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Learning from large-scale contrastive language-image pre-training like CLIP has shown remarkable success in a wide range of downstream tasks recently, but it is still under-explored on the challenging few-shot action recognition (FSAR) task. In this work, we aim to transfer the powerful multimodal knowledge of CLIP to alleviate the inaccurate prototype estimation issue due to data scarcity, which is a critical problem in low-shot regimes. To this end, we present a CLIP-guided prototype modulating framework called CLIP-FSAR, which consists of two key components: a video-text contrastive objective and a prototype modulation. Specifically, the former bridges the task discrepancy between CLIP and the few-shot video task by contrasting videos and corresponding class text descriptions. The latter leverages the transferable textual concepts from CLIP to adaptively refine visual prototypes with a temporal Transformer. By this means, CLIP-FSAR can take full advantage of the rich semantic priors in CLIP to obtain reliable prototypes and achieve accurate few-shot classification. Extensive experiments on five commonly used benchmarks demonstrate the effectiveness of our proposed method, and CLIP-FSAR significantly outperforms existing state-of-the-art methods under various settings. The source code and models are publicly available at https://github.com/alibaba-mmai-research/CLIP-FSAR. [ABSTRACT FROM AUTHOR]

Existing retinex-based low-light image enhancement strategies focus heavily on crafting complex networks for Retinex decomposition but often result in imprecise estimations. To overcome the limitations of previous methods, we introduce a straightforward yet effective strategy for Retinex decomposition, dividing images into colormaps and graymaps as new estimations for reflectance and illumination maps. The enhancement of these maps is separately conducted using a diffusion model for improved restoration. Furthermore, we address the dual challenge of perturbation removal and brightness adjustment in illumination maps by incorporating brightness guidance. This guidance aids in precisely adjusting the brightness while eliminating disturbances, ensuring a more effective enhancement process. Extensive quantitative and qualitative experimental analyses demonstrate that our proposed method improves the performance by approximately 4.4 % on the LOL dataset compared to other state-of-the-art diffusion-based methods, while also validating the model's generalizability across multiple real-world datasets. [ABSTRACT FROM AUTHOR]

Since the fully convolutional network has achieved great success in semantic segmentation, lots of works have been proposed to extract discriminative pixel representations. However, the authors observe that existing methods still suffer from two typical challenges: (i) The intra‐class feature variation between different scenes may be large, leading to the difficulty in maintaining the consistency between same‐class pixels from different scenes; (ii) The inter‐class feature distinction in the same scene could be small, resulting in the limited performance to distinguish different classes in each scene. The authors first rethink semantic segmentation from a perspective of similarity between pixels and class centers. Each weight vector of the segmentation head represents its corresponding semantic class in the whole dataset, which can be regarded as the embedding of the class center. Thus, the pixel‐wise classification amounts to computing similarity in the final feature space between pixels and the class centers. Under this novel view, the authors propose a Class Center Similarity (CCS) layer to address the above‐mentioned challenges by generating adaptive class centers conditioned on each scenes and supervising the similarities between class centers. The CCS layer utilises the Adaptive Class Center Module to generate class centers conditioned on each scene, which adapt the large intra‐class variation between different scenes. Specially designed Class Distance Loss (CD Loss) is introduced to control both inter‐class and intra‐class distances based on the predicted center‐to‐center and pixel‐to‐center similarity. Finally, the CCS layer outputs the processed pixel‐to‐center similarity as the segmentation prediction. Extensive experiments demonstrate that our model performs favourably against the state‐of‐the‐art methods. [ABSTRACT FROM AUTHOR]

Visual Question Answering (VQA) is a multimodal task, which requires understanding the information in the natural language questions and paying attention to the useful information in the images. So far, the solution of VQA tasks can be divided into grid-based methods and bottom-up-based methods. The grid-based method directly extracts the semantic features of the image by leveraging the convolution neural network (CNN), so it has a praiseworthy computational efficiency, but the global convolution feature ignores the information of the key area and causes the performance bottleneck. The bottom-up-based method needs to detect potentially problem-related objects by using some object detection frameworks, e.g. Faster RCNN, so it has better performance, but the computational efficiency is reduced due to the computation of Region Proposal Network (RPN) and Non-Maximum Suppression (NMS). Based on the aforementioned reasons, we propose a fully transformer-based network (FTN) that can maintain a balance between computational efficiency and accuracy, which can be trained end-to-end and consists of three components: question module, image module, and fusion module. Meanwhile, the image module and the question module are visualized to explore the operating rules of the transformer. The experiment results demonstrate that the FTN can focus on key information and objects in the question module and the image module, and our single model has reached 69.01% accuracy on the VQA2.0 dataset, which is superior to the grid-based methods. Although FTN fails to surpass a few state-of-the-art bottom-up-based methods, the FTN has obvious advantages in computational efficiency. The code will be released at https://github.com/weixiang-xu/FTN-VQA.git. [ABSTRACT FROM AUTHOR]

Image stylization has attracted considerable attention from various fields. Although impressive results have been achieved, existing methods pay less attention to the preservation of outline and putting constraint on it when training, which makes generated images suffering from different degrees of distortion. To address this issue, we propose a dual attention mechanism based outline loss to enhance the restriction of outline consistency by incorporating an outline detection module and a dual attention module. Specifically, an outline detection module is used to detect outlines of the source image and the stylized image, which are further compared and enforced to be consistent with each other by a carefully-elaborated outline loss. Additionally, the dual attention module first guides the model to focus on regions of the source image whose style has the biggest difference from the target image during stylization based on the style attention feature map obtained by the auxiliary classifier. Then, an outline attention map is predicted to highlight regions where the outlines are prone to distort during stylization, which further facilitates the outline loss to execute stronger constraint on these regions. Experimental results show the superiority of our method compared to the existing state-of-the-art methods [ABSTRACT FROM AUTHOR]

Recently, crowd counting via estimating a density map has been widely studied. However, it still has a variety of issues to overcome, such as large-scale variation of population, complex background noise, perspective distortion, etc. The large-scale variation of heads will restrict the performance of crowd counting approaches, and the complex background noise will result in the background, such as leaf and mesh, being incorrectly recognized as heads. To maintain large-scale variation and generate a high-quality estimated density map, we propose a novel multi-scale fusion scale-aware attention network called multi-scale and gated spatial attention network (MGSNet). In MGSNet, the first 10 layers of VGG16 with Batch Normalization (BN) are utilized as backbone. Then, two branches, i.e., a large-scale branch and a scale–aware attention branch, are followed. The large-scale branch is used to overcome the large-scale variation of heads in crowd images, in which a Scale Information Aggregation Block (SIAB) is employed to extract multi-scale features by utilizing dilated convolution with different receptive fields. The scale-aware attention branch is used to address complex background noise in crowd scenes, in which a Gated Spatial Attention Block (GSAB) inspired by the Long Short-term Memory Networks (LSTM) is employed to fuse the previous information with different scales and retain the appropriate scale information of crowds. We demonstrate our proposed method on the ShanghaiTech (Part AB), UCF-CC-50 and UCF-QNRF datasets. The experimental results show its effectiveness over the state-of-the-art. [ABSTRACT FROM AUTHOR]

In this work, we present a new method for 3D face reconstruction from sparse‐view RGB images. Unlike previous methods which are built upon 3D morphable models (3DMMs) with limited details, we leverage an implicit representation to encode rich geometric features. Our overall pipeline consists of two major components, including a geometry network, which learns a deformable neural signed distance function (SDF) as the 3D face representation, and a rendering network, which learns to render on‐surface points of the neural SDF to match the input images via self‐supervised optimization. To handle in‐the‐wild sparse‐view input of the same target with different expressions at test time, we propose residual latent code to effectively expand the shape space of the learned implicit face representation as well as a novel view‐switch loss to enforce consistency among different views. Our experimental results on several benchmark datasets demonstrate that our approach outperforms alternative baselines and achieves superior face reconstruction results compared to state‐of‐the‐art methods. [ABSTRACT FROM AUTHOR]

The deep learning based methods have improved the visual tracking precision significantly. However, the background distraction and the high precise localization remain challenging problems. Despite that some methods have fused the deep and shallow layer features to solve these problems, the existing fusion methods, like simply concatenating or adding the features from the different layers, cannot take the advantage of both the deep and shallow layer features fully. In this paper, we propose a new adaptive feature fusion method, called the instance-based feature pyramid (IBFP) to obtain the discriminative high-resolution feature, which not only inherits the discriminative information from the deep layer feature, but also keeps the high precision localization information of the shallow layer feature. For utilizing the deep and shallow features effectively, we design an instance-based upsampling (IBU) module to fuse them, and a compressed space channel selection (CSCS) module to re-weight the feature channels adaptively. We insert the IBU and CSCS modules in the Siamese tracker for end-to-end training and testing. By using the proposed IBU and CSCS modules, we fuse the deep and shallow features in a series manner. Experiments on large-scale benchmark datasets demonstrate that the proposed modules boost the capabilities of distinguishing the targets and the similar distractors and perform favorably against the state-of-the-art. [ABSTRACT FROM AUTHOR]

Margin-based metric losses have shown great success in Person Re-identification and Face Verification. But most existing works adopt a fixed class-level margin regardless of the difference between each training sample. This paper proposes a Norm-Aware Margin Assignment (NAMA) scheme to dynamically adjust the weight of each sample during training. Combined with the existing margin-based classification losses, NAMA improves the robustness of feature embedding by assigning larger margins to more recognizable samples. NAMA is a fully trainable module that automatically models the correlation between the optimal margin and image quality during back-propagation without supervision. To stabilize the training and make the assigned margin more controllable, we introduce a margin re-balance mechanism to align the expectation of learned margins to a pre-defined value. Extensive experiments on three popular ReID benchmarks validate the effectiveness of our NAMA method. Code will be publicly available at: https://github.com/huangzongheng/NAMA. [ABSTRACT FROM AUTHOR]

In this article, we propose a novel compressed latent distribution representation for 3D hand pose estimation from monocular RGB images to alleviate the channel correspondence problem. The channel correspondence problem occurs when the 2D and depth coordinates are estimated from independent feature maps, which means the 2D and depth channel sequences may not match during the cross-dataset inference. In contrast, we propose a compressed latent distribution representation that the 2D and depth feature maps for each joint are interconnected and inter-constrained more directly, effectively alleviating the channel correspondence problem and improving cross-dataset performance. Moreover, we design an efficient encoder-decoder network that can maintain the resolution of feature maps to enable better hand feature extraction from monocular RGB images. In this work, the overall pipeline contains two branches: one is the 2D hand pose estimation branch based on a latent heatmap representation (LHR); the other is the 3D hand pose estimation branch based on our proposed latent distribution representation (LDR). In this way, the 2D estimation branch serves as guidance for the 3D branch, which simplifies the optimization of the overall network and results in a more rapid convergence during training. The results on several benchmark datasets (including STB, RHD, and the most recently released InterHand2.6M) demonstrate that our proposed method achieves state-of-the-art (SOTA) performance. [ABSTRACT FROM AUTHOR]

Low-level details and high-level semantics are both essential to the semantic segmentation task. However, to speed up the model inference, current approaches almost always sacrifice the low-level details, leading to a considerable decrease in accuracy. We propose to treat these spatial details and categorical semantics separately to achieve high accuracy and high efficiency for real-time semantic segmentation. For this purpose, we propose an efficient and effective architecture with a good trade-off between speed and accuracy, termed Bilateral Segmentation Network (BiSeNet V2). This architecture involves the following: (i) A detail branch, with wide channels and shallow layers to capture low-level details and generate high-resolution feature representation; (ii) A semantics branch, with narrow channels and deep layers to obtain high-level semantic context. The detail branch has wide channel dimensions and shallow layers, while the semantics branch has narrow channel dimensions and deep layers. Due to the reduction in the channel capacity and the use of a fast-downsampling strategy, the semantics branch is lightweight and can be implemented by any efficient model. We design a guided aggregation layer to enhance mutual connections and fuse both types of feature representation. Moreover, a booster training strategy is designed to improve the segmentation performance without any extra inference cost. Extensive quantitative and qualitative evaluations demonstrate that the proposed architecture shows favorable performance compared to several state-of-the-art real-time semantic segmentation approaches. Specifically, for a 2048 × 1024 input, we achieve 72.6% Mean IoU on the Cityscapes test set with a speed of 156 FPS on one NVIDIA GeForce GTX 1080 Ti card, which is significantly faster than existing methods, yet we achieve better segmentation accuracy. The code and trained models are available online at https://git.io/BiSeNet. [ABSTRACT FROM AUTHOR]

Fine-grained information has been proved helpful for person re-identification, and multi-head attention mechanism offers a feasible solution for this. However, we observe severe redundancy among the multiple branches, which might make the learned representation over-emphasize certain discriminative regions and correspondingly ignore other potentially informative regions. Therefore, we tackle this issue by two aspects yielding the so-called Complementation-Reinforced Attention Network (CRAN). One is the redundancy among branches, and we propose to impose complementing constraints among multiple attention heads. The constraints are two-fold: on the one hand, it encourages each branch to attend to complementary attention regions; on the other hand, it enforces orthogonality among the learned features of different regions in the embedding space. The other is the redundancy among query positions for each attention head. So we simplify the attention block by sparsifying the query positions. Besides, in order to achieve efficient retrieval, we propose an adaptive feature fusion method for dimensional reduction. Compared with the commonly used feature ensemble, our method effectively reduces the dimensionality while keeping the discriminative ability. We demonstrate the effectiveness of our method on MSMT17, Market-1501, DukeMTMC-reID, and CUHK03 datasets. [ABSTRACT FROM AUTHOR]

Stripe and random noise are two different degradation phenomena that commonly coexist in optical remote sensing images, and they are often modeled as inverse problems. In model-based inverse problems, analysis and synthesis sparse representations (SSRs) are used as regularization terms to obtain approximate solutions due to their respective merits, i.e., the nonzero coefficients in SSR are usually used to describe an image, while the indexes of zeros in analysis sparse representation (ASR) are used to characterize the stripe. Inspired by these merits, we propose a unified variational framework, called a joint analysis and weighted synthesis (JAWS) sparsity model, to simultaneously separate the clean image and the stripe from a single optical remote sensing image. To solve the JAWS sparsity model efficiently, an alternating minimization optimization strategy is first employed to separate it into two subproblems that are used for different tasks. One called as weighted SSR (WSSR) is the main for optical remote sensing image denoising, which can be effectively solved by employing the weighted singular value thresholding operator, while the other called as ASR is the main approach for optical remote sensing image destriping, which is optimized by adopting the split Bregman iteration. By minimizing the two subproblems alternatively, the proposed JAWS sparsity model is efficiently solved. Finally, both quantitative and qualitative results of experiments on synthetic and real-world optical remote sensing images validate that the proposed approach is effective and even better than the state of the arts. [ABSTRACT FROM AUTHOR]

In this paper, we address the challenging problem of weakly supervised spatio-temporal action localization for which only video-level action labels are available during training. To solve this problem, we propose an end-to-end Global Local Network (GLNet) to predict the probability distribution simultaneously in both spatial and temporal space. The proposed GLNet model includes two key components: a local spatial module and a global temporal module. The local spatial module aims to predict the frame-level spatial distribution by encoding short-term temporal information. In particular, we propose a Region Actionness Network (RAN) to select the target region boxes from the precomputed exhaustive proposals. The global temporal module can predict temporal distribution by a long-term temporal structure modelling. Specifically, we design a temporal fusion-and-excitation architecture on the top of several clips, and trained by a sparse loss function. Therefore, the proposed GLNet model can perform spatio-temporal action localization in an end-to-end manner. We evaluate the performance of GLNet on the J-HMDB and UCF101-24 datasets. The experimental results demonstrate GLNet achieves a significant margin against other state-of-the-art weakly supervised methods and even some fully supervised methods in terms of frame mean Average Precision (mAP) and the video mAP (called frame-mAP and video-mAP, respectively). [ABSTRACT FROM AUTHOR]

Dynamic scene blur is usually caused by object motion, depth variation as well as camera shake. Most existing methods usually solve this problem using image segmentation or fully end-to-end trainable deep convolutional neural networks by considering different object motions or camera shakes. However, these algorithms are less effective when there exist depth variations. In this work, we propose a deep neural convolutional network that exploits the depth map for dynamic scene deblurring. Given a blurred image, we first extract the depth map and adopt a depth refinement network to restore the edges and structure in the depth map. To effectively exploit the depth map, we adopt the spatial feature transform layer to extract depth features and fuse with the image features through scaling and shifting. Our image deblurring network thus learns to restore a clear image under the guidance of the depth map. With substantial experiments and analysis, we show that the depth information is crucial to the performance of the proposed model. Finally, extensive quantitative and qualitative evaluations demonstrate that the proposed model performs favorably against the state-of-the-art dynamic scene deblurring approaches as well as conventional depth-based deblurring algorithms. [ABSTRACT FROM AUTHOR]

We present an effective semi-supervised learning algorithm for single image dehazing. The proposed algorithm applies a deep Convolutional Neural Network (CNN) containing a supervised learning branch and an unsupervised learning branch. In the supervised branch, the deep neural network is constrained by the supervised loss functions, which are mean squared, perceptual, and adversarial losses. In the unsupervised branch, we exploit the properties of clean images via sparsity of dark channel and gradient priors to constrain the network. We train the proposed network on both the synthetic data and real-world images in an end-to-end manner. Our analysis shows that the proposed semi-supervised learning algorithm is not limited to synthetic training datasets and can be generalized well to real-world images. Extensive experimental results demonstrate that the proposed algorithm performs favorably against the state-of-the-art single image dehazing algorithms on both benchmark datasets and real-world images. [ABSTRACT FROM AUTHOR]

This work develops a biologically inspired neural network for contour detection in natural images by combining the nonclassical receptive field modulation mechanism with a deep learning framework. The input image is first convolved with the local feature detectors to produce the classical receptive field responses, and then a corresponding modulatory kernel is constructed for each feature map to model the nonclassical receptive field modulation behaviors. The modulatory effects can activate a larger cortical area and thus allow cortical neurons to integrate a broader range of visual information to recognize complex cases. Additionally, to characterize spatial structures at various scales, a multiresolution technique is used to represent visual field information from fine to coarse. Different scale responses are combined to estimate the contour probability. Our method achieves state-of-the-art results among all biologically inspired contour detection models. This study provides a method for improving visual modeling of contour detection and inspires new ideas for integrating more brain cognitive mechanisms into deep neural networks. [ABSTRACT FROM AUTHOR]

Stripe and random noise are two different degradation phenomena commonly co-existing in optical remote sensing images, which are often modelled as inverse problems, respectively. When solving those inverse problems, model-based optimization and discriminative learning methods are fashionably employed but have their respective merits and drawbacks, e.g., model-based optimization methods are flexible but usually time-consuming while discriminative learning methods have fast testing speed but are limited by the specialized task. To improve testing speed and obtain good performance, this paper integrates deep convolutional neural network (DCNN) denoiser prior into unidirectional variation (UV) model, named as UV-DCNN, to simultaneously destripe and denoise optical remote sensing images. The proposed UV-DCNN method can be efficiently solved by the alternating minimization optimization method. Both quantitative and qualitative experiment results validate that the proposed method is effective and even better than the state-of-the-arts, its satisfactory computation time makes it suitable for extensive application. [ABSTRACT FROM AUTHOR]

We present an effective blind image deblurring method based on a data-driven discriminative prior. Our work is motivated by the fact that a good image prior should favor sharp images over blurred ones. In this work, we formulate the image prior as a binary classifier using a deep convolutional neural network. The learned prior is able to distinguish whether an input image is sharp or not. Embedded into the maximum a posterior framework, it helps blind deblurring in various scenarios, including natural, face, text, and low-illumination images, as well as non-uniform deblurring. However, it is difficult to optimize the deblurring method with the learned image prior as it involves a non-linear neural network. In this work, we develop an efficient numerical approach based on the half-quadratic splitting method and gradient descent algorithm to optimize the proposed model. Furthermore, we extend the proposed model to handle image dehazing. Both qualitative and quantitative experimental results show that our method performs favorably against the state-of-the-art algorithms as well as domain-specific image deblurring approaches. [ABSTRACT FROM AUTHOR]

Recently, safe semi-supervised learning has attracted more and more attention in the machine learning field. Many methods are introduced to safely exploit unlabeled data by designing different safe mechanisms. However, they assume that the risk or safety degrees are equal for all unlabeled data. In this paper, we propose an adaptive safe semi-supervised learning framework where the safety degrees of different unlabeled data are different and adaptively computed. In this framework, a safety degree-based tradeoff term between supervised learning (SL) and semi-supervised learning (SSL) is incorporated into the objective function of SSL. Then the optimal problem is solved by using an alternating iterative strategy. In particular, we utilize Regularized Least Squares (RLS) and Laplacian RLS (LapRLS) for SL and SSL, respectively. Our experimental results on several datasets demonstrate that the performance of our algorithm is never significantly inferior to that of RLS and LapRLS and show the effectiveness of our proposed safety mechanism. [ABSTRACT FROM AUTHOR]

Enhancement and denoising have always been a pair of conflicting problems in image processing of computer vision. Inspired by an earlier dual-domain filter (DDF), this letter proposes a progressive DDF to simultaneously enhance and denoise low-quality optical remote-sensing images. The main procedure of the proposed enhancement filter has two parts. First, a bilateral filter is exploited as a guide filter to obtain high-contrast images, which are enhanced by a histogram modification method. Then, low-contrast useful structures are restored by a short-time Fourier transform and are enhanced using an adaptive correction parameter. Both the quantitative and qualitative results of experiments on synthetic and real-world low-quality remote-sensing images demonstrate that the proposed method performs well on contrast enhancement, structure preservation, and noise reduction. Moreover, its satisfactory computation time resulting from its simple implementation makes it suitable for extensive application. [ABSTRACT FROM PUBLISHER]

Semantic parts have shown a powerful discriminative capacity for action recognition. However, many existing methods select parts according to predefined heuristic rules, which may cause the correlation among parts to be lost, or do not appropriately consider the cluttered candidate part space, which may result in weak generalizability of the resulting action labels. Therefore, better consideration of the correlation among parts and refinement of the candidate space will lead to a more discriminative action representation. This paper achieves improved performance by more elegantly addressing these two factors. First, considering the cluttered nature of the candidate space, we propose a recursive part elimination strategy for iterative refinement of the candidate parts. In each iteration, we eliminate the parts with the lowest weights, which are deemed to be noise. Second, we measure the discriminative capabilities of the candidates and select the top-ranked parts by applying a maximum margin model, which can alleviate overfitting while simultaneously improving generalizability and correlation extraction. Finally, using the selected parts, we extract mid-level features. We report experiments conducted on four datasets (KTH, Olympic Sports, UCF50, and HMDB51). The proposed method can achieve significant improvements compared with other recent methods, including a lower computational cost, a faster speed, and higher accuracy. [ABSTRACT FROM PUBLISHER]

Non‐local self‐similar patch‐based denoising techniques have been viewed as the most popular denoising approaches in computer vision. This study has proposed a novel iterative weighted sparse representation (IWSR) scheme for X‐ray cardiovascular angiogram image denoising. The main procedures of this scheme include four parts. First, a maximum a posterior (MAP) distribution by the Bayes' theory is adopted to simultaneously estimate the estimated image and sparse representation with different Gaussian distributions approximating to likelihood prior, non‐local self‐similar patch prior and sparse representation prior. Second, the MAP problem is converted to minimise an energy function using the logarithmic transformation. Third, the function is efficiently solved by the single and effective alternating directions method of multipliers algorithm along with singular value decomposition (SVD) algorithm. Finally, owing to learned dictionary by K‐SVD algorithm, the qualitative and quantitative results of widely synthetic experiments demonstrate that the proposed IWSR denoising method performs effectively and can obtain competitive denoising performance and high‐quality images compared with those advanced denoising methods. The results of extensive experiments on clinical X‐ray angiogram images further illustrate that the IWSR method performs well on noise reduction and vascular structures including edges and capillaries preservation, integral cardiovascular trees of which are beneficial for clinicians to diagnose and analyse cardiovascular diseases. [ABSTRACT FROM AUTHOR]

Low-rank regularization approximated by a nuclear norm has been proven its ability in image denoising. However, the nuclear norm is just a suboptimization of the rank norm, resulting in a big error when reducing noise. In this paper, a novel smooth and convex surrogate function, which is closer to the rank norm, is firstly proposed as a replacement of the prior nuclear norm. Then, the proposed surrogate function is approximated by its first-order Taylor expansion. Finally, a novel model called iterative weighted nuclear norm minimization scheme, solved by the single and effective alternating directions method of multipliers with a weighted singular-value thresholding operator, is formed for image denoising. Both quantitative and qualitative results obtained by applying advanced denoising methods to synthetic images will verify the effectiveness of the proposed method. Extensive application of these state-of-the-art methods to denoising of clinical X-ray cardiovascular angiograms further validates that our proposed approach performs better on reducing noise and preserving structures (especially capillaries), demonstrating that the method can yield clear X-ray angiograms with integral cardiovascular trees which are beneficial for clinicians to diagnose and analyze cardiovascular diseases. [ABSTRACT FROM AUTHOR]

It is important to track people's face efficiently and accurately in many Intelligent Transportation Systems (ITSs) and Safety Driving Assistant Systems (SDASs). This paper presents a high-performance and low-cost real-time face tracking system, which runs on general onboard computer with very low CPU consumption. The proposed face tracking system is composed of four modules: the motion detector, face detector, face tracker, and face validator. The motion detector extracts motion areas by using a spatial-temporal bi-differential method with a very low computational cost. The face detector integrates motions into a cascade face detection framework to reject most of non-face scanning-windows to ensure efficient face localization. The face tracker fuses motion feature with color feature to alleviate the drifting problem during tracking. The face validator builds face appearance models online and identifies each specific tracked face to avoid confusion. Experimental results on three challenging video sequences show that the proposed face tracking system outperforms the state-of-the-art face tracker and consumes only 5-13% CPU resources of a low-spec onboard computer while processing in real time. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The classification of hyperspectral image with a paucity of labeled samples is a challenging task. In this paper, we present a discriminant sparse representation (DSR) graph for semi-supervised learning (SSL) to address this problem. For graph-based methods, how to construct a graph among the pixels is the key to a successful classification. Our graph construction method contains two steps. Sparse representation (SR) method is first employed to estimate the probability matrix of the pairwise pixels belonging to the same class, and then this probability matrix is integrated into the SR graph, which can be obtained by solving an ℓ optimization problem, to form a DSR graph. Experiments on Hyperion and AVIRIS hyperspectral data show that our proposed method outperforms state of the art. [ABSTRACT FROM AUTHOR]

Mid-level parts are shown to be effective for human action recognition in videos. Typically, these semantic parts are first mined with some heuristic rules, then videos are represented via volumetric max-pooling (VMP) method. However, these methods have two issues: 1) the VMP strategy divides videos by static grids. In this case, a semantic part may occur in different localizations in different videos. That means the VMP strategy loses the space-time invariance. To solve this problem, we propose to apply a saliency-driven max-pooling scheme to represent a video. We extract the video semantic cues by the saliency map, and dynamically pool the local maximum responses. This scheme can be considered as a semantic content-based feature alignment method and 2) the parts discovered by heuristic rules may be intuitive but not discriminative enough for action classification because they neglect the relations between the detectors. For this issue, we propose to apply a sparse classifier model to select discriminative parts. Moreover, to further improve the discriminative ability of the representation, we propose to conduct feature selection by the corresponding entry magnitude of the model coefficients. We conduct experiments on four challenging datasets—KTH, Olympic Sports, UCF50, and HMDB51. The results show that the proposed method significantly outperforms the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Person reidentification (re-id) aims to match a specific person across nonoverlapping cameras, which is an important but challenging task in video surveillance. Conventional methods mainly focus either on feature constructing or metric learning. Recently, some deep learning-based methods have been proposed to learn image features and similarity measures jointly. However, current deep models for person re-id are usually trained with either pairwise loss, where the number of negative pairs greatly outnumbering that of positive pairs may lead the training model to be biased toward negative pairs or constant margin hinge loss, without considering the fact that hard negative samples should be paid more attention in the training stage. In this paper, we propose to learn deep representations with an adaptive margin listwise loss. First, ranking lists instead of image pairs are used as training samples, in this way, the problem of data imbalance is relaxed. Second, by introducing an adaptive margin parameter in the listwise loss function, it can assign larger margins to harder negative samples, which can be interpreted as an implementation of the automatic hard negative mining strategy. To gain robustness against changes in poses and part occlusions, our architecture combines four convolutional neural networks, each of which embeds images from different scales or different body parts. The final combined model performs much better than each single model. The experimental results show that our approach achieves very promising results on the challenging CUHK03, CUHK01, and VIPeR data sets. [ABSTRACT FROM PUBLISHER]

Tracking by detection has become an attractive tracking technique, which treats tracking as an object detection problem and trains a detector to separate the target object from the background in each frame. While this strategy is effective to some extent, we argue that the task in tracking should be searching for a specific object instance instead of an object category. Based on this viewpoint, a novel framework based on object exemplar detectors is proposed for visual tracking. To build a specific and discriminative model to separate the object instance from the background, the proposed method trains an exemplar-based linear discriminant analysis (ELDA) classifier for the object exemplar, using the current tracked instance as the positive sample and massive negative samples obtained both offline and online. To improve the trackers’ adaptivity, we use an ensemble of the above ELDA detectors and update them during the tracking to cover the variation in object appearance. Extensive experimental results on a large benchmark data set show that the proposed method outperforms many state-of-the-art trackers, demonstrating the effectiveness and robustness of the ELDA tracker. [ABSTRACT FROM AUTHOR]

This paper presents a novel tracking-by-detection approach for multitarget tracking. There are two major steps in our framework: data association to form global tracklet association, followed by trajectory estimation to deal with the remaining gaps. In the first step, we formulate tracklet association as an inference problem in a Hough forest random field, which combines Hough forest and conditional random field and allows us to model both local and global tracklet relationships in one unified model. In the second step, we improve the reversible-jump Markov chain Monte Carlo particle filtering method with explicit mutual-occlusion reasoning to fill in the remaining gaps from the first step and increase the overall tracking precision. Extensive experiments have been conducted on five public data sets, and the performance is comparable to that of the state-of-the-art method, if not better. [ABSTRACT FROM AUTHOR]

This letter presents a novel multi-target tracking approach consisting of two parts. The first part is the detection based association to form global tracks. Short yet reliable tracklets are firstly generated. By effectively combining appearance and motion information, a Hough forest learning framework is constructed to obtain a more discriminative affinity model and produce longer association between tracklets. In the second part, in order to connect isolate detections for trajectory consistency, we present an appearance similarity model based on mutual occlusion reasoning. A novel fusion feature template is designed to accurately compute the matching score between each isolated detection and target. Experimental results show significant improvements of our method when compared with several state-of-the-art methods. [ABSTRACT FROM PUBLISHER]

This paper addresses the remote sensing image fusion problem from the perspective of the analysis sparse model. As an alternative to the synthesis sparse representation approach, the analysis sparse model can yield richer feature representations and better results for image restoration. We, therefore, propose an image fusion method for remote sensing images based on the analysis sparse model. In this method, the analysis operators for the high-resolution multispectral (HR MS) image are trained band by band, directly from the source images, which can greatly improve the adaptability. During the analysis operator learning stage, the geometric analysis operator learning (GOAL) algorithm is utilized with the upsampled low-resolution MS (LR MS) image and the HR panchromatic (HR PAN) image, which does not require an external HR MS image data set. Moreover, the imagery system modulation transfer function (MTF) is considered during the LR MS imaging modeling process, which greatly extends the practical application potential of the proposed method. The simulated and real-data experimental results on IKONOS and QuickBird data sets show that the proposed method can effectively preserve the spectral information and the spatial detail of the image. The fused HR MS images produced by the proposed method are comparable and even superior to the images fused by the other state-of-the-art methods. [ABSTRACT FROM PUBLISHER]

Person re-identification is the task of finding a person of interest across a network of cameras. In this paper, we propose a new similarity learning method for person re-identification. Conventional metric learning methods generally learn a linear transformation by employing sparse pairwise or triplet constraints. Since a lot of negative matching pairs or triplets are abandoned, the discriminative information is not fully exploited. Similarity learning methods with AUC loss can utilize all valid triplet constraints. However, the AUC loss has its own limitation by treating all false ranks occured at different positions equally. To address this limitation, we propose to extend the AUC loss to the top-heavy ranking loss by assigning large weights to top positions of the ranking list. Moreover, we introduce an explicit nonlinear transformation function for the original feature space and learn an inner product similarity under the structured output learning framework. Our approach achieves very promising results on the challenging VIPeR, CUHK Campus and PRID 450S datasets. [ABSTRACT FROM PUBLISHER]