Efficient extraction of primitives from line drawings composed of horizontal and vertical lines

The performance of the algorithms for the extraction of primitives for the interpretation of line drawings is usually affected by the degradation of the information contained in the document due to factors such as low print contrast, defocusing, skew, etc. In this paper, we are proposing two algorithms for the extraction of primitives with good performance under degradation. The application of the algorithms is restricted to line drawings composed of horizontal and vertical lines. The performance of the algorithms has been evaluated by using a protocol described in the literature. Received: 6 August 1996 / Accepted: 16 July 1997     

A system to understand hand-drawn floor plans using subgraph isomorphism and Hough transform

Presently, man-machine interface development is a widespread research activity. A system to understand hand drawn architectural drawings in a CAD environment is presented in this paper. To understand a document, we have to identify its building elements and their structural properties. An attributed graph structure is chosen as a symbolic representation of the input document and the patterns to recognize in it. An inexact subgraph isomorphism procedure using relaxation labeling techniques is performed. In this paper we focus on how to speed up the matching. There is a building element, the walls, characterized by a hatching pattern. Using a straight line Hough transform (SLHT)-based method, we recognize this pattern, characterized by parallel straight lines, and remove from the input graph the edges belonging to this pattern. The isomorphism is then applied to the remainder of the input graph. When all the building elements have been recognized, the document is redrawn, correcting the inaccurate strokes obtained from a hand-drawn input. Received 6 June 1996 / Accepted 4 February 1997     

Registration of technical drawings and calibrated images for industrial augmented reality

Despite tremendous progress in 3D modelling technology, most sites in traditional industries do not have a computer model of their facilities at their disposal. In these industries, 2D technical drawings are typically the most commonly used documents. In many cases, a database of fully calibrated and oriented photogrammetric images of parts of the plant is also available. These images are often used for metric measurement and 3D as-built modelling. For planning revamps and maintenance, it is necessary to use industrial drawings as well as images and 3D models represented in a common “world” coordinate system. This paper proposes a method for full integration of technical drawings, calibrated images and as-built 3D models. A new algorithm is developed in order to use only a few correspondences between points on a technical drawing and multiple images to estimate a metric planar transformation between the drawing and the world coordinate system. The paper describes the mathematical relationship between this transformation and the set of homographies needed for merging the technical drawing with all the calibrated images. The method is implemented and fully integrated into an industrial software we developed for 3D as-built reconstruction. We present examples of a real application, in which the method is successfully applied to create an augmented reality representation of a waste water plant. Accepted: 13 August 2001     

An architecture for handwritten text recognition systems

This paper presents an end-to-end system for reading handwritten page images. Five functional modules included in the system are introduced in this paper: (i) pre-processing, which concerns introducing an image representation for easy manipulation of large page images and image handling procedures using the image representation; (ii) line separation, concerning text line detection and extracting images of lines of text from a page image; (iii) word segmentation, which concerns locating word gaps and isolating words from a line of text image obtained efficiently and in an intelligent manner; (iv) word recognition, concerning handwritten word recognition algorithms; and (v) linguistic post-pro- cessing, which concerns the use of linguistic constraints to intelligently parse and recognize text. Key ideas employed in each functional module, which have been developed for dealing with the diversity of handwriting in its various aspects with a goal of system reliability and robustness, are described in this paper. Preliminary experiments show promising results in terms of speed and accuracy. Received October 30, 1998 / Revised January 15, 1999     

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.     

Robust classification of arbitrary object classes based on hierarchical spatial feature-matching

We present a novel approach to the robust classification of arbitrary object classes in complex, natural scenes. Starting from a re-appraisal of Marr's ‘primal sketch’, we develop an algorithm that (1) employs local orientations as the fundamental picture primitives, rather than the more usual edge locations, (2) retains and exploits the local spatial arrangement of features of different complexity in an image and (3) is hierarchically arranged so that the level of feature abstraction increases at each processing stage. The resulting, simple technique is based on the accumulation of evidence in binary channels, followed by a weighted, non-linear sum of the evidence accumulators. The steps involved in designing a template for recognizing a simple object are explained. The practical application of the algorithm is illustrated, with examples taken from a broad range of object classification problems. We discuss the performance of the algorithm and describe a hardware implementation. First successful attempts to train the algorithm, automatically, are presented. Finally, we compare our algorithm with other object classification algorithms described in the literature.     

Display Design of Process Systems Based on Functional Modelling

The prevalent way to present information in industrial computer displays is by using piping and instrumentation diagrams. Such interfaces have sometimes resulted in difficulties for operators because they are not sufficient to fulfil their needs. A systematic way that supports interface design therefore has to be considered. In the new design framework, two questions must be answered. Firstly, a modelling method is required to describe a process system. Such a modelling method can define the information content that must be displayed in interfaces. Secondly, how to communicate this information to operators efficiently must be considered. This will provide a basis for determining the visual forms that the information should take. This study discusses interface design of human–machine systems from these two points of view. Based on other scholars’ work, a comprehensive set of functional primitives is summarised as a basis to build a functional model of process systems. A library of geometrical presentations for these primitives is then developed. To support effective interface design, the concept of ‘functional macro’ is introduced and a way to map functional model to interface display is illustrated by applying several principles. To make our ideas clear, a central heating system is taken as an example and its functional model is constructed. Based on the functional model, the information to be displayed is determined. Several functional macros are then found in the model and their corresponding displays are constructed. Finally, by using the library of geometrical presentations for functional primitives and functional macros, the display hierarchy of the central heating system is developed. Reusability of functional primitives makes it possible to use the methodology to support interface design of different process systems.     

Integrating symbolic images into a multimedia database system using classification and abstraction approaches

Symbolic images are composed of a finite set of symbols that have a semantic meaning. Examples of symbolic images include maps (where the semantic meaning of the symbols is given in the legend), engineering drawings, and floor plans. Two approaches for supporting queries on symbolic-image databases that are based on image content are studied. The classification approach preprocesses all symbolic images and attaches a semantic classification and an associated certainty factor to each object that it finds in the image. The abstraction approach describes each object in the symbolic image by using a vector consisting of the values of some of its features (e.g., shape, genus, etc.). The approaches differ in the way in which responses to queries are computed. In the classification approach, images are retrieved on the basis of whether or not they contain objects that have the same classification as the objects in the query. On the other hand, in the abstraction approach, retrieval is on the basis of similarity of feature vector values of these objects. Methods of integrating these two approaches into a relational multimedia database management system so that symbolic images can be stored and retrieved based on their content are described. Schema definitions and indices that support query specifications involving spatial as well as contextual constraints are presented. Spatial constraints may be based on both locational information (e.g., distance) and relational information (e.g., north of). Different strategies for image retrieval for a number of typical queries using these approaches are described. Estimated costs are derived for these strategies. Results are reported of a comparative study of the two approaches in terms of image insertion time, storage space, retrieval accuracy, and retrieval time. Received June 12, 1998 / Accepted October 13, 1998     

Analyzing scenery images by monotonic tree

Content-based image retrieval (CBIR) has been an active research area in the last ten years, and a variety of techniques have been developed. However, retrieving images on the basis of low-level features has proven unsatisfactory, and new techniques are needed to support high-level queries. Research efforts are needed to bridge the gap between high-level semantics and low-level features. In this paper, we present a novel approach to support semantics-based image retrieval. Our approach is based on the monotonic tree, a derivation of the contour tree for use with discrete data. The structural elements of an image are modeled as branches (or subtrees) of the monotonic tree. These structural elements are classified and clustered on the basis of such properties as color, spatial location, harshness and shape. Each cluster corresponds to some semantic feature. This scheme is applied to the analysis and retrieval of scenery images. Comparisons of experimental results of this approach with conventional techniques using low-level features demonstrate the effectiveness of our approach.     

Query by video clip

Typical digital video search is based on queries involving a single shot. We generalize this problem by allowing queries that involve a video clip (say, a 10-s video segment). We propose two schemes: (i) retrieval based on key frames follows the traditional approach of identifying shots, computing key frames from a video, and then extracting image features around the key frames. For each key frame in the query, a similarity value (using color, texture, and motion) is obtained with respect to the key frames in the database video. Consecutive key frames in the database video that are highly similar to the query key frames are then used to generate the set of retrieved video clips. (ii) In retrieval using sub-sampled frames, we uniformly sub-sample the query clip as well as the database video. Retrieval is based on matching color and texture features of the sub-sampled frames. Initial experiments on two video databases (basketball video with approximately 16,000 frames and a CNN news video with approximately 20,000 frames) show promising results. Additional experiments using segments from one basketball video as query and a different basketball video as the database show the effectiveness of feature representation and matching schemes.     

Some unusual primitives in the mira graphical extension of PASCAL

The MIRA system is a very general graphics system which may be useful for almost anyone interested in the production of drawings. The system allows the user to create, save, retrieve, modify and delete any kind of drawing: e.g. free-hand drawings, drawings based on geometrical primitives, algorithmic drawings, data plots, texts. Two-dimensional and three-dimensional drawings can be manipulated. The MIRA system is based on two graphical PASCAL extensions MIRA-2D and MIRA-3D. Two interactive graphical editors GRAFEDIT (two dimensions) and HORIZON (three dimensions) allow the non-specialist user to build complex drawings easily.After an overview of the MIRA system, we present the most unusual primitives, which have been developed for use with this system. These primitives can be divided into different classes: graphical types, figure algebra primitives, figure measure functions, figure recognition predicates, image transformations and animation primitives.     

Defect detection in textured surfaces using color ring-projection correlation

In this paper, we present a correlation scheme that incorporates a color ring-projection representation for the automatic inspection of defects in textured surfaces. The proposed color ring projection transforms a 2-D color image into a 1-D color pattern as a function of radius. For a search window of width W, data dimensionality is reduced from in the 2-D image to O(W) in the 1-D ring-projection space. The complexity of computing a correlation function is significantly reduced accordingly. Since the color ring-projection representation is invariant to rotation, the proposed method can be applied for both isotropic and oriented textures at arbitrary orientations. Experiments on regular textured surfaces have shown the efficacy of the proposed method. Received: 30 March 2000 / Accepted: 24 July 2001 Correspondence to: D.-M. Tsai (e-mail: iedmtsai@saturn.yzu.edu.tw)     

Multiresolution volume visualization with a texture-based octree

Although 3D texture-based volume rendering guarantees image quality almost interactively, it is difficult to maintain an interactive rate when the technique has to be exploited on large datasets. In this paper, we propose a new texture memory representation and a management policy that substitute the classical one-texel per voxel approach for a hierarchical approach. The hierarchical approach benefits nearly homogeneous regions and regions of lower interest. The proposed algorithm is based on a simple traversal of the octree representation of the volume data. Driven by a user-defined image quality, defined as a combination of data homogeneity and importance, a set of octree nodes (the cut) is selected to be rendered. The degree of accuracy applied for the representation of each one of the nodes of the cut in the texture memory is set independently according to the user-defined parameters. The variable resolution texture model obtained reduces the texture memory size and thus texture swapping, improving rendering speed.     

Adaptive image-smoothing using a coplanar matrix and its application to document image binarization

Abstract. For document images corrupted by various kinds of noise, direct binarization images may be severely blurred and degraded. A common treatment for this problem is to pre-smooth input images using noise-suppressing filters. This article proposes an image-smoothing method used for prefiltering the document image binarization. Conceptually, we propose that the influence range of each pixel affecting its neighbors should depend on local image statistics. Technically, we suggest using coplanar matrices to capture the structural and textural distribution of similar pixels at each site. This property adapts the smoothing process to the contrast, orientation, and spatial size of local image structures. Experimental results demonstrate the effectiveness of the proposed method, which compares favorably with existing methods in reducing noise and preserving image features. In addition, due to the adaptive nature of the similar pixel definition, the proposed filter output is more robust regarding different noise levels than existing methods. Received: October 31, 2001 / October 09, 2002 Correspondence to:L. Fan (e-mail: fanlixin@ieee.org)