ASKME: adaptive sampling with knowledge-driven vectorization of mechanical engineering drawings

We propose here an efficient algorithm for high-level vectorization of scanned images of mechanical engineering drawings. The algorithm is marked by several novel features, which merit its superiority over the existing techniques. After preprocessing and necessary refinement of junction points in the image skeleton, it first extracts the graphic primitives, such as lines, circles, and arcs, based on certain digital geometric properties of straightness and circularity in the discrete domain. The primitives are classified into different types with all associated details based on fast and efficient geometric analysis. The vector set is succinctly reduced by such classification in tandem with further consolidation to make out meaningful objects like rectangles and annuli, together with hatching information. Exhaustive testing shows the efficiency of the algorithm and also its robustness and stability toward any affine transformation and injected noise. Easy reconstruction to scalable vector graphics demonstrates its readiness and usability as a state-of-the-art solution.     

An Efficient 2½ D rendering and Compositing System

We describe a method for doing image compositing using either 2D geometric shapes or raster images as input primitives. The resolution of the final image is virtually unlimited but, as no frame buffer is used, performance is much less dependant on resolution than with standard painting programs, allowing rendering very large images in reasonable time. Many standard features found in compositing programs have been implemented, like hierarchical data structures for input primitives, lighting control for each layer and filter operations (for antialiasing or defocus).     

VISTO: A new CBIR system for vector images

In this paper, we present the main features of VISTO (Vector Image Search TOol), a new content-based image retrieval (CBIR) system for vector images. Though unsuitable for photo-realistic imagery, vector graphics are continually becoming more advanced and diffused. Vector images are fully scalable, resolution independent, not restricted to rectangular shape, allowing layering and editable/searchable text. Notwithstanding this increasing interest, the research area concerning CBIR systems for vectorial images is quite new, and our research on a vector based CBIR system actually derives from a precise request of vector based application experts that did not find appropriate solutions to their retrieval problems in customary shape-based CBIR system. To the best of our knowledge, VISTO is the first CBIR system for vector images proposed in the literature, and it supports the retrieval of images in SVG (scalable vector graphics) format.     

Super TEX-SIM: Interactive textile design and simulation

This paper presents an interactive tool for designing and simulating textile images. It comprises a yarn editor, a textile editor and a texture mapper. These subsystems share a colour editor that can modify the colours of yarn and textile images interactively. We describe how yarn and textile images are generated, and how they are mapped to a target picture read from an image scanner. The user interface in the tool has many useful functions so that users can design textile images without knowledge of computer graphics and programming languages. Several examples of texture mapping are included.     

Multi-circle detection on images inspired by collective animal behavior

Hough transform (HT) has been the most common method for circle detection that delivers robustness but adversely demands considerable computational efforts and large memory requirements. As an alternative to HT-based techniques, the problem of shape recognition has also been handled through optimization methods. In particular, extracting multiple circle primitives falls into the category of multi-modal optimization as each circle represents an optimum which must be detected within the feasible solution space. However, since all optimization-based circle detectors focus on finding only a single optimal solution, they need to be applied several times in order to extract all the primitives which results on time-consuming algorithms. This paper presents an algorithm for automatic detection of multiple circular shapes that considers the overall process as a multi-modal optimization problem. In the detection, the approach employs an evolutionary algorithm based on the way in which the animals behave collectively. In such an algorithm, searcher agents emulate a group of animals which interact to each other using simple biological rules. These rules are modeled as evolutionary operators. Such operators are applied to each agent considering that the complete group maintains a memory which stores the optimal solutions seen so-far by applying a competition principle. The detector uses a combination of three non-collinear edge points as parameters to determine circle candidates (possible solutions). A matching function determines if such circle candidates are actually present in the image. Guided by the values of such matching functions, the set of encoded candidate circles are evolved through the evolutionary algorithm so that the best candidate (global optimum) can be fitted into an actual circle within the edge-only image. Subsequently, an analysis of the incorporated memory is executed in order to identify potential local optima which represent other circles. Experimental results over several complex synthetic and natural images have validated the efficiency of the proposed technique regarding accuracy, speed and robustness.     

基于可伸缩矢量图形的手绘几何图形结构分析方法

复杂图形通常是由多个图元按一定几何关系构成,以基本图形的识别为基础,复杂图形识别重点在于图形元素之间的空间关系模式的判定。几何图形的图元构成复杂,难以直接利用启发式规则进行识别;而现有的结构分析方法太复杂,采用传统方法难以进行有效识别。针对手绘几何图形识别中结构分析这一核心技术问题,设计了一种几何图形结构描述模型,该模型通过对图元及其约束关系的形式化描述来表示图形,使用可伸缩矢量图形(SVG)标签存储图元及其约束,通过解析SVG标签来识别几何图形的形状及其内部关系,为图形结构分析提供了统一格式的表示方法。所提方法已经过自主开发的GeoSketch系统的验证,并取得良好效果。实验结果表明:该方法简洁、低维,方便进行图形形状及内部关系的判定。     

基于直线段跟踪的手绘图元离线识别方法*

手绘图形是人类思维外化和表达意图的一种有效方式,如何有效地提取手绘在图纸上的图形元素是理解绘图者意图的关键问题。鉴于手绘图形是由基本图元组合构成,采用层次结构逐步实现图元提取的思想,提出了一种手绘基本图元（线段、弧、圆和椭圆）的离线识别方法。在提取图形笔画骨架像素的基础上,跟踪骨架像素得到图形的直线段描述;通过对直线段序列的分析,进行直线段序列的断开和连接处理,形成图元的曲线段描述,通过对图元曲线段描述的分析得出图元的几何参数。实验表明,该方法能够以高精确度快速识别出图像中包含的手绘图元,具有良好的稳定性     

Interlocking shapes in art and engineering

This paper reviews the art and science of interlocking shapes. With the help of computer graphics, such a design technique is now available to many people and original drawings composed by engineering students are included here. The computer has served as a creative tool and a teaching tool. New engineering applications of interlocking shapes are now within reach.     

数字近景工业摄影测量中基于方位圆的相机标定方法研究

针对目前数字近景工业摄影测量中常用标定方法使用上的局限性,提出了一种基于方位圆的相机标定新方法.首先,使用带有5个方位圆的圆形标定板获取图像序列并进行预处理,利用椭圆检测准则剔除冗余信息,确定出所有标志点;然后,根据方位圆之间特殊的几何关系,从识别方位圆出发,完成标定板上所有标志点从物空间到像空间的自动匹配;最后,求解出相机内参数并结合高斯-牛顿法对内参数进行优化,从而进一步提高测量精度.提出的方法和理论通过在Matlab 2010中对所拍摄的一组图片进行实验验证,结果表明具有较好的鲁棒性,可以满足工业摄影测量的精度要求.     

The convergence of graphics and vision

Computer graphics and computer vision are inverse problems. Traditional computer graphics starts with input geometric models and produces image sequences. Traditional computer vision starts with input image sequences and produces geometric models. Lately, there has been a meeting in the middle, and the center, the prize, is to create stunning images in real time. Vision researchers now work from images backward, just as far backward as necessary to create models that capture a scene without going to full geometric models. Graphics researchers now work with hybrid geometry and image models. Approaching similar problems from opposite directions, graphics and vision researchers are reaching a fertile middle ground. The goal is to find the best possible tools for the imagination. This overview describes cutting edge work, some of which will debut at Siggraph 98     

Telidon graphics and applications

Telidon is essentially a computer graphics code which is very effective as the presentation level protocol for videotex, for which it was originally developed, teletext and other consumer- and business-oriented information systems. Its use of geometric primitives rather than the mosaic characters of its predecessors permits efficient digital storage and rapid transmission of detailed graphics. Display terminals can be built to display the images with different degrees of detail to suit the application.     

Fast display of illuminated field lines

A new technique for interactive vector field visualization using large numbers of properly illuminated field lines is presented. Taking into account ambient, diffuse and specular reflection terms, as well as transparency and depth cueing, we employ a realistic shading model which significantly increases the quality and realism of the resulting images. While many graphics workstations offer hardware support for illuminating surface primitives, usually no means for an accurate shading of line primitives are provided. However, we show that proper illumination of lines can be implemented by exploiting the texture mapping capabilities of modern graphics hardware. In this way, high rendering performance with interactive frame rates can be achieved. We apply the technique to render large numbers of integral curves of a vector field. The impression of the resulting images can be further improved by a number of visual enhancements, like color coding or particle animation. We also describe methods for controlling the distribution of field lines in space. These methods enable us to use illuminated field lines for interactive exploration of vector fields     

Shading Curves: Vector‐Based Drawing With Explicit Gradient Control

A challenge in vector graphics is to define primitives that offer flexible manipulation of colour gradients. We propose a new primitive, called a shading curve, that supports explicit and local gradient control. This is achieved by associating shading profiles to each side of the curve. These shading profiles, which can be manually manipulated, represent the colour gradient out from their associated curves. Such explicit and local gradient control is challenging to achieve via the diffusion curve process, introduced in 2008, because it offers only implicit control of the colour gradient. We resolve this problem by using subdivision surfaces that are constructed from shading curves and their shading profiles.     

Display of surfaces from volume data

The application of volume-rendering techniques to the display of surfaces from sampled scalar functions of three spatial dimensions is discussed. It is not necessary to fit geometric primitives to the sampled data; images are formed by directly shading each sample and projecting it onto the picture plane. Surface-shading calculations are performed at every voxel with local gradient vectors serving as surface normals. In a separate step, surface classification operators are applied to compute a partial opacity of every voxel. Operators that detect isovalue contour surfaces and region boundary surfaces are examined. The technique is simple and fast, yet displays surfaces exhibiting smooth silhouettes and few other aliasing artifacts. The use of selective blurring and supersampling to further improve image quality is described. Examples from molecular graphics and medical imaging are given     

From on-line sketching to 2D and 3D geometry: a system based on fuzzy knowledge

The paper describes the development of a fuzzy knowledge-based prototype system for conceptual design. This real time system is designed to infer user's sketching intentions, to segment sketched input and generate corresponding geometric primitives: straight lines, circles; arcs, ellipses, elliptical arcs, and B-spline curves. Topology information (connectivity, unitary constraints and pairwise constraints) is received dynamically from 2D sketched input and primitives. From the 2D topology information, a more accurate 2D geometry can be built up by applying a 2D geometric constraint solver. Subsequently, 3D geometry can be received feature by feature incrementally. Each feature can be recognised by inference knowledge in terms of matching its 2D primitive configurations and connection relationships. The system accepts not only sketched input, working as an automatic design tool, but also accepts user interactive input of both 2D primitives and special positional 3D primitives. This makes it easy and friendly to use. The system has been tested with a number of sketched inputs of 2D and 3D geometry.