Digital watermarking algorithm based on scale-invariant feature regions in non-subsampled contourlet transform domain

Contraposing the need of the robust digital watermark for the copyright protection field, a new digital watermarking algorithm in the non-subsampled contourlet transform （NSCT） domain is proposed. The largest energy sub-band after NSCT is selected to embed watermark. The watermark is embedded into scaleinvariant feature transform （SIFT） regions. During embedding, the initial region is divided into some cirque sub-regions with the same area, and each watermark bit is embedded into one sub-region. Extensive simulation results and comparisons show that the algorithm gets a good trade-off of invisibility, robustness and capacity, thus obtaining good quality of the image while being able to effectively resist common image processing, and geometric and combo attacks, and normalized similarity is almost all reached.

Spectral matching algorithm based on nonsubsampled contourlet transform and scale-invariant feature transform

A new spectral matching algorithm is proposed by us- ing nonsubsampled contourlet transform and scale-invariant fea- ture transform. The nonsubsampled contourlet transform is used to decompose an image into a low frequency image and several high frequency images, and the scale-invariant feature transform is employed to extract feature points from the low frequency im- age. A proximity matrix is constructed for the feature points of two related images. By singular value decomposition of the proximity matrix, a matching matrix （or matching result） reflecting the match- ing degree among feature points is obtained. Experimental results indicate that the proposed algorithm can reduce time complexity and possess a higher accuracy.

Mosaic of the Curved Human Retinal Images Based on the Scale-Invariant Feature Transform

To meet the needs in the fundus examination,including outlook widening,pathology tracking,etc.,this paper describes a robust feature-based method for fully-automatic mosaic of the curved human retinal images photographed by a fundus microscope. The kernel of this new algorithm is the scale-,rotation-and illumination-invariant interest point detector & feature descriptor-Scale-Invariant Feature Transform. When matched interest points according to second-nearest-neighbor strategy,the parameters of the model are estimated using the correct matches of the interest points,extracted by a new inlier identification scheme based on Sampson distance from putative sets. In order to preserve image features,bilinear warping and multi-band blending techniques are used to create panoramic retinal images. Experiments show that the proposed method works well with rejection error in 0.3 pixels,even for those cases where the retinal images without discernable vascular structure in contrast to the state-of-the-art algorithms.

Keypoint全功能肌电诱发电位故障维修1例

Keypoint全功能肌电诱发电位是维迪公司的一款性能稳定可靠、使用便捷的台式肌电图,在使用中轻轻点击快速完成数据采集即可将患者从痛苦的检查中解放出来。Keypoint具有保留所有原始的波形提供给医师在报告时阅读分析参考诊断。

Spatial continuity and stress transfer:Primary and complementary factors shaping pure-swarm laboratory catalog into mixed burst-like and swarm-like

Natural earthquakes and micro-seismicity resulting from hydraulic fracturing or other engineering practices display distinctively different spatial-temporal features,like mixed burst-and swarm-like features or predominantly swarm-like features.The mechanism(s)contributing to such observations can be diverse.We present the inspections on the dynamic formation process of the single swarm-like tree in laboratory acoustic emission(AE)catalogs.Such largest swarm-like trees can contain>97%AE events from the entire catalog within a test;and all catalogs under investigation display scale-invariance features.The formation of the largest swarm-like tree correlates with the rock fracture process analogue of the source pervasive process,where its AE releases exhibit significant spatial well-organization.Comparison to other laboratory catalogs under different laboratory settings helps us identify the spatial continuity of the rock fracture process as the primary factor in forming the largest swarm-like trees at laboratory scale.The stress transfer process is involved in the rock fracture process for the tests having pre-existing spatial discontinuity.Artificial perturbations on the spatial information induced by the stress transfer process further confirm that stress transfer also serves to shift the pure swarm-like catalog into a mixed burst-and swarm-like catalog.These laboratory observations may provide inspirational insights for understanding the field-scale mechanism(s)shaping the spatial-temporal energy release features.

基于Keypoint RCNN改进模型的物体抓取检测算法

机器人抓取在工业中的应用有两个难点:如何准确地检测可抓取物体,以及如何从检测出的多个物体中选择最优抓取目标。本文在Keypoint RCNN模型中引入同方差不确定性学习各损失的权重,并在特征提取器中加入注意力模块,构成了Keypoint RCNN改进模型。基于改进模型提出了两阶段物体抓取检测算法,第一阶段用模型预测物体掩码和关键点,第二阶段用掩码和关键点计算物体的抓取描述和重合度,重合度表示抓取时的碰撞程度,根据重合度可以从多个可抓取物体中选择最优抓取目标。对照实验证明,相较原模型,Keypoint RCNN改进模型在目标检测、实例分割、关键点检测上的性能均有提高,在自建数据集上的平均精度分别为85.15%、79.66%、86.63%,机器人抓取实验证明抓取检测算法能够准确计算物体的抓取描述、选择最优抓取,引导机器人无碰撞地抓取目标。

Copy-Move Forgeries Detection and Localization Using Two Levels of Keypoints Extraction

Copy-move offense is considerably used to conceal or hide several data in the digital image for specific aim, and onto this offense some portion of the genuine image is reduplicated and pasted in the same image. Therefore, Copy-Move forgery is a very significant problem and active research area to check the confirmation of the image. In this paper, a system for Copy Move Forgery detection is proposed. The proposed system is composed of two stages: one is called the detection stages and the second is called the refine detection stage. The detection stage is executed using Speeded-Up Robust Feature (SURF) and Binary Robust Invariant Scalable Keypoints (BRISK) for feature detection and in the refine detection stage, image registration using non-linear transformation is used to enhance detection efficiency. Initially, the genuine image is picked, and then both SURF and BRISK feature extractions are used in parallel to detect the interest keypoints. This gives an appropriate number of interest points and gives the assurance for finding the majority of the manipulated regions. RANSAC is employed to find the superior group of matches to differentiate the manipulated parts. Then, non-linear transformation between the best-matched sets from both extraction features is used as an optimization to get the best-matched set and detect the copied regions. A number of numerical experiments performed using many benchmark datasets such as, the CASIA v2.0, MICC-220, MICC-F600 and MICC-F2000 datasets. With the proposed algorithm, an overall average detection accuracy of 95.33% is obtained for evaluation carried out with the aforementioned databases. Forgery detection achieved True Positive Rate of 97.4% for tampered images with object translation, different degree of rotation and enlargement. Thus, results from different datasets have been set, proving that the proposed algorithm can individuate the altered areas, with high reliability and dealing with multiple cloning.

Keypoint Description Using Statistical Descriptor with Similarity-Invariant Regions

This article presents a method for the description of key points using simple statistics for regions controlled by neighboring key points to remedy the gap in existing descriptors.Usually,the existent descriptors such as speeded up robust features(SURF),Kaze,binary robust invariant scalable keypoints(BRISK),features from accelerated segment test(FAST),and oriented FAST and rotated BRIEF(ORB)can competently detect,describe,and match images in the presence of some artifacts such as blur,compression,and illumination.However,the performance and reliability of these descriptors decrease for some imaging variations such as point of view,zoom(scale),and rotation.The intro-duced description method improves image matching in the event of such distor-tions.It utilizes a contourlet-based detector to detect the strongest key points within a specified window size.The selected key points and their neighbors con-trol the size and orientation of the surrounding regions,which are mapped on rec-tangular shapes using polar transformation.The resulting rectangular matrices are subjected to two-directional statistical operations that involve calculating the mean and standard deviation.Consequently,the descriptor obtained is invariant(translation,rotation,and scale)because of the two methods;the extraction of the region and the polar transformation techniques used in this paper.The descrip-tion method introduced in this article is tested against well-established and well-known descriptors,such as SURF,Kaze,BRISK,FAST,and ORB,techniques using the standard OXFORD dataset.The presented methodology demonstrated its ability to improve the match between distorted images compared to other descriptors in the literature.

Two-Fold and Symmetric Repeatability Rates for Comparing Keypoint Detectors

The repeatability rate is an important measure for evaluating and comparing the performance of keypoint detectors.Several repeatability rate measurementswere used in the literature to assess the effectiveness of keypoint detectors.While these repeatability rates are calculated for pairs of images,the general assumption is that the reference image is often known and unchanging compared to other images in the same dataset.So,these rates are asymmetrical as they require calculations in only one direction.In addition,the image domain in which these computations take place substantially affects their values.The presented scatter diagram plots illustrate how these directional repeatability rates vary in relation to the size of the neighboring region in each pair of images.Therefore,both directional repeatability rates for the same image pair must be included when comparing different keypoint detectors.This paper,firstly,examines several commonly utilized repeatability rate measures for keypoint detector evaluations.The researcher then suggests computing a two-fold repeatability rate to assess keypoint detector performance on similar scene images.Next,the symmetric mean repeatability rate metric is computed using the given two-fold repeatability rates.Finally,these measurements are validated using well-known keypoint detectors on different image groups with various geometric and photometric attributes.

Multi-Level Feature Aggregation-Based Joint Keypoint Detection and Description

Image keypoint detection and description is a popular method to find pixel-level connections between images,which is a basic and critical step in many computer vision tasks.The existing methods are far from optimal in terms of keypoint positioning accuracy and generation of robust and discriminative descriptors.This paper proposes a new end-to-end selfsupervised training deep learning network.The network uses a backbone feature encoder to extract multi-level feature maps,then performs joint image keypoint detection and description in a forward pass.On the one hand,in order to enhance the localization accuracy of keypoints and restore the local shape structure,the detector detects keypoints on feature maps of the same resolution as the original image.On the other hand,in order to enhance the ability to percept local shape details,the network utilizes multi-level features to generate robust feature descriptors with rich local shape information.A detailed comparison with traditional feature-based methods Scale Invariant Feature Transform(SIFT),Speeded Up Robust Features(SURF)and deep learning methods on HPatches proves the effectiveness and robustness of the method proposed in this paper.

Clothes Keypoints Detection with Cascaded Pyramid Network

With the development of the society,people's requirements for clothing matching are constantly increasing when developing clothing recommendation system.This requires that the algorithm for understanding the clothing images should be sufficiently efficient and robust.Therefore,we detect the keypoints in clothing accurately to capture the details of clothing images.Since the joint points of the garment are similar to those of the human body,this paper utilizes a kind of deep neural network called cascaded pyramid network(CPN)about estimating the posture of human body to solve the problem of keypoints detection in clothing.In this paper,we first introduce the structure and characteristic of this neural network when detecting keypoints.Then we evaluate the results of the experiments and verify effectiveness of detecting keypoints of clothing with CPN,with normalized error about 5%7%.Finally,we analyze the influence of different backbones when detecting keypoints in this network.

Skeleton Keypoints Extraction Method Combined with Object Detection

Big data is a comprehensive result of the development of the Internet of Things and information systems.Computer vision requires a lot of data as the basis for research.Because skeleton data can adapt well to dynamic environment and complex background,it is used in action recognition tasks.In recent years,skeleton-based action recognition has received more and more attention in the field of computer vision.Therefore,the keypoints of human skeletons are essential for describing the pose estimation of human and predicting the action recognition of the human.This paper proposes a skeleton point extraction method combined with object detection,which can focus on the extraction of skeleton keypoints.After a large number of experiments,our model can be combined with object detection for skeleton points extraction,and the detection efficiency is improved.

基于深度学习的二维人体姿态估计研究进展

人体姿态估计在人体行为识别、人机交互、体育运动分析等方面有着广泛的应用前景,是计算机视觉领域的一个研究热点。在最近的十年中,得益于深度学习技术,大量的研究工作极大地推动了人体姿态估计技术的发展,但由于受训练样本不足、人体姿态的多变性、遮挡、环境的复杂性等因素影响,人体姿态估计仍然面临着诸多的挑战。文中对近年来基于深度学习的2D人体姿态估计方法进行归纳和总结,着重分析一些有代表性的人体姿态估计方法的思路及工作原理,以便研究人员了解当前的研究现状、面临的挑战以及今后的研究方向,拓展研究思路。

一种具有尺度不变性的人体姿态估计算法

针对现有的人体姿态估计算法无法准确检测小尺寸、大尺寸人体关键点和精确度较低的问题,提出一种具有尺度不变性的卷积神经网络用于估计人体姿态。首先设计图像缩放网络将输入图像缩放到标准尺寸。该网络能够抑制由插值引起的特征丢失。其次引入非局部卷积,增加网络的感受野。再次为多分辨率特征融合引入分辨率注意力机制,提高网络的尺度不变性。最后设计优化网络,抑制由采样引起的量化误差。在COCO数据集进行实验的结果表明,所提算法的平均精度均值达到79.2%高于其他算法,因此所提算法的尺度不变性和准确度优于现有人体姿态估计算法。

多关键点约束与深度估计辅助的单目3D目标检测算法

当前主流的单目相机3D目标检测网络采用关键点检测范式,存在关键点预测与深度估计不准确的问题,限制了单目3D检测器的性能表现.本文提出一种多关键点约束与深度估计辅助的单目3D目标检测算法Mono-Aux,利用3D检测框的角点投影点、上表面与下表面中心投影点作为3D框中心投影点的补充,通过多关键点约束提升关键点预测精度;提出一种LiDAR-Free解耦深度估计方法,在不引入激光点云数据的同时通过几何关系推导引入额外的深度估计辅助监督信号,提升深度估计的准确性.多关键点约束与深度估计辅助仅在训练阶段使用,推理阶段不引入额外的计算成本.在KITTI3D目标检测验证集和测试集上的结果显示,相较于MonoDLE基线网络,提出的MonoAux算法在目标检测精度上分别提高3.87%和4.64%,与其他SOTA方法相比,本文方法也具有显著的性能优势,甚至优于部分使用额外数据的方法.

面向人体姿态图像关键点检测的深度学习算法

传统人体姿态检测方法提取图像信息能力弱,易受背景环境干扰,在图像辨识上具有一定的局限性。为解决由于背景干扰而导致的人体姿态识别准确率低、计算效率差的问题,提出了一种基于人体关键点骨架合成与上深度学习姿态识别算法相结合的框架体系。首先采用MobileNet残差网络优化Open Pose网络结构,降低人体骨骼关键点识别的计算复杂度,提高计算效率;然后通过PAF算法预测骨架的最优连通域,构建出最优人体骨架信息,并基于最优骨架信息生成人体骨架辅助框提取法则,提取人体姿态的相对位置,解决环干扰的问题;接着将人体关键点特征与HOG特征有机融合,基于深度学习网络构建出OP-GAN人体姿态识别模型。仿真结果表明,与传统SVM模型相比,OP-GAN模型的F1综合性能指标提升了6.85%;与其它深度学习算法相比,关键点特征的融合以及GAN网络的使用均与模型的性能指标呈正相关关系。因此,新构建的OP-GAN人体姿态识别模型通过解决背景干扰的同时,提高了人体姿态识别的准确率与效率。

基于改进沙漏的攀岩运动关键点检测算法

针对关键点检测中目标尺度多变以及不同特征适应性等难题,为进一步提升现有的姿态估计方法在实现姿态估计任务时的性能,验证单阶段和多阶段姿态估计方法各自的有效性,提出一种基于改进沙漏的攀岩运动关键点检测算法。首先设计一个多路池化残差结构,改善由于沙漏网络多次上下采样带来的信息损失和上下文信息提取不足的局限性,提升浅层特征在关键点检测中的表现;其次在沙漏网络中引入沙漏注意力结构,通过利用特征映射将输入信息划分为不同大小的特征块序列,在特征编码和特征解码两个过程中,充分挖掘图像有效信息,使得在特征匹配过程中不仅考虑本身的拟合程度,更考虑到关节位置之间的关联信息。实验表明,提出的算法在公开数据集MPII、COCO和针对攀岩运动的数据集上表现良好,且算法泛化能力较好,能够应用于多种运动场景中的人体关键点检测任务。

基于锚点的快速三维手部关键点检测算法

在人机协作任务中,手部关键点检测为机械臂提供目标点坐标,A2J(Anchor-to-Joint)是具有代表性的一种利用锚点进行关键点检测的方法。A2J以深度图为输入,可实现较好的检测效果,但对全局特征获取能力不足。文中设计了全局-局部特征融合模块(Global-Local Feature Fusion,GLFF)对骨干网络浅层和深层的特征进行融合。为了提升检测速度,文中将A2J的骨干网络替换为ShuffleNetv2并对其进行改造,用5×5深度可分离卷积替换3×3深度可分离卷积,增大感受野,有效提升了骨干网络对全局特征的提取能力。文中在锚点权重估计分支引入高效通道注意力模块(Efficient Channel Attention,ECA),提升了网络对重要锚点的关注度。在主流数据集ICVL和NYU上进行的训练和测试结果表明,相比于A2J,文中所提方法的平均误差分别降低了0.09 mm和0.15 mm。在GTX1080Ti显卡上实现了151 frame·s^(-1)的检测速率,满足人机协作任务对于实时性的要求。

描述符与特征点结合的实时激光里程计

针对同步定位与建图在低功耗嵌入式系统中无法满足实时定位建图的问题,提出了一种描述符与特征点结合的实时激光里程计。本文将描述符法与特征点法相结合,前端将角点特征关联改为描述符关联,该方法首先以划分扇区的方式对角点进行点云聚类生成关键点,然后根据关键点之间的向量关系生成多维描述符,通过描述符匹配降低点云帧间匹配时间和位姿优化时间,从而降低系统的运行时间,达到定位建图的实时性,后端在描述符约束生成的粗位姿基础上,对角点、面点使用帧到地图(ScanToMap)的两步列文伯格–马夸尔特法(Levenberg-Marquardt,LM)非线性优化,进一步保证建图的实时性和鲁棒性。在KITTI公开数据集中进行实验测试的结果表明,研究可为同步定位与建图在低功耗嵌入式系统中满足实时定位建图提供参考。

挥发窑鼓风管的关键点识别及其摆放位置监测

窑头鼓风管的摆放位置是影响氧化锌挥发窑燃烧状态的重要操作参数之一,现仍由人工看火来手动调节,同时现场没有为挥发窑的运行优化记录完善的鼓风状态数据,也难以及时发现鼓风管被窑内渣块击中等安全隐患.针对上述问题,本文提出一种基于关键点识别的鼓风管位置监测方法.首先,文章对从窑头看火口采集的火焰视频数据集设计一种邻域关键点辅助的数据扩充方法,并构建级联金字塔网络(CPN)来预测鼓风管管口中心点的位置;然后,本文提出一种基于多帧图像的聚类分析算法来消除因烟尘遮挡所产生的异常点,并采用一种量化指标来实现对挥发窑鼓风管摆放位置的实时感知与记录;最后,本文基于现场采集的火焰视频数据进行了对比实验,结果表明所提出的关键点检测模型精度高、鲁棒性强,且鼓风管位置的量化准确率高达92.3%.