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Approximate Poisson disk sampling on mesh

Science China(Information Sciences) 2013年第9期56卷 194-205页

作者： GENG Bo ZHANG HuiJuan WANG Heng WANG GuoPing Graphics and Interactive Technology Lab of Dept. of Computer Science Peking University The Key Lab of Machine perception and intelligent MOE

Poisson disk sampling has been widely used in many applications such as remeshing, procedural texturing, object distribution, illumination, etc. While 2D Poisson disk sampling is intensively studied in recent years, direct Poisson disk sampling on 2-manifold surface is rarely covered. In this paper, we present a novel framework which generates approximate Poisson disk distribution directly on mesh, a discrete representation of 2-manifold surfaces. Our framework is easy to implement and provides extra flexibility to specified sampling issues like feature-preserving sampling and adaptive sampling. We integrate the tensor voting method into feature detection and adaptive sample radius calculation. Remeshing as a special downstream application is also addressed. According to our experiment results, our framework is efficient, robust, and widely applicable.

关键词： Poisson disk sampling feature preserving sampling adaptive sampling remeshing tensor voting

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Graph Representation Learning Meets Computer Vision: A Survey

IEEE Transactions on Artificial Intelligence

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IEEE Transactions on Artificial Intelligence 2023年第1期4卷 2-22页

作者： Jiao, Licheng Chen, Jie Liu, Fang Yang, Shuyuan You, Chao Liu, Xu Li, Lingling Hou, Biao Key Lab. of Intelligent Perception and Image Understanding of the Ministry of Education of China International Research Center of Intelligent Perception and Computation School of Artificial Intelligence Xidian University Xi'an710071 China

A graph structure is a powerful mathematical abstraction, which can not only represent information about individuals but also capture the interactions between individuals for reasoning. Geometric modeling and relational inference based on graph data is a long-standing topic of interest in the computer vision community. In this article, we provide a systematic review of graph representation learning and its applications in computer vision. First, we sort out the evolution of representation learning on graphs, categorizing them into the nonneural network and neural network methods based on the way the nodes are encoded. Specifically, nonneural network methods, such as graph embedding and probabilistic graphical models, are introduced, and neural network methods, such as graph recurrent neural networks, graph convolutional networks, and variants of graph neural networks, are also presented. Then, we organize the applications of graph representation algorithms in various vision tasks (such as image classification, semantic segmentation, object detection, and tracking) for review and reference, and the typical graph construction approaches in computer vision are also summarized. Finally, on the background of biology and brain inspiration, we discuss the existing challenges and future directions of graph representation learning and computer vision. © 2022 IEEE.

关键词： Computer vision

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ViWoSG:A distributed scene graph of ultra-massive distributed virtual environments

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Science in China(Series F) 2009年第3期52卷 457-469页

作者： WANG GuoPing, LI Sheng, WANG ShaoRong, LU Bin & LI WenHang key lab.of machine perception and intelligent, MOE Department of Computer Science, Peking University, Beijing 100871, China Key Lab of Machine Perception and Intelligent MOE Beijing China Department of Computer Science Peking University Beijing 100871 China

An ultra-massive distributed virtual environment generally consists of ultra-massive terrain data and a large quantity of objects and their attribute data, such as 2D/3D geometric models, audio/video, images, vectors, characteristics, etc. In this paper, we propose a novel method for constructing distributed scene graphs with high extensibility. This method can support high concurrent interaction of clients and implement various tasks such as editing, querying, accessing and motion controlling. Some application experiments are performed to demonstrate its efficiency and soundness.

关键词： VR distributed system scene graph ultra-massive distributed scene graph

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Contour Knowledge-aware perception Learning for Semantic Segmentation

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IEEE Transactions on Circuits and Systems for Video Technology 2024年第5期35卷 4560-4575页

作者： You, Chao Jiao, Licheng Li, Lingling Liu, Xu Liu, Fang Ma, Wenping Yang, Shuyuan Xidian University Key Lab. Of Intelligent Perception And Image Understanding Of The Ministry Of Education Of China International Research Center Of Intelligent Perception And Computation School Of Artificial Intelligence Xi'an710071 China

The diversity of contextual information is of great importance for accurate semantic segmentation. However, most methods focus on single spatial contextual information, which results in an overlap of the semantic content of categories and a loss of contour information of objects. In this article, we propose a novel contour knowledge-aware perception learning network (CKPL-Net) to capture diverse contextual information by space-category aggregation module (SCAM) and contour-aware calibration module (CACM). First, SCAM is introduced to enhance intraclass consistency and interclass differentiation of features. By integrating space-aware and category-aware attention, SCAM reduces the redundancy of features from a categorical perspective while maintaining spatial correlation of pixels, substantially avoiding the overlap of the semantic content in categories. Second, CACM is designed to maintain the integrity of objects by perceiving contour contextual information. It develops a novel contour-aware knowledge and adaptively transforms the grid structure of convolutions for boundary pixels, which effectively calibrates the representation of features near boundaries. Finally, the quantitative and qualitative analyses on the three public datasets: ISPRS Potsdam dataset, ISPRS Vaihingen dataset, and WHDLD dataset, demonstrate that the proposed CKPL-Net achieves superior performance compared with prevalent methods, which indicates diverse contextual information is beneficial for accurate segmentation. © 1991-2012 IEEE.

关键词： Semantic Segmentation

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Design of M-channel linear-phase wavelet-like filter banks using FIR notch filters

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Journal of Computational Information Systems 2013年第15期9卷 6037-6046页

作者： Zhong, Wei Zhang, Qin Xie, Xuemei Shi, Guangming Peng, Bin Key Lab. of Media Audio and Video of Ministry of Education Communication University of China Beijing 100024 China Key Lab. of Intelligent Perception and Image Understanding of Ministry of Education Xidian University Xi'an 710071 China

In this paper, we propose a new design method for M-channel wavelet-like filter banks with highly desired linear-phase (LP) property. It is based on the LP near-perfect-reconstruction (NPR) filter bank designed by the efficient modulation technique, with additional regularity condition. Since the FIR notch filter has desired zeros at notch frequencies, it is employed to achieve the regularity condition in the proposed wavelet-like filter bank. By imposing those notch filters on the obtained NPR filters, the original LP NPR bank is thus converted to the LP wavelet-like filter bank without optimization procedure, leading to a less design effort. Further the LP property as well as good system performance of the original NPR filter bank can be preserved in the resulting system even with the increase of the degree of regularity. Design example shows that with the proposed method, the good system performance can be achieved in the resulting LP wavelet-like filter bank with different degrees of regularity. © 2013 Binary Information Press.

关键词： Filter banks

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SAR image despeckling based on edge detection and nonsubsampled second generation bandelets

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Journal of Systems Engineering and Electronics 2009年第3期20卷 519-526页

作者： Zhang Wenge~(1,2),Liu Fang~(1,2),Jiao Licheng~(2,3)& Gao Xinbo~(2,3) 1.School of Computer Science and Technology,Xidian Univ.,Xi’an 710071,P.R.China 2.key lab.of intelligent perception and Image Understanding of Ministry of Education of China,Xi’an 710071,P.R.China 3.Inst,of intelligent Information Processing,Xidian Univ.,Xi’an 710071,P.R.China School of Computer Science and Technology Xidian Univ. Xi'an 710071 P. R. China Key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of China Xi'an 710071 P. R. China Key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of China Xi'an 710071 P. R. China Inst. of Intelligent Information Processing Xidian Univ. Xi'an 710071 P. R. China

To preserve the sharp features and details of the synthetic aperture radar （SAR） image effectively when despeckling, a despeckling algorithm with edge detection in nonsubsampled second generation bandelet transform （NSBT） domain is proposed. First, the Canny operator is utilized to detect and remove edges from the SAR image. Then the NSBT which has an optimal approximation to the edges of images and a hard thresholding rule are used to approximate the details while despeckling the edge-removed image. Finally, the removed edges are added to the reconstructed image. As the edges axe detected and protected, and the NSBT is used, the proposed algorithm reaches the state-of-the-art effect which realizes both despeckling and preserving edges and details simultaneously. Experimental results show that both the subjective visual effect and the mainly objective performance indexes of the proposed algorithm outperform that of both Bayesian wavelet shrinkage with edge detection and Bayesian least square-Gaussian scale mixture （BLS-GSM）.

关键词： computer image processing synthetic aperture radar speckle edge detection nonsubsampled second generation bandelet transform Canny operator threshold shrinkage.

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Difference of inflow and outflow based 3D streamline placement 10

Difference of inflow and outflow based 3D streamline placeme...

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Proceedings of the 3rd International Symposium on Visual Information Communication

作者： Wang, Shaorong Chen, Yisong Li, Sheng Wang, Guoping Key Lab. of Machine Perception and Intelligent MOE Beijing 100871 China School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

ISBN: (纸本)9781450304368

Streamline based method is one of the most important vector field visualization methods. In the past streamline placements algorithms, little physical related feature was considered, which is very important in our opinion. A novel streamline placement algorithm for 3D vector field is introduced in this paper. We measure the difference between the inflow and the outflow to evaluate the local spatial-varying feature at a specified field point. A Difference of Inflow and Outflow Matrix (DIOM) is then calculated to describe the global appearance of the field. We draw streamlines by choosing the local extreme points in DIOM as seeds. DIOM is somewhat like flow divergence and is physics-related thus re-flects intrinsic characteristics of the vector field. The strategy performs well in revealing features of the vector field even with relatively few streamlines both in 3D vector field. Copyright © 2010 ACM.

关键词： Vectors

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Constrained layout optimization in satellite cabin using a multiagent genetic algorithm

Constrained layout optimization in satellite cabin using a m...

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9th International Conference on Simulated Evolution and Learning, SEAL 2012

作者： Liu, Jing Key Lab. of Intelligent Perception and Image Understanding Ministry of Education of China Xidian University 710071 China

ISBN: (纸本)9783642348587

One application of constrained layout optimization problems (CLOPs) is to lay out the instruments in satellite cabin (CLOPssc), which concerns the two dimensional physical placement of a collection of objects within a satellite cabin. CLOPssc are not only of significant theoretical interest, but also of real practical significance in industrial applications. In this paper, we use a multiagent genetic algorithm with a simple technique of handling constraints to solve CLOPssc. In experiments, the performance of the new algorithm is compared with existing algorithms on three benchmark problems with different complexities. Experimental results show that the new algorithm has a better global searching ability. Especially, it found a currently best solution for the constrained layout problem with 40 objects. © 2012 Springer-Verlag.

关键词： Genetic algorithms

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Compressive sensing image reconstruction based on stage-wise directional pursuit searching in the WBCT domain

Compressive sensing image reconstruction based on stage-wise...

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MIPPR 2009 - Automatic Target Recognition and Image Analysis: 6th International Symposium on Multispectral Image Processing and Pattern Recognition

作者： Si, Xiaoyun Jiao, Licheng Feng, Hongxiao Yang, Dongdong Yu, Hang Key Lab. of Intelligent Perception and Image Understanding of Ministry of Education of China Xidian University Xi'an 710071 China

ISBN: (纸本)9780819478061

In the past, it is the Nyquist sampling theory the central principal of signal processing, and most of the data we acquire can be dropped off with nearly no perceptual loss. However, an emerging theory named "compressive sensing" has been taking the place, which shows that super-resolved images can be reconstructed from extremely fewer measurements than what is generally considered necessary. In this paper, under the theoretical compressive sensing framework, we recommend the optimally- jittered undersampling, the wavelet-based contourlet transform and the stage-wise directional pursuit as the three main ingredients -a sampling strategy, a sparse transform and a recovery algorithm to recover images with and without noises. Some standard gray and color images are tested in the experiments, turning out that we only use measurements that around 40 percent of the original size to reconstruct images within high PSNR value and favorable vision impression, which means that we will dramatically reduce measurement time, sampling rates, and the use of analog-to-digital converter resources in certain corresponding practice domain. © 2009 Copyright SPIE - The International Society for Optical Engineering.

关键词： Image reconstruction

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A contourlet-based interpolation restoration method for super-resolution of SAR image

A contourlet-based interpolation restoration method for supe...

引用

2009 Asia-Pacific Conference on Synthetic Aperture Radar, APSAR 2009

作者： Zhang, Xiaohua Cao, Kun Jiao, Licheng Key Lab. of Intelligent Perception and Image Understanding of the Ministry of Education of China Institute of Intelligent Information Processing Xidian University Xi'an 710071 China

ISBN: (纸本)9781424427314

As is well known that the quality of a digital image is affected by many factors, such as the distance between the acquisition system and the object, the acquisition environment conditions, and the resolution of the image sensors employed, and so on. So how to obtain high quality images has become a difficult task in practical applications. Image super-resolution reconstruction (SRR) is a signal processing approach which can produces a high-resolution (HR) image from observed multiple low-resolution (LR) images. The purpose of this study is to evaluate the potential application of SR techniques to synthetic aperture radar (SAR). In this paper, a LR image is used to extract high frequency information and reconstruct a high resolution image by an interpolation- restoration method based on contourlet transform to solve the problem of SRR. Experimental results show that the method has the superior performance in subjective visual quality. ©2009 IEEE.

关键词： Image reconstruction

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