilbert space. The proposed kernel functions implicitly make use of geodesic distance on product manifold to obtain a similarity measure and generate a kernel-gram matrix. In addition, we generate a discriminative feature representation for each manifold valued point using kernel-gram matrix diagonalization. Classification is performed in a sparse framework. The proposed methodology is tested over three publicly available datasets for hand gesture, traffic signal and sign language recognition. Experimentation performed over these datasets show that the proposed methodology is powerful in terms of classification accuracy in comparison with the state-of-the-art methods.     

基于双分类器的自适应单双手手势识别

针对传统卷积神经网络(CNN)中仅有对单手手势语义进行识别的算法和深度学习手势识别算法中CNN的收敛性差和识别精度低的问题,提出了一种基于两个分类器的自适应单双手手势识别算法以对单手和双手进行识别.该算法的核心是联合两个分类器进行单双手手势识别.首先,采用手数分类器对手势进行分割分组预测,将手势识别转化成部分手势图像识...     

Hand gesture understanding by weakly-supervised fusing shallow/deep image attributes

Accurately recognizing human hand gestures is a useful component in many modern intelligent systems, such as identification authentication, human–computer interaction, and sign language recognition. Conventional approaches are typically based on shallow visual features and relatively simple backgrounds, which cannot readily recognize partially occluded hand gestures with sophisticated backgrounds. In this work, we propose a unified hand gesture recognition framework by optimally fusing a set of shallow/deep finger-level image attributes, based on which a weakly-supervised ranking algorithm is designed to select semantically salient regions for gesture understanding. More specifically, given a rich number of hand gesture images, we employ the well-known BING object proposal generator to extract hundreds of object patches that potentially draw human visual attention. Since the hundreds of object patches are still too many for building an effective recognition system, a weakly-supervised metric is proposed to rank them by extracting multiple shallow/deep features. And visual semantics are encoded at region-level by transferring the image-level semantic tags into various human gesture image regions by a weakly-supervised learning paradigm Apparently, the top-ranking highly salient object patches are highly indicative to human visual perception of human hand gesture, Thus we extract their ImageNet-CNN features and further concatenate them. Finally, the concatenated deep feature is fed into a multi-class SVM for classifying each hand gesture image into a particular type. Comprehensive experimental validations have demonstrated the effectiveness and robustness of our proposed hybrid-feature-based hand gesture categorization.     

Viewpoint-independent hand gesture recognition with Kinect

The advent and popularity of Kinect provide new choice and opportunity for hand gesture recognition research. Aiming at the effective, accurate and freely used hand gesture recognition with Kinect, this paper presents a viewpoint-independent hand gesture recognition method. Firstly, based on the rules about gesturers posture under optimal viewpoint, the gesturers point clouds are built and transformed to the optimal viewpoint with the exploration of the joint information. Then Laplacian-based contraction is applied to extract representative skeletons from the transformed point clouds. A novel partition-based algorithm is further proposed to recognize the gestures. The promising experiment results show that the proposed method performs satisfyingly on scale and rotation variant in HGR with robustness and high accuracy.     

Real-time Hand Gesture Recognition from Depth Images Using Convex Shape Decomposition Method

Hand gesture recognition is one of the most natural and intuitive ways to communicate between people and machines, since it closely mimics how human interact with each other. This paper presents a novel method for real-time markerless hand gesture recognition from depth images. The proposed method encompasses a collection of techniques that enable the detection, segmentation and recognition of hand gestures. A Hand detection and location method is employed using the depth information acquired from a depth sensor. Then, the hand is robustly segmented in cluttered background without any marker around. A convex shape decomposition method based on Radius Morse function is proposed for hand shape decomposition in real-time. Hand palm, fingertips and hand skeleton are recognized based on the hand shape decomposition and hand features. Moreover, we present a method for recognition of two-hand gestures. Representative experimental results demonstrate qualitatively and quantitatively that accurate hand gesture recognition can be achieved for real-time applications.     

基于“面部表情+手”的混合手势交互技术

为克服单一输入形式存在的交互缺点,融合手部移动和面部表情两种输入方式的交互特性,将手部移动和面部表情动作相结合,提出了基于“面部表情+手”的混合手势交互技术。混合手势交互技术将7种面部表情和手部移动组合起来,通过手部移动和面部表情识别操控计算机执行一系列目标选择任务。设计的实验中,手部移动用于操控鼠标光标移动,面部表情识别替代鼠标的点击操作用于选中目标按钮。根据设计的多种目标选择任务,详细分析混合手势交互技术的识别错误率和平均识别时间。结果表明,“面部表情+手”的混合手势交互技术的识别准确率可达93.81%,平均识别时间可达2921 ms,完全满足日常的人机交互需求。