工程图纸矢量化软件的设计与实现

工程图纸矢量化是把扫描所得到的光栅图像加以处理、分析、识别，并最终转换成矢量图形格式的过程。矢量化研究是图纸复用、自动理解等应用的基础，是目前CAD领域的一个研究热点。文中介绍了所开发的工程图纸矢量化软件的设计思想和实现技术，包括图像处理和图形自动识别算法,以及为了进一步提高矢量化的准确率而采用的光栅图像编辑和矢量图形编辑等人机交互方法。实验结果证明了以上诸多方法的有效性，软件基本上达到了实用水平。     

工程图纸矢量化软件的设计与实现

工程图纸矢量化是把扫描所得到的光栅图像加以处理、分析、识别,并最终转换成矢量图形格式的过程.矢量化研究是图纸复用、自动理解等应用的基础,是目前CAD领域的一个研究热点.文中介绍了所开发的工程图纸矢量化软件的设计思想和实现技术,包括图像处理和图形自动识别算法,以及为了进一步提高矢量化的准确率而采用的光栅图像编辑和矢量图形编辑等人机交互方法.实验结果证明了以上诸多方法的有效性,软件基本上达到了实用水平.     

拓扑关系在图形对象表示与识别中的应用

工程图纸识别中,图形对象的表示方法是研究的重点和难点。在矢量化的基础上提出了一种基于拓扑结构的图形对象表示与识别方法,该方法通过矢量化获得各个图形对象的矢量基元,通过建立矢量基元的影响区域确定各矢量基元的拓扑邻接关系图,进而确定图形对象之间的位置关系,为进一步理解识别工程图纸提供了基本的信息。然后介绍了一个应用实例：圆弧角的识别。在实验中,分别用标准数据和真实图纸进行了测试,实验结果显示该算法具有较高的识别精度和识别效率。     

工程图矢量化中图文分离的一种快速算法

工程图纸通常是由图形和文字符合两部分组成，由于在矢量化中对图形和文字进一步处理的要求不同，故在矢量化之前把工程图中的图形和文字符号区分开来是十分重要的。本文提出了一种工程图矢量化图文分离算法，它能有效地将图形和文字分开，这种算法不仅可以减少多余的数据量，加快后期的线条提取速度，而且可使数据的关系更为清晰明了，分离出来的符号文件保留了其原来在图纸中的位置，为文字符号的识别或重新写入提供了方便。     

基于节点区域分离的工程图纸整体识别方法

在工程图纸矢量化处理中着眼于图形的宏观特征,提出了一种整体识别方法,该方法中,引入节点区域的概念,通过节点区域与图段的连接关系确定图形的拓扑结构,并由节点区域分离分割图段,图段的跟踪识别以图段轮廓的方向码序列为引导实现。整体识别算法矢量化速度快,有较强的抗噪声能力。     

工程图纸的矢量化方法

矢量化是工程图纸自动输入和识别不可缺少的重要环节。而线段提取则是矢量化处理的关键。本文拟对工程图纸矢量化过程中图象预处理和常用的几种线段提取方法作一简要介绍和比较,同时对所用的处理给出算法描述。     

矢量字库的设计与实现

矢量字库是使用矢量文字的主要方式。本文以一种轮廓文字位图矢量化的方法为基础，详细介绍了从文字住图数据抓取、位图轮廓提取、矢量化数据生成、到矢量化字库生成、读取及显示的设计与实现方法。     

工程图纸向CAD系统自动输入处理

初步实现了一个工程图纸的自动输入与识别系统。该系统把工程图纸的扫描数字化图象进行矢量化,转换成CAD系统可以接受的文件格式。研究了扫描图象的预处理和矢量化方法:预处理包括图纸扫描输入、图象二值化、图象平滑与去噪、线条细化和曲线跟踪;矢量化采用直线拟合方法。提出了一种改进Hilditch细化算法并给出了程序实现方法,有效地减小了图像骨架偏移和毛刺对细化结果的影响。该文开发的系统可以识别含有直线、圆和圆弧等简单图形的工程图纸。     

光栅矢量混合编辑技术的研究与实现

本文介绍一个实用化的工程图纸处理系统－ＥＤＤ／ＡｕｔｏＣＡＤ，该系统可以将扫描后的光栅图纸装入到ＡｕｔｏＣＡＤ编辑环境中，直接对光栅图进行编辑修改，或利用矢量化工具技术转成矢量图形，本文就系统涉及到光栅矢量混合编辑技术，矢量化技术等关键技术提出了新的解决办法，并进行了讨论。     

彩色光栅图像的矢量化

彩色图像的矢量化在很多领域都有着重要的应用,例如制作在网上非常流行的精美的生动形象的矢量动画,实现彩色地图的GIS系统等。文中提出了一种对彩色图像进行矢量化的方法．并给出了相应处理过程和算法流程。该矢量化方法根据彩色图像的特点,在处理过程中引入HSI彩色空间,利用轮廓提取和跟踪技术,完成了对彩色图像的矢量化。经试验表明,该算法有一定的实用性。     

曲面体线图的标记与匹配

三维曲面体的标记与匹配,是计算机视觉研究领域中一项相当有用但又是非常困难的技术。本文讨论了一种曲面体标记的新方法。通过引入线段的一些新的标记类型,圆满地解决了利用 Huffman 标记技术描述曲面体时,可能出现的不一致性。根据以上的标记结果,本文还给出了一匹配曲面体线图的新方法。在匹配过程中,我们注重的不是图象的二维特征,而是其对应的物体的三维特征,因而对物体的旋转、遮挡、尺度变化及远视失真等极不敏感。实验结果表明本算法是相当令人满意的。     

基于面域理解的多面体三维重建

已有的三维重建算法一般是从点线或体的角度来理解视图,实际上,视图中的环包含了 大量的形体面信息,可以直接从中间层次的面理解形体的投影。文中根据实体构成和平面投影的约束和规则重建显式表达的面,并进一步推导出隐式表达的面,从而得到完整的形体边界模型,本算法适用于平面多面体,通过面域作为中介,容易实现与模型引导方法的融合,从而拓展到二次曲面体的重建。     

Matching perspective views of a polyhedron using circuits

We present a novel approach for finding corresponding points between two line drawings extracted from perspective views of a moving object whose surface is composed of planar polygons. In our approach, each circuit of the drawings is encoded with a boundary shape code which we call the RLCC code (run length code of convex and concave strings), then a clustering technique is used to obtain the matching result recursively. A series of measures are taken to make the algorithm tolerate considerable dissimilarities which may exist between the two drawings, such as missing lines, scale differences, rotation, perspective shape distortions, etc. Experimental results are presented.     

Animated 3D Line Drawings with Temporal Coherence

Producing traditional animation is a laborious task where the key drawings are first drawn by artists and thereafter inbetween drawings are created, whether it is by hand or computer‐assisted. Auto‐inbetweening of these 2D key drawings by computer is a non‐trivial task as 3D depths are missing. An alternate approach is to generate all the drawings by extracting lines directly from animated 3D models frame by frame, concatenating and rendering them together into an animation. However, animation quality generated using this straightforward method bears two problems. Firstly, the animation contains unsatisfactory visual artifacts such as line flickering and popping. This is especially pronounced when the lines are extracted using high‐order derivatives, such as ridges and valleys, from 3D models represented in triangle meshes. Secondly, there is a lack of temporal continuity as each drawing is generated without taking its neighboring drawings into consideration. In this paper, we propose an improved approach over the straightforward method by transferring extracted 3D line drawings of each frame into individual 3D lines and processing them along the time domain. Our objective is to minimize the visual artifacts and incorporate temporal relationship of individual lines throughout the entire animation sequence. This is achieved by creating correspondent trajectory of each line from each frame and applying global optimization on each trajectory. To realize this target, we present a fully automatic novel approach, which consists of (1) a line matching algorithm, (2) an optimizing algorithm, taking into account both the variations of numbers and lengths of 3D lines in each frame, and (3) a robust tracing method for transferring collections of line segments extracted from the 3D models into individual lines. We evaluate our approach on several animated model sequences to demonstrate its effectiveness in producing line drawing animations with temporal coherence.     

Real time egomotion of a nonholonomic vehicle using LIDAR measurements

This paper presents a technique to estimate in real time the egomotion of a vehicle based solely on laser range data. This technique calculates the discrepancy between closely spaced two‐dimensional laser scans due to the vehicle motion using scan matching techniques. The result of the scan alignment is converted into a nonlinear motion measurement and fed into a nonholonomic extended Kalman filter model. This model better approximates the real motion of the vehicle when compared to more simplistic models, thus improving performance and immunity to outliers. The motion estimate is intended to be used for egomotion compensation in a target‐tracking algorithm for situation awareness applications. In this paper, several recent scan matching algorithms were evaluated for their accuracy and computational speed: metric‐based iterative closest point (MbICP), point‐to‐line ICP (PIICP), and polar scan matching. The proposed approach is performed in real time and provides an accurate estimate of the current robot motion. The MbICP algorithm proved to be the most advantageous scan matching algorithm, but it is still comparable to PlICP. The motion estimation algorithm is validated through experimental testing in real world conditions.     

基于改进的NRLCC编码的立体线图匹配算法

线图匹配在计算机视觉领域有着广泛的应用。该文研究基于改进的NRLCC编码以及面之间的关系进行立体线图的匹配。首先利用图同构检测目标线图与模型线图的面的排列关系是否一致;然后获取面的NRLCC编码和ENRLCC编码,分别得到面的顶点的凹凸性信息和组成面的曲线段的凹凸性信息。最后,利用以上几组信息,进行线图的匹配。试验结果表明,该方法可以对具有曲线边缘的工业物体进行准确的识别。     

一种新的基于特征点的立体匹配算法

目前,立体匹配是计算机视觉领域中最活跃的研究主题之一。为了快速并更精确的对特征点进行立体匹配,本文提出了一种新的基于特征点的立体匹配算法。该方法独立于特征点的检测算法,先以扫描线作为匹配单元,然后以鲁棒函数为匹配代价函数,最后用顺序约束对每一匹配单元的视差图进行检测与校正。实验证明,该方法的匹配精度高于传统的基于NCC(norm alized cross-correlation)的立体匹配算法,并且运行时间快,可以应用于纯软件的基于特征点的立体视觉系统中。     

A Line Extraction Algorithm for Hand Drawings

This paper presents an algorithm for extracting lines from hand drawings.It starts from contour pixel tracing,fits them into contour segments,and then extracts skeleton lines from the contour segments.The algorithm finds all contours in one scan of the input matrix without detecting and marking multiple pixels.In line extraction,the method Elastic Contour Segment Tracing is proposed which extracts lines by referring to the contour segments at both sides,overcoming noise and passing through blotted areas by fitting and extrapolation. Experiments on free hand mechanical drawings,sketches,letter/numerals,as well as Chinese characters are carried out and satisfactory results are achieved.     

Computer-assisted coloring by matching line drawings

An approach to automatically color line drawings based on feature matching is proposed. The motivation is that coloring 2D animation is still a labor-intensive process in current cartoon film production. The objective of our work is to investigate how to automatically color an image in a cartoon sequence on the basis of the previous frame. Our method first establishes the matching relationship of two images, after which it automatically paints one of them with the color information of the other using a region-matching algorithm. The region-matching algorithm is based on feature correspondences. The results show that the proposed algorithm can straightforwardly and robustly realize our objective and has a promising future for our next step to further automate conventional animation.