共查询到19条相似文献,搜索用时 234 毫秒
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目的 光流估计是计算机视觉研究中的一个重要方向,尽管光流估计方法不断改进,但光照变化条件下光流计算精度的提高仍然是一个尚待解决的挑战。人脸反欺诈方法对于确保人脸识别系统的安全性十分重要,光照鲁棒的脸部运动光流特征能为人脸活体检测提供有关运动和结构的可靠信息。为了获得对含光照变化视频中物体运动的理解能力并应用于人脸活体检测,提高系统性能,提出了一种基于结构纹理感知视网膜模型的鲁棒光流估计方法。方法 基于Retinex理论,通过结构纹理感知方式将图像中的反射分量与光照分量充分解耦。由于反射分量具有丰富的纹理信息且光照分量中包含部分有用的结构信息,因此对所提取的光照分量进行滤波操作后再与反射分量一起融合到光流模型中,有效提高了光流估计的鲁棒性。为使模型所获光流具有更好的边缘保持性,采用光滑—稀疏正则化约束方式进行最小化求解。本文给出了求解优化问题的数值方法。结果 采用MPI Sintel数据集图像序列,与PWC-Net、DCFlow+KF和FDFlowNet(fast deep flownet)等主流算法进行对比实验,本文方法在Clean和Final数据集中均得到最低的平均终点误差(end-... 相似文献
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针对光照变化和大位移运动等复杂场景下图像序列变分光流计算的边缘模糊与过度分割问题,文中提出基于运动优化语义分割的变分光流计算方法.首先,根据图像局部区域的去均值归一化匹配模型,构建变分光流计算能量泛函.然后,利用去均值归一化互相关光流估计结果,获取图像运动边界信息,优化语义分割,设计运动约束语义分割的变分光流计算模型.最后,融合图像不同标签区域光流,获得光流计算结果.在Middlebury、UCF101数据库上的实验表明,文中方法的光流估计精度与鲁棒性较高,尤其对光照变化、弱纹理和大位移运动等复杂场景的边缘保护效果较优. 相似文献
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基于对偶树复小波和MRF模型的纹理图像分割 总被引:1,自引:0,他引:1
基于对偶树复小波(DT-CWT)和马尔可夫随机场(MRF)模型提出了一种监督纹理图像分割算法,算法包括两个步骤,首先对复小波变换系数进行较为精确的建模,提取其一阶统计信息作为纹理特征,综合多个尺度的信息,基于极大似然标准进行初始分割;其次,将初始分割结果用MRF模型表示,基于贝叶斯最大后验(MAP)融合初始分割结果,得到最终的分割结果。算法应用于合成纹理图像和实际图像得到了良好的结果,对比实验表明算法所采用的纹理特征的提取方法、小波变换方式、用MRF模型来建模标号等是算法简洁有效的基础。 相似文献
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Black M.J. Jepson A.D. 《IEEE transactions on pattern analysis and machine intelligence》1996,18(10):972-986
This paper presents a new model for estimating optical flow based on the motion of planar regions plus local deformations. The approach exploits brightness information to organize and constrain the interpretation of the motion by using segmented regions of piecewise smooth brightness to hypothesize planar regions in the scene. Parametric flow models are estimated in these regions in a two step process which first computes a coarse fit and then estimates the appropriate parametrization of the motion of the region. The initial fit is refined using a generalization of the standard area-based regression approaches. Since the assumption of planarity is likely to be violated, we allow local deformations from the planar assumption in the same spirit as physically-based approaches which model shape using coarse parametric models plus local deformations. This parametric plus deformation model exploits the strong constraints of parametric approaches while retaining the adaptive nature of regularization approaches. Experimental results on a variety of images model produces accurate flow estimates while the incorporation of brightness segmentation boundaries 相似文献
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For intelligent/autonomous subsea vehicles,reliable short-range horizontal positioning is difficult to achieve,particularly over flat bottom topography.A potential solution proposed in this paper utilized a passive optical sensing method to estimate the vehicle displacement using the bottom surface texture.The suggested optical flow method does not require any feature correspondences in images and it is robust in allowing brightness changes between image frames.Fundamentally,this method is similar to correlation methods attempting to match images and compute the motion disparity.However,in correlation methods,searching a neighbor region blindly for best match is lengthy.Main contributions of this paper come from the analysis showing that optical flow computation based on the general model cannot avoid errors except for null motion although the sign of optical flow keeps correct,and from the development of an iterative shifting method based on the error characteristics to accurately determine motions.Advantages of the proposed method are verified by real image experiments. 相似文献
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A segmentation method based on the integration of motion and brightness is proposed for image sequences. The method is composed of two parallel pathways that process motion and brightness, respectively, Inspired by the visual system, the motion pathway has two stages. The first stage estimates local motion at locations with reliable information. The second stage performs segmentation based on local motion estimates. In the brightness pathway, the input scene is segmented into regions based on brightness distribution. Subsequently, segmentation results from the two pathways are integrated to refine motion estimates. The final segmentation is performed in the motion network based on refined estimates. For segmentation, locally excitatory globally inhibitory oscillator network (LEGION) architecture is employed whereby the oscillators corresponding to a region of similar motion/brightness oscillate in synchrony and different regions attain different phases. Results on synthetic and real image sequences are provided, and comparisons with other methods are made. 相似文献
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Shot Change Detection Using Scene-Based Constraint 总被引:1,自引:0,他引:1
A key step for managing a large video database is to partition the video sequences into shots. Past approaches to this problem tend to confuse gradual shot changes with changes caused by smooth camera motions. This is in part due to the fact that camera motion has not been dealt with in a more fundamental way. We propose an approach that is based on a physical constraint used in optical flow analysis, namely, the total brightness of a scene point across two frames should remain constant if the change across two frames is a result of smooth camera motion. Since the brightness constraint would be violated across a shot change, the detection can be based on detecting the violation of this constraint. It is robust because it uses only the qualitative aspect of the brightness constraint—detecting a scene change rather than estimating the scene itself. Moreover, by tapping on the significant know-how in using this constraint, the algorithm's robustness is further enhanced. Experimental results are presented to demonstrate the performance of various algorithms. It was shown that our algorithm is less likely to interpret gradual camera motions as shot changes, resulting in a significantly better precision performance than most other algorithms. 相似文献
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Chin-Hung Teng Shang-Hong Lai Yung-Sheng Chen Wen-Hsing Hsu 《Computer Vision and Image Understanding》2005,97(3):315-346
In this paper, we present a very accurate algorithm for computing optical flow with non-uniform brightness variations. The proposed algorithm is based on a generalized dynamic image model (GDIM) in conjunction with a regularization framework to cope with the problem of non-uniform brightness variations. To alleviate flow constraint errors due to image aliasing and noise, we employ a reweighted least-squares method to suppress unreliable flow constraints, thus leading to robust estimation of optical flow. In addition, a dynamic smoothness adjustment scheme is proposed to efficiently suppress the smoothness constraint in the vicinity of the motion and brightness variation discontinuities, thereby preserving motion boundaries. We also employ a constraint refinement scheme, which aims at reducing the approximation errors in the first-order differential flow equation, to refine the optical flow estimation especially for large image motions. To efficiently minimize the resulting energy function for optical flow computation, we utilize an incomplete Cholesky preconditioned conjugate gradient algorithm to solve the large linear system. Experimental results on some synthetic and real image sequences show that the proposed algorithm compares favorably to most existing techniques reported in literature in terms of accuracy in optical flow computation with 100% density. 相似文献
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时变图象光流场计算技术是计算机视觉中的重要研究内容,也是当今研究的热点问题。为了使人们对该技术有一个较全面的了解,因而对时变图象光流场计算技术的研究和进展做了较系统的论述,首先分别列举了灰度时变图象和彩色时变图象的光流场计算方法,并对这些方法进行了分类,然后总结了出目前图象光流场计算中存在的几个问题,最后对光流场计算技术的研究发展及其应用前景指出了一些可能的方向。 相似文献
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Jonathan Gagnon Julin E. Guzmn Valentin Vervondel Franois Dagenais David Mould Eric Paquette 《Computer Graphics Forum》2019,38(7):491-500
We propose an approach for temporally coherent patch‐based texture synthesis on the free surface of fluids. Our approach is applied as a post‐process, using the surface and velocity field from any fluid simulator. We apply the texture from the exemplar through multiple local mesh patches fitted to the surface and mapped to the exemplar. Our patches are constructed from the fluid free surface by taking a subsection of the free surface mesh. As such, they are initially very well adapted to the fluid's surface, and can later deform according to the free surface velocity field, allowing a greater ability to represent surface motion than rigid or 2D grid‐based patches. From one frame to the next, the patch centers and surrounding patch vertices are advected according to the velocity field. We seek to maintain a Poisson disk distribution of patches, and following advection, the Poisson disk criterion determines where to add new patches and which patches should e flagged for removal. The removal considers the local number of patches: in regions containing too many patches, we accelerate the temporal removal. This reduces the number of patches while still meeting the Poisson disk criterion. Reducing areas with too many patches speeds up the computation and avoids patch‐blending artifacts. The final step of our approach creates the overall texture in an atlas where each texel is computed from the patches using a contrast‐preserving blending function. Our tests show that the approach works well on free surfaces undergoing significant deformation and topological changes. Furthermore, we show that our approach provides good results for many fluid simulation scenarios, and with many texture exemplars. We also confirm that the optical flow from the resulting texture matches the fluid velocity field. Overall, our approach compares favorably against recent work in this area. 相似文献
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针对照片与视频重放这一常见人脸识别欺诈手段,利用人脸攻击图像的语义信息提出一种基于光流与纹理特征融合的人脸活体检测算法:采集连续两帧待检测人脸图像,通过光流法及人脸检测方法生成人脸区域光流场变化图,将其与原始RGB图像输入至2通道卷积神经网络提取并融合得到人脸动-静态特征,基于融合特征实现真实人脸与欺诈人脸分类.此外,... 相似文献