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Copyright of Rolling Stock (1002-7602) is the property of Rolling Stock Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Learning a fast and discriminative patch descriptor is a challenging topic in computer vision. Recently, many existing works focus on training various descriptor learning networks by minimizing a triplet loss (or its variants), which is expected to decrease the distance between each positive pair and increase the distance between each negative pair. However, such an expectation has to be lowered due to the non-perfect convergence of network optimizer to a local solution. Addressing this problem and the open computational speed problem, we propose a Descriptor Distillation framework for local descriptor learning, called DesDis, where a student model gains knowledge from a pre-trained teacher model, and it is further enhanced via a designed teacher-student regularizer. This teacher-student regularizer is to constrain the difference between the positive (also negative) pair similarity from the teacher model and that from the student model, and we theoretically prove that a more effective student model could be trained by minimizing a weighted combination of the triplet loss and this regularizer, than its teacher which is trained by minimizing the triplet loss singly. Under the proposed DesDis, many existing descriptor networks could be embedded as the teacher model, and accordingly, both equal-weight and light-weight student models could be derived, which outperform their teacher in either accuracy or speed. Experimental results on 3 public datasets demonstrate that the equal-weight student models, derived from the proposed DesDis framework by utilizing three typical descriptor learning networks as teacher models, could achieve significantly better performances than their teachers and several other comparative methods. In addition, the derived light-weight models could achieve 8 times or even faster speeds than the comparative methods under similar patch verification performances. [ABSTRACT FROM AUTHOR]

Few-shot learning for image classification comes up as a hot topic in computer vision, which aims at fast learning from a limited number of labeled images and generalize over the new tasks. In this paper, motivated by the idea of Fisher Score, we propose a Discriminative Local Descriptors Attention model that uses the ratio of intra-class and inter-class similarity to adaptively highlight the representative local descriptors without introducing any additional parameters, while most of the existing local descriptors based methods utilize the neural networks that inevitably involve the tedious parameter tuning. Experiments on four benchmark datasets show that our method achieves higher accuracy compared with the state-of-art approaches for few-shot learning. Specifically, our method is optimal on the CUB-200 dataset, and outperforms the second best competitive algorithm by 4.12 % and 0.49 % under the 5-way 1-shot and 5-way 5-shot settings, respectively. [ABSTRACT FROM AUTHOR]

We construct a novel descriptor called anisotropic wavelet energy decomposition descriptor (AWEDD) for non-rigid shape analysis, based on anisotropic diffusion geometry. We first extend the Dirichlet energy of the vertex coordinate function to an anisotropic version, then use multiscale anisotropic spectral manifold wavelets to decompose the Dirichlet energy to all vertices and collect local energy at each vertex to form AWEDD. AWEDD simultaneously encodes multiscale extrinsic and intrinsic shape features, which are more informative and robust than purely intrinsic or extrinsic descriptors. And the introduction of anisotropy endows AWEDD with stronger abilities of feature discrimination and intrinsic symmetry identification. Our results demonstrate that AWEDD is more discriminative than current state-of-the-art descriptors. In addition, we show that AWEDD is an excellent choice of the initial inputs for various shape analysis approaches, such as functional map pipelines and deep convolutional architectures. [ABSTRACT FROM AUTHOR]

Multi-scale feature fusion has been widely used in handcrafted descriptors, but has not been fully explored in deep learning-based descriptor extraction. Simple concatenation of descriptors of different scales has not been successful in significantly improving performance for computer vision tasks. In this paper, we propose a novel convolutional neural network, based on center-surround adaptive multi-scale feature fusion. Our approach enables the network to focus on different center-surround scales, resulting in improved performance. We also introduce a novel regularization technique that uses second-order similarity to constrain the learning of local descriptors, based on the symmetric property of the similarity matrix. The proposed method outperforms single-scale or simple-concatenation descriptors on two datasets and achieves state-of-the-art results on the Brown dataset. Furthermore, our method demonstrates excellent generalization ability on the HPatches dataset. Our code is released on GitHub: https://github.com/Leung-GD/AFSRNet/tree/main. [ABSTRACT FROM AUTHOR]

Depending on the context of interest, an anomaly is defined differently. In the case when a video event isn’t expected to take place in the video, it is seen as anomaly. It can be difficult to describe uncommon events in complicated scenes, but this problem is frequently resolved by using high-dimensional features as well as descriptors. There is a difficulty in creating reliable model to be trained with these descriptors because it needs a huge number of training samples and is computationally complex. Spatiotemporal changes or trajectories are typically represented by features that are extracted. The presented work presents numerous investigations to address the issue of abnormal video detection from crowded video and its methodology. Through the use of low-level features, like global features, local features, and feature features. For the most accurate detection and identification of anomalous behavior in videos, and attempting to compare the various techniques, this work uses a more crowded and difficult dataset and require light weight for diagnosing anomalies in objects through recording and tracking movements as well as extracting features; thus, these features should be strong and differentiate objects. After reviewing previous works, this work noticed that there is more need for accuracy in video modeling and decreased time, and since attempted to work on real-time and outdoor scenes. [ABSTRACT FROM AUTHOR]

Deep learning has been successfully exploited to various computer vision tasks, which depend on abundant annotations. The core goal of few-shot learning, in contrast, is to learn a classifier to recognize new classes from only a few labeled examples that produce a key challenge of visual recognition. However, most of the existing methods often adopt image-level features or local monodirectional manner-based similarity measures, which suffer from the interference of non-dominant objects. To tackle this limitation, we propose a Bi-Directional Local Alignment (BDLA) approach for the few-shot visual classification problem. Specifically, building upon the episodic learning mechanism, we first adopt a shared embedding network to encode the 3D tensor features with semantic information, which can effectively describe the spatial geometric representation of the image. Afterwards, we construct a forward and a backward distance by exploring the nearest neighbor search to determine the semantic region-wise feature corresponding to each local descriptor of query sets and support sets. The bi-directional distance can encourage the alignment between similar semantic information while filtering out the interference information. Finally, we design a convex combination to merge the bi-directional distance and optimize the network in an end-to-end manner. Extensive experiments also show that our proposed approach outperforms several previous methods on four standard few-shot classification datasets. [ABSTRACT FROM AUTHOR]

Thermal infrared imaging is attracting much attention due to its strength against illuminance variation. However, because of the spectral difference between thermal infrared images and RGB images, the existing research on self-supervised monocular depth estimation has performance limitations. Therefore, in this study, we propose a novel Self-Guided Framework using a Pseudolabel predicted from RGB images. Our proposed framework, which solves the problem of appearance matching loss in the existing framework, transfers the high accuracy of Pseudolabel to the thermal depth estimation network by comparing low- and high-level pixels. Furthermore, we propose Patch-NetVLAD Loss, which strengthens local detail and global context information in the depth map from thermal infrared imaging by comparing locally global patch-level descriptors. Finally, we introduce an Image Matching Loss to estimate a more accurate depth map in a thermal depth network by enhancing the performance of the Pseudolabel. We demonstrate that the proposed framework shows significant performance improvement even when applied to various depth networks in the KAIST Multispectral Dataset. [ABSTRACT FROM AUTHOR]

Local feature patterns are conspicuous and are widely used in computer vision, especially in face recognition and retrieval. However, a statistical descriptor that can be used in various scenarios and effectively present the detailed local discrimination information of face images is a challenging and exploring task even if deep learning technology is widelyspread. In this study, we propose a novel local pattern descriptor called the Local Clustering Pattern (LCP) in high-order derivative space for facial recognition and retrieval. Unlike prior methods, LCP exploits the concept of clustering to analyze the relationship of intra- and inter-classes of the referenced pixel and its adjacent pixels to encode the local descriptor for facial recognition. There are three tasks (1) Local Clustering Pattern (LCP), (2) Clustering Coding Scheme, (3) High-order Local Clustering Pattern. To generate local clustering pattern, the local derivative variations with multi-direction are considered and that are integrated on rectangular coordinate system with the pairwise combinatorial direction. Moreover, to generate the discriminative local pattern, the features of local derivative variations are transformed from the rectangular coordinate system into the polar coordinate system to generate the characteristics of magnitude (m) and orientation (θ ). Then, we shift and project the features (m and θ ), which are scattered in the four quadrants of polar coordinate system, into the first quadrant of polar coordinates to strengthen the relationship of intra- and inter-classes of the referenced pixel and its adjacent pixels. To encode the local pattern, we consider the spatial relationship between reference and its adjacent pixels and fuse the clustering algorithm into the coding scheme by utilizing the relationship of intra- and inter-classes in a local patch. In addition, we extend the LCP from low- into high-order derivative space to extract the detailed and abundant information for facial description. LCP efficiently encodes the feature of a local region that is discriminative the inter-classes and robust the intra-class of the related pixels to describe a face image. This study has three main contributions: (1) we generate the novel features with magnitude (m) and orientation (θ ) based on the pairs of the derivative variations to describe the characteristics of each pixel, (2) we shift and project the features from four quadrants of polar coordinate system into the first quadrant of polar coordinates to strengthen the relationship of intra- and inter-classes between pixels in a local patch, (3) we exploit the concept of clustering, which considers the relationship of intra- and inter-classes of the referenced pixel and its adjacent pixels, to encode the local descriptor in a polar coordinate system for facial recognition and retrieval. Experimental results show that LCP outperforms the existing descriptors (LBP, ELBP LDP, LTrP, LVP, LDZP, LGHP) on six public datasets (ORL, Extend Yale B, CAS PEAL, and LFW, CMU-PIE and FERET) for both face recognition and retrieval tasks. Moreover, we further compare the proposed facial descriptor with the popular deep convolutional neural networks to demonstrate the discrimination of the extracted features and applicability of our approach. [ABSTRACT FROM AUTHOR]

Many of the research problems in robot vision involve the detection of keypoints, areas with salient information in the input images and the generation of local descriptors, that encode relevant information for such keypoints. Computer vision solutions have recently relied on Deep Learning techniques, which make extensive use of the computational capabilities available. In autonomous robots, these capabilities are usually limited and, consequently, images cannot be processed adequately. For this reason, some robot vision tasks still benefit from a more classic approach based on keypoint detectors and local descriptors. In 2D images, the use of binary representations for visual tasks has shown that, with lower computational requirements, they can obtain a performance comparable to classic real-value techniques. However, these achievements have not been fully translated to 3D images, where research is mainly focused on real-value approaches. Thus, in this paper, we propose a keypoint detector and local descriptor based on 3D binary patterns. The experimentation demonstrates that our proposal is competitive against state-of-the-art techniques, while its processing can be performed more efficiently. [ABSTRACT FROM AUTHOR]

In this paper, a novel face recognition approach based on strings of successive values (SSV) is presented. In contrast to most of the existing local descriptors which encode only a limited number of pixels included in a mask, the strings extract more discriminative information over the whole face region, by moving from the current pixel to the next one, and to the other next, and so on, according to the variations of their intensities. Therefore, the SSV can be stopped in any place of the face area, which allows us to encode more edge information and texture information than the existing methods. The proposed face recognition scheme requires several steps. Firstly, the images are divided into non-overlapping sub-regions from which the strings are extracted since each pixel produces two different strings. Thereafter, the dictionary of visual words is created to reduce the number of strings obtained from each patch of the image. Therefore, the face image is described only by visual words, because each string is replaced by its nearest dictionary word. As a result, the occurrence of visual words is computed in a histogram as a face descriptor. Finally, the recognition is performed by using the nearest neighbor classifier with the Hellinger distance. The effectiveness of the proposed approach is evaluated on three different databases, and the experimental results show that the recognition performances achieved are competitive or even outperform the literature state of the art methods. [ABSTRACT FROM AUTHOR]

In this paper, a novel face recognition approach based on strings of successive values (SSV) is presented. In contrast to most of the existing local descriptors which encode only a limited number of pixels included in a mask, the strings extract more discriminative information over the whole face region, by moving from the current pixel to the next one, and to the other next, and so on, according to the variations of their intensities. Therefore, the SSV can be stopped in any place of the face area, which allows us to encode more edge information and texture information than the existing methods. The proposed face recognition scheme requires several steps. Firstly, the images are divided into non-overlapping sub-regions from which the strings are extracted since each pixel produces two different strings. Thereafter, the dictionary of visual words is created to reduce the number of strings obtained from each patch of the image. Therefore, the face image is described only by visual words, because each string is replaced by its nearest dictionary word. As a result, the occurrence of visual words is computed in a histogram as a face descriptor. Finally, the recognition is performed by using the nearest neighbor classifier with the Hellinger distance. The effectiveness of the proposed approach is evaluated on three different databases, and the experimental results show that the recognition performances achieved are competitive or even outperform the literature state of the art methods. [ABSTRACT FROM AUTHOR]

In this work, we propose a new set of H ∞ deconvolution filtering of 2-D color image using feature extraction of local descriptor and Fornasini-Machesini II (FM-II) model. The principal goal is to design 2-D deconvolution filter to reconstruct the noisy color image with the minimal information extracted from local Krawtchouk moment, Moreover, the filtering error system is asymptotically stable and satisfy the H ∞ performance index. the sufficient condition is given to ensure the H ∞ performance of the filtering error system through the Lyapunov theory, and the local Krawtckouk moment to give the feature extraction according to the order defined in advance instead of the global color image. Moreover, the 2-D deconvolution filter is designed to achieve the H ∞ performance index which the filter parameters are determined with certain optimization resolution. Finally, simulation example is provided to demonstrate the usefulness of the proposed design methods. [ABSTRACT FROM AUTHOR]

To investigate the structure-dependent peptide mobility behavior in ion mobility spectrometry (IMS), quantitative structure-spectrum relationship (QSSR) is systematically modeled and predicted for the collision cross section Ω values of totally 162 single-protonated tripeptide fragments extracted from the Bacillus subtilis lipase A. Two different types of structure characterization methods, namely, local and global descriptor as well as three machine learning methods, namely, partial least squares (PLS), support vector machine (SVM) and Gaussian process (GP), are employed to parameterize and correlate the structures and Ω values of these peptide samples. In this procedure, the local descriptor is derived from the principal component analysis (PCA) of 516 physicochemical properties for 20 standard amino acids, which can be used to sequentially characterize the three amino acid residues composing a tripeptide. The global descriptor is calculated using CODESSA method, which can generate > 200 statistically significant variables to characterize the whole molecular structure of a tripeptide. The obtained QSSR models are evaluated rigorously via tenfold cross-validation and Monte Carlo cross-validation (MCCV). A comprehensive comparison is performed on the resulting statistics arising from the systematic combination of different descriptor types and machine learning methods. It is revealed that the local descriptor-based QSSR models have a better fitting ability and predictive power, but worse interpretability, than those based on the global descriptor. In addition, since the QSSR modeling using local descriptor does not consider the three-dimensional conformation of tripeptide samples, the method would be largely efficient as compared to the global descriptor. [ABSTRACT FROM AUTHOR]

Protein–protein interactions (PPIs) help to elucidate the molecular mechanisms of life activities and have a certain role in promoting disease treatment and new drug development. With the advent of the proteomics era, some PPIs prediction methods have emerged. However, the performances of these PPIs prediction methods still need to be optimized and improved. In order to optimize the performance of the PPIs prediction methods, we used the dropout method to reduce over-fitting by deep neural networks (DNNs), and combined with three types of feature extraction methods, conjoint triad (CT), auto covariance (AC) and local descriptor (LD), to build DNN models based on amino acid sequences. The results showed that the accuracy of the CT, AC and LD increased from 97.11% to 98.12%, 96.84% to 98.17%, and 95.30% to 95.60%, respectively. The loss values of the CT, AC and LD decreased from 27.47% to 14.96%, 65.91% to 17.82% and 36.23% to 15.34%, respectively. Experimental results show that dropout can optimize the performances of the DNN models. The results can provide a resource for scholars in future studies involving the prediction of PPIs. The experimental code is available at https://github.com/smalltalkman/hppi-tensorflow. [ABSTRACT FROM AUTHOR]

This paper proposes a novel high-performance dynamic inverse distance weighting based local descriptor (DIDWLD) for facial recognition. Studies proposed thus far have focused on finding local descriptors that can represent the texture of the face best. However, the robustness of the descriptors against rotational variances and noise affects have been largely omitted. Thus, this study does not only concern with proposing a high-discriminative descriptor, but also a robust one against rotational changes and noise affects. DIDWLD mainly basis on Inverse Distance Weighting (IDW). That is, for each pixel in the image, a new descriptive value is calculated, taking into account the intensity values of the neighboring pixels and their distance to the reference pixels. A dynamic distance-decay parameter is applied throughout the image rather than keeping it uniform as done in ordinary IDW. The calculated descriptor is independent of the changes in the rotation. Because, when calculating the descriptor, the intensity values of the surrounding pixels with their distances to the reference pixel are taken into consideration, yet their directional relation to the reference pixel is ignored. Furthermore, when a pixel is suffered to noise, inherently, its neighboring pixels are also affected. Hence, by taking into account the effect of the surrounding pixels and also the original intensity value of the pixel, the degrading impact of noise on recognition performance is mitigated. The results of extensive simulations show the remarkable and competitive performance of the proposed method regarding recognition accuracy, and robustness against rotational variances and, noise effects. [ABSTRACT FROM AUTHOR]

In the last decades, iris features have been widely used in biometric systems. Because iris features are virtually unique for each person, their usage is highly reliable. However, biometric systems based on iris features are not completely fraud-resistant, as most systems use static images and do not distinguish between a live iris and a photograph. The iris structure and texture change with light variations, and traditional techniques for iris recognition always identify the iris texture in a controlled environment. However, in uncontrolled environments, live irises are recognized by their dynamic response to light: If the light changes, the pupils dilate or contract, and their texture dynamically changes. If a biometric system can identify people during the constriction or dilation time interval, that system will be more fraud-resistant. This paper proposes a new methodology to evaluate the "dynamic texture" from iris image sequences (motion analysis) and measure the discriminant power of these features for biometric system applications. We propose two new dynamic descriptors—dynamic local mapped pattern and dynamic sampled local mapped pattern—which are extensions of the local mapped pattern previously published for texture classification. We applied our proposed dynamic texture descriptors in a sequence of iris images segmented from video under light variation. Then, we compared our results with the well-known dynamic texture descriptor local binary pattern from three orthogonal planes (LBP-TOP). We used statistical measures to evaluate the performance of both descriptors and concluded that our methodology performed better than the LBP-TOP. Moreover, our descriptors can extract dynamic textures faster than the LBP-TOP. [ABSTRACT FROM AUTHOR]

In this paper, we revisit the problem of visual tracking by introducing a novel low-dimensional descriptor based on gradient distribution and specifically focus our attention on the problem of low-resolution and long-term visual tracking. We show that our tracking solution empowered by our proposed descriptor can effectively address the existing challenges in low-resolution and long-term visual tracking. Compared to the existing descriptors, the proposed method provides better robustness against local geometric and photometric variations. It adopts a new approach for aggregating information in a local neighborhood such that the sensitivity of the descriptor to noise and unreliable texture information is reduced. Integrating the proposed descriptor into a correlation-based tracking framework results in a robust and fast visual tracker. An extensive set of experiments on a number of large-scale benchmark datasets shows that the proposed method outperforms the state-of-the-art methods on low-resolution and long-term challenges, while achieving state-of-the-art performance in generic tracking. [ABSTRACT FROM AUTHOR]

Face recognition is still a very demanding area of research. This problem becomes more challenging in unconstrained environment and in the presence of several variations like pose, illumination, expression, etc. Local descriptors are widely used for this task. The most of the existing local descriptors consider only few immediate local neighbors and not able to utilize the wider local information to make the descriptor more discriminative. The wider local information based descriptors mainly suffer due to the increased dimensionality. In this paper, this problem is solved by encoding the relationship among directional neighbors in an efficient manner. The relationship between the center pixel and the encoded directional neighbors is utilized further to form the proposed local directional relation pattern (LDRP). The descriptor is inherently uniform illumination invariant. The multi-scale mechanism is also adapted to further boost the discriminative ability of the descriptor. The proposed descriptor is evaluated under the image retrieval framework over face databases. Very challenging databases like PaSC, LFW, PubFig, ESSEX, FERET, AT&T, and FaceScrub are used to test the discriminative ability and robustness of LDRP descriptor. Results are also compared with the recent state-of-the-art face descriptors such as LBP, LTP, LDP, LDN, LVP, DCP, LDGP and LGHP. Very promising performance is observed using the proposed descriptor over very appealing face databases as compared to the existing face descriptors. The proposed LDRP descriptor also outperforms the pre-trained ImageNet CNN models over large-scale FaceScrub face dataset. Moreover, it also outperforms the deep learning based DLib face descriptor in many scenarios. [ABSTRACT FROM AUTHOR]

A few light stimuli coherently distributed in the space and time are the essential input that a visual system needs to perceive motion. Inspired in such fact, a compact motion descriptor is herein proposed to describe patterns of neighboring trajectories for human action recognition. The proposed method introduces a strategy that models the local distribution of neighboring points by defining a spatial point process around motion trajectories. Particularly, a two-level occurrence analysis is carried out to discover motion patterns that underlying on trajectory points representation. Firstly, local occurrence words are computed over a circular grid layout that is centered in a fixed position for each trajectory. Then, a regional occurrence description is achieved by representing actions as the most frequent local words that occur in a particular video. This second occurrence layer could be computed for the entire video or by each frame to achieve an online recognition. This compact descriptor, with local size of 72 and sequence descriptor size of 400, acquires importance in real-time applications and environments with hardware restrictions. The proposed strategy was evaluated on KTH and Weizmann dataset, achieving an average accuracy of 91.2 and 78%, respectively. Moreover, a further online recognition was performed over UT-Interaction achieving an accuracy of 67% by using only the first 25% of video sequences. [ABSTRACT FROM AUTHOR]

The local descriptors have been the backbone of most of the computer vision problems. Most of the existing local descriptors are generated over the raw input images. In order to increase the discriminative power of the local descriptors, some researchers converted the raw image into multiple images with the help of some high and low pass frequency filters, then the local descriptors are computed over each filtered image and finally concatenated into a single descriptor. By doing so, these approaches do not utilize the inter frequency relationship which causes the less improvement in the discriminative power of the descriptor that could be achieved. In this paper, this problem is solved by utilizing the decoder concept of multi-channel decoded local binary pattern over the multi-frequency patterns. A frequency decoded local binary pattern (FDLBP) is proposed with two decoders. Each decoder works with one low frequency pattern and two high frequency patterns. Finally, the descriptors from both decoders are concatenated to form the single descriptor. The face retrieval experiments are conducted over four benchmarks and challenging databases such as PaSC, LFW, PubFig, and ESSEX. The experimental results confirm the superiority of the FDLBP descriptor as compared to the state-of-the-art descriptors such as LBP, SOBEL_LBP, BoF_LBP, SVD_S_LBP, mdLBP, etc. [ABSTRACT FROM AUTHOR]

This paper proposes a novel high-performance gradient-based local descriptor that handles the prominent challenges of face recognition such as resistance against rotational, illuminative changes as well as noise effects. One of the novelties this study poses is that, while processing the gradient for each direction, an analysis is done by considering the predecessors of the corresponding pixel as well as the successors at that direction. Furthermore, earlier studies represent these local relationships by encoding them in binary because they consider only the positive and negative intensity changes. However, we propose an alternative way of representation that encodes the relationships between each pixel and its neighbors in a multi-valued logic manner called Directional Local Gradient Based Descriptor (DLGBD). Our method not only considers the variations but also uniformity. A threshold value is defined to identify whether an intensity variation is present in the specified direction. If the intensity change exceeds the threshold value, then it is evaluated as a variation either in positively or negatively depending on the direction of the change. Three states of the relationship between multiple pixels at each direction yield a more discriminative descriptor for face retrieval. Ternary logic is applied to express three states. Ternary values that are calculated at each direction are concatenated and the resulting compound ternary value is replaced with the reference pixel. By this way, a more discriminative face descriptor is achieved which is resistant to noise and challenges in unconstrained environments. Extensive simulations are conducted over benchmark datasets and the performance of DLGBD is compared to the other state-of-the-art methods. As presented by the simulation results, the DLGBD achieves very high discriminating performance as well as providing resistance against rotation and illumination variations. [ABSTRACT FROM AUTHOR]

Copyright of Electrotechnical Review / Elektrotehniski Vestnik is the property of Electrotechnical Society of Slovenia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a novel approach for acoustic scene classification based on efficient acoustic feature extraction using spectro-temporal descriptors fusion. Grounded on the finding in neuroscience—"auditory system summarizes the temporal details of sounds using time-averaged statistics to understand acoustic scenes", we devise an efficient computational framework for sound scene classification by using multipe time-frequency descriptors fusion with discriminant information enhancement. To characterize rich information of sound, i.e., local structures on the time-frequency plane, we adopt 2-dimensional local descriptors. A more critical issue raised in how to logically 'summarize' those local details into a compact feature vector for scene classification. Although 'time-averaged statistics' is suggested by the psychological investigation, directly computing time average of local acoustic features is not a logical way, since arithmetic mean is vulnerable to extreme values which are anticipated to be generated by interference sounds which are irrelevant to the scene category. To tackle this problem, we develop time-frame weighting approach to enhance sound textures as well as to suppress scene-irrelevant events. Subsequently, robust acoustic feature for scene classification can be efficiently characterized. The proposed method had been validated by using Rouen dataset which consists of 19 acoustic scene categories with 3029 real samples. Extensive results demonstrated the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Feature extraction is a key problem in face recognition systems. This paper tackles this problem by combining the strength of image descriptor with dimensionality reduction technology. So, this paper proposes a new efficient face recognition method-local descriptor margin projections (LDMP). Firstly, we propose a novel local descriptor for face image representation. At this step, an effective and simple metric approach named gray value accumulating distance (GAD) is firstly proposed. And then a novel local descriptor based on GAD is presented to capture the local structure information between central pixel and its neighbors effectively. Secondly, we propose a dimensionality reduction algorithm named maximum margin learning projections (MMLP) which can obtain the low-dimensional and discriminative feature. Finally, experimental results on the Yale, Extended Yale B, PIE, AR and LFW face databases show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Designing effective local descriptors is crucial for many computer vision tasks such as image matching and patch verification. We propose a convolutional neural network (CNN)-based local descriptor named DHNet with a considerate sampling strategy and a dedicated loss function. By considerate sampling, both the closest nonmatching sample and the farther matching sample can be obtained for effectively training a discriminative model. In addition, an improved triplet loss is designed by adding a constraint that limits the absolute distance for the closest nonmatching pair. Based on hard samples and the constraint, our lightweight CNN can quickly generate local descriptors with enhanced intraclass compactness and interclass separation. Experimental results show that our method significantly outperforms the state-of-the-art methods in terms of strong discrimination ability, as evidenced by a considerable performance improvement on several benchmarks. ©2018 SPIE and IS&T [DOI: 10.1117/1.JEI.27.4.043008] [ABSTRACT FROM AUTHOR]

In this paper, we propose a local descriptors approach to classify pornographic images. Two local descriptors including the scale-invariant feature transform (SIFT) and the histogram of oriented gradients (HOG) are computed feature vectors from pornographic images. The extracted features are supplied to the K-Nearest Neighbor Algorithm and Support Vector Machine for pornographic image classification. We have evaluated all different methods on the TI-UNRAM dataset. The results show that the HOG and the SIFT combined with the SVM significantly outperform the other methods, including KNN algorithm and image processing technique. Thus, the local descriptors approach can be combined with the SVM for pornographic image classification in order to obtain the effective classification performance. [ABSTRACT FROM AUTHOR]

Histogram is commonly used in the area of designing features. However, most existing histogram-based descriptors ignore the information of the distribution of points in each bin. Motivated by VLAD, we introduce the locally aggregation strategy into the design of hand-crafted features to address this issue, and put forward several locally aggregated histogram-based descriptors, including LA-HOG, LA-HOF and LA-MBH, based on HOG, HOF and MBH, respectively. In the binning process of the proposed descriptors, we accumulate the differences between the local information and their nearest bin centers, which describes the distribution of the local information in each bin. The proposed descriptors are utilized in object and action recognition tasks, which are demonstrated to be complementary to the original descriptors in the experiments. The comparison results show that their combinations outperform the original descriptors alone by about 2% on average both in these two tasks. [ABSTRACT FROM AUTHOR]

With the development of image vision technology, local descriptors have attracted wide attention in the fields of image retrieval and classification. Even though varieties of methods based on local descriptor have achieved excellent performance, most of them cannot effectively represent the trend of pixels change, and they neglect the mutual occurrence of patterns. Therefore, how to construct local descriptors is of vital importance but challenging. In order to solve this problem, this paper proposes a multi-trend binary code descriptor (MTBCD). MTBCD mimics the visual perception of human to describe images by constructing a set of multi-trend descriptors which are encoded with binary codes. The method exploits the trend of pixels change in four symmetric directions to obtain the texture feature, and extracts the spatial correlation information using co-occurrence matrix. These intermediate features are integrated into one histogram using a new fusion strategy. The proposed method not only captures the global color features, but also reflects the local texture information. Extensive experiments have demonstrated the excellent performance of the proposed method. [ABSTRACT FROM AUTHOR]

The DAISY descriptor has been widely used in dense stereo matching and scene reconstruction. However, DAISY is vulnerable to similar feature regions because the construction method of DAISY sequentially arranges the description of center and neighbor sample points and does not consider their relationships. To enhance the discriminative power of the local descriptor and accelerate the speed of dense matching and scene reconstruction, we propose a low-dimensional local descriptor. The proposed descriptor is inspired from the local binary pattern (LBP). In image space, LBP describes local detail texture by computing the difference between center and neighbor sample points. We introduce this advantage in scale space to extend the DAISY descriptor and make it more efficient for dense matching similar features in the different regions. On this basis, a two-dimensional discrete cosine transform (2D-DCT) is utilized to reduce the dimensions of the descriptor as well as reduce the computation cost of dense matching and scene reconstruction. Through a variety of experiments on the benchmark laser-scanned ground truth scenes as well as indoor and outdoor scenes, we show the proposed descriptor can get more accurate depth maps and more complete reconstruction results than that of using other common descriptors, and the computational speed is much faster than that of using DAISY. [ABSTRACT FROM AUTHOR]

Local feature descriptor has been widely used in computer vision field due to their excellent discriminative power and strong robustness. However, the forms of such local descriptors are predefined in the hand-crafted way, which requires strong domain knowledge to design them. In this paper, we propose a simple and efficient Spherical Hashing based Binary Codes (SHBC) feature learning method to learn a discriminative and robust binary face descriptor in the data-driven way. Firstly, we extract patch-wise pixel difference vectors (PDVs) by computing the difference between center patch and its neighboring patches. Then, inspired by the fact that hypersphere provide much stronger power in defining a tighter closed region in the original data space than hyperplane, we learn a hypersphere-based hashing function to map these PDVs into low-dimensional binary codes by an efficient iterative optimization process, which achieves both balanced bits partitioning of data points and independence between hashing functions. In order to better capture the semantic information of the dataset, our SHBC also can be used with supervised data embedding method, such as Canonical Correlation Analysis (CCA), namely Supervised-SHBC (S-SHBC). Lastly, we cluster and pool these learned binary codes into a histogram-based feature that describes the co-occurrence of binary codes. And we consider the histogram-based feature as our final feature representation for each face image. We investigate the performance of our SHBC and S-SHBC on FERET, CAS-PEAL-R1, LFW and PaSC databases. Extensive experimental results demonstrate that our SHBC descriptor outperforms other state-of-the-art face descriptors. [ABSTRACT FROM AUTHOR]

In order to improve face recognition rate using geometric and neighborhood information, a local descriptor is proposed in this paper for 3D face recognition. In this method, equal geodesic contour line of the face is extracted and re-sampled and a local descriptor that does not rely on coordinate information is extracted by the analysis of cloud distribution information of local points on the contour line. Local characteristics are weighted and rules are integrated between the corresponding points of the tested face and library set face and ultimate recognition result is obtained by using nearest neighbor classifier. Performance of the algorithm is verified in FRGV v2.0 and experimental results show the method has good recognition performance. Improvement measures are also proposed to solve the problem that the geodesic contour line is easily affected by expression in the bottom part area of human face and experimental results show the improvement method is effective. [ABSTRACT FROM AUTHOR]

Time series classification (TSC) arises in many fields and has a wide range of applications. Here, we adopt the bag-of-words (BoW) framework to classify time series. Our algorithm first samples local subsequences from time series at feature-point locations when available. It then builds local descriptors, and models their distribution by Gaussian mixture models (GMM), and at last it computes a Fisher Vector (FV) to encode each time series. The encoded FV representations of time series are readily used by existing classifiers, e.g., SVM, for training and prediction. In our work, we focus on detecting better feature points and crafting better local representations, while using existing techniques to learn codebook and encode time series. Specifically, we develop an efficient and effective peak and valley detection algorithm from real-case time series data. Subsequences are sampled from these peaks and valleys, instead of sampled randomly or uniformly as was done previously. Then, two local descriptors, Histogram of Oriented Gradients (HOG-1D) and Dynamic time warping-Multidimensional scaling (DTW-MDS), are designed to represent sampled subsequences. Both descriptors complement each other, and their fused representation is shown to be more descriptive than individual ones. We test our approach extensively on 43 UCR time series datasets, and obtain significantly improved classification accuracies over existing approaches, including NNDTW and shapelet transform. [ABSTRACT FROM PUBLISHER]

This paper proposes a local descriptor called quaternionic local ranking binary pattern (QLRBP) for color images. Different from traditional descriptors that are extracted from each color channel separately or from vector representations, QLRBP works on the quaternionic representation (QR) of the color image that encodes a color pixel using a quaternion. QLRBP is able to handle all color channels directly in the quaternionic domain and include their relations simultaneously. Applying a Clifford translation to QR of the color image, QLRBP uses a reference quaternion to rank QRs of two color pixels, and performs a local binary coding on the phase of the transformed result to generate local descriptors of the color image. Experiments demonstrate that the QLRBP outperforms several state-of-the-art methods. [ABSTRACT FROM PUBLISHER]

This paper presents a monotonic invariant intensity descriptor (MIID) via spectral embedding and nonsubsampled contourlet transform (NSCT). To make the proposed descriptor discriminative, NSCT is used for the construction of multiple support regions. Specifically, the directed graph and the spectral feature vectors of the signless Laplacian matrix are exploited to construct the MIID. We theoretically demonstrate that the proposed descriptor is able to tackle monotonic illumination changes and many other geometric and photometric transformations. We conduct extensive experiments on the standard Oxford dataset and the complex illumination dataset to demonstrate the superiority of proposed descriptor over the existing state-of-the-art descriptors in dealing with image blur, viewpoint changes, illumination changes, and JPEG compression. [ABSTRACT FROM AUTHOR]

Sparse coding methods have achieved great success in visual tracking, and we present a strong classifier and structural local sparse descriptors for robust visual tracking. Since the summary features considering the sparse codes are sensitive to occlusion and other interfering factors, we extract local sparse descriptors from a fraction of all patches by performing a pooling operation. The collection of local sparse descriptors is combined into a boosting-based strong classifier for robust visual tracking using a discriminative appearance model. Furthermore, a structural reconstruction error based weight computation method is proposed to adjust the classification score of each candidate for more precise tracking results. To handle appearance changes during tracking, we present an occlusion-aware template update scheme. Comprehensive experimental comparisons with the state-of-the-art algorithms demonstrated the better performance of the proposed method. [ABSTRACT FROM PUBLISHER]

The local descriptors based on a binary pattern feature have state-of-the-art distinctiveness. However, their high dimensionality resists them from matching faster and being used in a low-end device. In this paper we propose an efficient and feasible learning method to select discriminative binary patterns for constructing a compact local descriptor. In the selection, a searching tree with Branch&Bound is used instead of the exhaustive enumeration, in order to avoid tremendous computation in training. New local descriptors are constructed based on the selected patterns. The efficiency of selecting binary patterns has been confirmed by the evaluation of these new local descriptors' performance in experiments of image matching and object recognition. [ABSTRACT FROM AUTHOR]

Highly discriminant visual features play a key role in different image classification applications. This study aims to realize a method for extracting highly-discriminant features from images by exploring a robust local descriptor inspired by Weber’s law. The investigated local descriptor is based on the fact that human perception for distinguishing a pattern depends not only on the absolute intensity of the stimulus but also on the relative variance of the stimulus. Therefore, we firstly transform the original stimulus (the images in our study) into a differential excitation-domain according to Weber’s law, and then explore a local patch, called micro-Texton, in the transformed domain as Weber local descriptor (WLD). Furthermore, we propose to employ a parametric probability process to model the Weber local descriptors, and extract the higher-order statistics to the model parameters for image representation. The proposed strategy can adaptively characterize the WLD space using generative probability model, and then learn the parameters for better fitting the training space, which would lead to more discriminant representation for images. In order to validate the efficiency of the proposed strategy, we apply three different image classification applications including texture, food images and HEp-2 cell pattern recognition, which validates that our proposed strategy has advantages over the state-of-the-art approaches. [ABSTRACT FROM PUBLISHER]

The emergence of an RGB-D (Red-Green-Blue-Depth) sensor which is capable of providing depth and RGB images gives hope to the computer vision community. Moreover, the use of local features began to increase over the last few years and has shown impressive results, especially in the field of object recognition. This article attempts to provide a survey of the recent technical achievements in this area of research. We review the use of local descriptors as the feature representation which is extracted from RGB-D images, in instances and category-level object recognition. We also highlight the involvement of depth images and how they can be combined with RGB images in constructing a local descriptor. Three different approaches are used in involving depth images into compact feature representation, that is classical approach using distribution based, kernel-trick, and feature learning. In this article, we show that the involvement of depth data successfully improves the accuracy of object recognition. [ABSTRACT FROM AUTHOR]

We propose a new method to analyse the similarity of protein CPK models. In the proposed method we first construct the skeleton of protein models by an improvedL1-medial skeleton extraction. The skeleton information is then used to form a local radius descriptor. Finally, the shape similarity of protein models is compared by using the local radius descriptor based on the absolute degree of grey incidence. Experimental results show that the improvedL1-medial skeleton of protein models can describe the shapes of the protein models well. The local descriptor based on the skeleton combined with the absolute degree of grey incidence shows satisfactory performance for comparing the shape similarity of protein CPK models. [ABSTRACT FROM AUTHOR]

Local feature descriptor is a fundamental representation for image patch which has been extensively used in many computer vision applications. In this paper, different from state-of-the-art features, a novel biologically inspired local descriptor (BILD) is proposed based on the visual information processing mechanism of ventral pathway in human brain. The local features used for constructing BILD are extracted by a two-layer network, which corresponds to the simple-to-complex cell hierarchy in the primary visual cortex (V1). It works in a similar way as the simple cell and complex cell do to get responses by applying the lateral inhibition from different orientations and operating an improved cortical pooling. To enhance the distinctiveness of BILD, we combine the local features from different orientations. Extensive evaluations have been performed for image matching and object recognition. Experimental results reveal that our proposed BILD outperforms many widely used descriptors such as SIFT and SURF, which demonstrate its efficiency for representing local regions. [ABSTRACT FROM AUTHOR]