基于稀疏表示的概率子空间聚类人脸识别

针对子空间聚类应用中高达数以百万计信号的数据集合问题,为了实现快速聚类,提出了一种基于稀疏表示的概率子空间聚类算法。首先,每个信号由一个稀疏组合的基本元素(原子)表示,这些原子构成了字典矩阵的列;接着利用稀疏表示集推导出一个混合模式的原子和信号的共生矩阵;最后,通过共生矩阵的非负矩阵分解(NNMF)得到混合模式的组件,并根据最大似然(ML)准则估算每个信号的子空间。在YaleB人脸数据库上的实验结果表明,与其他几种最先进的方法相比,所提方法取得了较好的聚类精度。     

基于Gabor多通道加权优化与稀疏表征的人脸识别方法

稀疏表征理论在模式识别中的应用引起广泛的关注。在用稀疏表征方法研究人脸识别问题中,为了使得表征系数矢量具有更为显著的稀疏性,该文提出一种Gabor稀疏表征分类(Gabor Sparse Representation Classification, GSRC)算法,该算法利用Gabor局部特征构造字典,增强算法对外界环境变化的鲁棒性。GSRC算法对所有的Gabor特征等同对待,通过进一步考虑不同Gabor特征对识别的不同贡献,该文提出了一种加权多通道Gabor稀疏表征分类(WMC-GSRC)算法,该算法通过引入Gabor多通道模型,提取不同通道的Gabor特征分别构造字典和稀疏表征分类器,在决策级执行分类器的加权融合得到识别结果。通过在ORL, AR和FERET人脸库上的实验结果验证了该文算法的有效性。     

Sparse representation for face recognition by discriminative low-rank matrix recovery

This paper proposes a discriminative low-rank representation (DLRR) method for face recognition in which both the training and test samples are corrupted owing to variations in occlusion and disguise. The proposed method extends the sparse representation-based classification algorithm by incorporating the low-rank structure of data representation. The DLRR algorithm recovers a clean dictionary with enhanced discrimination ability from the corrupted training samples for sparse representation. Simultaneously, it learns a low-rank projection matrix to correct corrupted test samples by projecting them onto their corresponding underlying subspaces. The dictionary elements from different classes are encouraged to be as independent as possible by regularizing the structural incoherence of the original training samples. This leads to a compact representation of a corrected test sample by a linear combination of more dictionary elements from the corrected class. The experimental results on benchmark databases show the effectiveness and robustness of our face recognition technique.     

Adjusting samples for obtaining better l2-norm minimization based sparse representation

l₂-norm sparse representation (l₂-SR) based face recognition method has attracted increasing attention due to its excellent performance, simple algorithm and high computational efficiency. However, one of the drawbacks of l₂-SR is that the test sample may be conspicuous difference from the training samples even from the same class and thus the method shows poor robustness. Another drawback is that l₂-SR does not perform well in identifying the training samples that are trivial in correctly classifying the test sample. In this paper, to avoid the above imperfection, we proposed a novel l₂-SR. We first identifies the training samples that are important in correctly classifying the test sample and then neglects components that cannot be represented by the training samples. The proposed method also involve in-depth analysis of l₂-SR and provide novel ideas to improve previous methods. Experimental results on face datasets show that the proposed method can greatly improve l₂-SR.     

Face Recognition Using Dense SIFT Feature Alignment

This paper addresses face recognition problem in a more challenging scenario where the training and test samples are both subject to the visual variations of poses,expressions and misalignments.We employ dense Scale-invariant feature transform (SIFT) feature matching as a generic transformation to roughly align training sampies;and then identify input facial images via an improved sparse representation model based on the aligned training samples.Compared with previous methods,the extensive experimental results demonstrate the effectiveness of our method for the task of face recognition on three benchmark datasets.     

基于判别性降维的字典学习在人脸识别中的应用

针对目前大多数人脸识别方法只能单独实施降维或者字典学习而不能完全利用训练样本判别信息的问题,提出了基于判别性降维的字典学习方法,通过联合降维与字典学习使得投影矩阵和字典更好地相互拟合,从而可以获得更高效的人脸分类系统。所提方法的有效性在AR及MPIE两大通用人脸数据库上得到了验证,实验结果表明,相比于几种先进的线性表示方法,所提算法取得了更高的识别率,特别当训练样本数很少的时候,识别效果更佳。     

基于稀疏表示的两级图像去噪

在噪声较严重的情况下对图像进行恢复,至今仍是一个挑战。该文提出一种基于图像稀疏表示的去噪方法。在原子库训练中,引入基于相关系数的匹配准则和原子库裁剪方案,很好地处理了图像结构提取和人为噪声抑制之间的矛盾。实验结果表明,该方法在主客观去噪性能上较同类方法有了显著的提高,在噪声强度较大的情况下,获得了比当前先进方法更好的主客观图像恢复质量。     

基于Fisher判别字典学习的说话人识别

稀疏表示已成功应用于说话人识别领域。在稀疏表示中,构造好的字典起着重要的作用。该文将Fisher准则的结构化字典学习方法引入说话人识别系统。在判别字典的学习过程中,每一个字典对应一个类标签,因此同类别训练样本的重构误差较小。同时,保证训练样本的稀疏编码系数类内误差最小,类间误差最大。在NIST SRE 2003数据库上,实验结果表明该算法得到的等错误率是7.62%,基于余弦距离打分的i-vector的等错误率是6.7%。当两个系统融合后,得到的等错误率是5.07%。     

图约束字典和加权稀疏表示人脸超分辨率算法

针对低分辨率、低质量人脸图像重建问题,提出了一种新的基于稀疏表示的人脸超分辨率算法。在训练阶段,人脸的位置特征被用于保持人脸块的全局信息,人脸块间的几何结构被用于保持高低分辨率超完备冗余字典的流形结构,从而提高字典的表达能力;在重建阶段,K近邻加权稀疏表示被用于消除稀疏编码噪声,以提高高分辨率人脸图像重建系数的精度。实验结果表明,提出的方法取得了较好的主客观质量。     

基于稀疏稠密结构表示与在线鲁棒字典学习的视觉跟踪

L1跟踪对适度的遮挡具有鲁棒性,但是存在速度慢和易产生模型漂移的不足。为了解决上述两个问题,该文首先提出一种基于稀疏稠密结构的鲁棒表示模型。该模型对目标模板系数和小模板系数分别进行L2范数和L1范数正则化增强了对离群模板的鲁棒性。为了提高目标跟踪速度,基于块坐标优化原理,用岭回归和软阈值操作建立了该模型的快速算法。其次,为降低模型漂移的发生,该文提出一种在线鲁棒的字典学习算法用于模板更新。在粒子滤波框架下,用该表示模型和字典学习算法实现了鲁棒快速的跟踪方法。在多个具有挑战性的图像序列上的实验结果表明：与现有跟踪方法相比,所提跟踪方法具有较优的跟踪性能。     

Matching pursuit shrinkage in Hilbert spaces

In this paper, we study a variant of the matching pursuit named matching pursuit shrinkage. Similar to the matching pursuit it seeks for an approximation of a datum living in a Hilbert space by a sparse linear expansion in a countable set of atoms. The difference with the usual matching pursuit is that, once an atom has been selected, we do not erase all the information along the direction of this atom. Doing so, we can evolve slowly along that direction. The goal is to attenuate the negative impact of bad atom selections.We analyze the link between the shrinkage function used by the algorithm and the fact that the result belongs to l², l¹ and l⁰ space. Experimental results are also reported to show the potential application of the proposed algorithm.     

一种基于稠密SIFT特征对齐的稀疏表达人脸识别算法

该文针对人脸图像受到非刚性变化的影响,如旋转、姿态以及表情变化等,提出一种基于稠密尺度不变特征转换(SIFT)特征对齐(Dense SIFT Feature Alignment, DSFA)的稀疏表达人脸识别算法。整个算法包含两个步骤：首先利用DSFA方法对齐训练和测试样本;然后设计一种改进的稀疏表达模型进行人脸识别。为加快DSFA步骤的执行速度,还设计了一种由粗到精的层次化对齐机制。实验结果表明：在ORL,AR和LFW 3个典型数据集上,该文方法都获得了最高的识别精度。该文方法比传统稀疏表达方法在识别精度上平均提高了4.3%,同时提高了大约6倍的识别效率。     

Context-aware joint dictionary learning for color image demosaicking

Most digital cameras are overlaid with color filter arrays (CFA) on their electronic sensors, and thus only one particular color value would be captured at every pixel location. When producing the output image, one needs to recover the full color image from such incomplete color samples, and this process is known as demosaicking. In this paper, we propose a novel context-constrained demosaicking algorithm via sparse-representation based joint dictionary learning. Given a single mosaicked image with incomplete color samples, we perform color and texture constrained image segmentation and learn a dictionary with different context categories. A joint sparse representation is employed on different image components for predicting the missing color information in the resulting high-resolution image. During the dictionary learning and sparse coding processes, we advocate a locality constraint in our algorithm, which allows us to locate most relevant image data and thus achieve improved demosaicking performance. Experimental results show that the proposed method outperforms several existing or state-of-the-art techniques in terms of both subjective and objective evaluations.     

Locality-sensitive kernel sparse representation classification for face recognition

In this paper a new classification method called locality-sensitive kernel sparse representation classification (LS-KSRC) is proposed for face recognition. LS-KSRC integrates both sparsity and data locality in the kernel feature space rather than in the original feature space. LS-KSRC can learn more discriminating sparse representation coefficients for face recognition. The closed form solution of the l₁-norm minimization problem for LS-KSRC is also presented. LS-KSRC is compared with kernel sparse representation classification (KSRC), sparse representation classification (SRC), locality-constrained linear coding (LLC), support vector machines (SVM), the nearest neighbor (NN), and the nearest subspace (NS). Experimental results on three benchmarking face databases, i.e., the ORL database, the Extended Yale B database, and the CMU PIE database, demonstrate the promising performance of the proposed method for face recognition, outperforming the other used methods.     

Complex SAR Image Compression Using Entropy-Constrained Dictionary Learning and Universal Trellis Co ded Quantization

In this paper, an Entropy-constrained dic-tionary learning algorithm (ECDLA) is introduced for e?-cient compression of Synthetic aperture radar (SAR) com-plex images. ECDLA RI encodes the Real and imaginary parts of the images using ECDLA and sparse representa-tion, and ECDLA AP encodes the Amplitude and phase parts respectively. When compared with the compression method based on the traditional Dictionary learning al-gorithm (DLA), ECDLA RI improves the Signal-to-noise ratio (SNR) up to 0.66dB and reduces the Mean phase error (MPE) up to 0.0735 than DLA RI. With the same MPE, ECDLA AP outperforms DLA AP by up to 0.87dB in SNR. Furthermore, the proposed method is also suitable for real-time applications.     

Kernel dictionary learning based discriminant analysis

Sparse representation based classification (SRC) has been successfully applied in many applications. But how to determine appropriate features that can best work with SRC remains an open question. Dictionary learning (DL) has played an import role in the success of sparse representation, while SRC treats the entire training set as a structured dictionary. In addition, as a linear algorithm, SRC cannot handle the data with highly nonlinear distribution. Motivated by these concerns, in this paper, we propose a novel feature learning method (termed kernel dictionary learning based discriminant analysis, KDL-DA). The proposed algorithm aims at learning a projection matrix and a kernel dictionary simultaneously such that in the reduced space the sparse representation of the data can be easily obtained, and the reconstruction residual can be further reduced. Thus, KDL-DA can achieve better performances in the projected space. Extensive experimental results show that our method outperforms many state-of-the-art methods.     

Feature discovering for image classification via wavelet-like pattern decomposition

In this paper, we propose a feature discovering method incorporated with a wavelet-like pattern decomposition strategy to address the image classification problem. In each level, we design a discriminative feature discovering dictionary learning (DFDDL) model to exploit the representative visual samples from each class and further decompose the commonality and individuality visual patterns simultaneously. The representative samples reflect the discriminative visual cues per class, which are beneficial for the classification task. Furthermore, the commonality visual elements capture the communal visual patterns across all classes. Meanwhile, the class-specific discriminative information can be collected by the learned individuality visual elements. To further discover the more discriminative feature information from each class, we then integrate the DFDDL into a wavelet-like hierarchical architecture. Due to the designed hierarchical strategy, the discriminative power of feature representation can be promoted. In the experiment, the effectiveness of proposed method is verified on the challenging public datasets.     

基于Fisher约束和字典对的图像分类

基于稀疏表示的分类方法由于其所具有的简单性和有效性获得了研究者的广泛关注,然而如何建立字典原子与类别信息间的联系仍然是一个重要的问题,与此同时大部分稀疏表示分类方法都需要求解受范数约束的优化问题,使得分类任务的计算较复杂。为解决上述问题,该文提出一种新的基于Fisher约束的字典对学习方法。新方法联合学习结构化综合字典和结构化解析字典,然后通过样本在解析字典上的映射直接求解稀疏系数矩阵;同时采用Fisher判别准则编码系数使系数具有一定的判别性。最后将新方法应用到图像分类中,实验结果表明新方法在提高分类准确率的同时还大大降低了计算复杂度,相较于现有方法具有更好的性能。