Takeo Yaku

Ridge Detection with the Steepest Ascent Method

We propose a new method to detect ridges from digital elevation map (DEM) data. We call it “the steepest ascent method” which is based on steepest ascent lines obtained by selecting the maximum inclined direction from eight neighbors. Then ridge lines are extracted by their steepest ascent lines on a surface. In this paper it is shown that our method is able to detect ridge lines sharply. Besides we claim that our algorithm is simple and suitable for huge area such as the entire area of Japan. Finally, we give the ridge detected terrain map of the entire area of Japan and Korea by applying “the steepest ascent method”.

An NCE context-sensitive graph grammar for visual design languages

An NCE context-sensitive graph grammar, that is, a context-sensitive graph grammar with neighborhood controlled embedding has been developed. It is an expansion of the well-known NCE (context-free) graph grammar. Because it has a quite general embedding mechanism, it can be used to formalize the graph-syntax rules of visual objects with much flexibility. The composition of its production copies is discussed. It is theoretically and practically significant for defining graph-rewriting rules that can be (re)used to embed sub-graphs of particular structures, such as the feedback structure of control systems and the frequently-used sub-diagrams of program diagrams. The confluence property of NCE context-sensitive graph grammars is also studied. This property maintains that the result of a derivation does not depend on the order in which the production copies were applied. This is very important for guaranteeing the validity of the application of composite production copies and for developing efficient parsing algorithms. This formalization of subgraph reuse on, the basis of composite production copies is widely applicable to visual design languages based on graph grammars.

A resolution reduction method for multi-resolution terrain maps

Raster images such as raster terrain maps are commonly used in computer graphics. For rapid processing such as rendering and rapid feature extraction, rapid resolution reduction methods are required that keep the quality of huge images. This study deals with the resolution reduction methods.

Geographical Concept Recognition With the Octgrid Method for Learning Geography and Geology

Recognizing geographical concepts such as ridges, valleys, and contour lines is an important issue in geography learning. We provide a system for automatic recognition of such concepts based on a data structure, OCTGRIDs for landforms. Furthermore, we apply the systems to a CAI system for geology and geography.

8k-ary Grid graph models of tabular forms

Tabular forms are commonly used in software. Those tabular forms are represented as rectangular dissections. In rectangular dissections, ruled line oriented operations such as cell merge, line and column operations are often used. With respect to ruled line oriented operations, 8k-ary grid graphs have been introduced as models of rectangular dissections that provide fast algorithms. This paper surveys octal and hexa-decimal grid graph models of rectangular dissections. First, octal grids, called octgrids, for single layer rectangular dissections and related algorithms are introduced. Next, hexa-decimal grid graphs for multiple layer rectangular dissections, called hexadeci-grids, and related algorithms are introduced. Furthermore, tetraicosa-grid graphs for rectangular solid dissections for CG applications, called tetraicosa-grids and related algorithms are introduced.

The Number of Cells in Regions Shifted on 2D Images Represented by Raster Data with Heterogeneous Parts

We deal with the octgrid model which is a data structure for raster data such as 2D images, spread sheets and so forth. The octgrid model is an octal degree grid graph model and is able to handle various raster data with heterogeneous parts. In this paper, we consider change ratio of the number of cells when regions are shifted in a 2D image represented by raster data with heterogeneous parts. We propose two algorithms for translation of regions in 2D images represented by the octgrid model to compare change rates of the number of cells with ones by quad tree. And then, we describe that our algorithms by the octgrid model keep the number of cells by some examples when some regions are shifted in an image.

Tabular form editing with a hexadecimal grid graph model

We discuss tabular forms. It is known in the previous studies that the “octgrid” is a data structure for single layer tabular forms with ruled line preserving algorithms. And the “hexadeci-grid” is known as a data structure for multiply layered tabular forms which is a generalization of the “octgrid”. Our purpose of this paper is to propose a new algorithm based on the “hexadeci-grid” model for editing tabular forms.

Depth-first layout algorithm for trees

Abstract This paper deals with a layout problem of trees satisfying certain given aesthetic conditions. It is known as “tidy drawing problems of trees”. We consider a type of tree called a “tree-structured diagram” in which each node has variable size and location. In this paper, for drawing tree-type program flowcharts, we first formulate “tidy drawing problems of tree-structured diagrams” on the integral lattice. The formulation defines a tree-structured diagram and aesthetic conditions, which are modifications of the tidy drawing problem of trees. Second, we develop O(n)- and O(n2)-time algorithms to provide layouts which satisfy the conditions introduced. As a result, we obtain the relationship between the aesthetic conditions and the time complexity of algorithms.

A data structure for triangular dissection of multi-resolution images

In this work, the heterogeneous rectangular dissections that represent multi-resolution images of raster data are considered. Specifically, heterogeneous rectangular dissections are changed to triangular dissections in order to provide more effective feature extraction. We propose a method of generating triangular dissections that maintains “octgrid” properties and have developed a list structure suitable for extracting image features (ridges, valleys, etc.) from terrain maps. We propose a detailed list structure called “H12Code” and present examples of feature extraction using H12Code lists.

Generation of UML package diagrams based on an attribute graph grammar

Abstract Graphical representations are often used in software design and development because of their expressiveness. So far, various graphical program description languages have been reported. The Unified Modeling Language (UML), developed for modeling in software development was proposed recently, and in 2005 was standardized as the ISO/IEC 19501 standard. Some tools for drawing UML diagrams have been proposed in recent years. However, it is hard for developers to draw UML diagrams using the UML tool because diagram layouts generally should be manually adjusted. Of course, there are tools that can automatically provide layout diagrams, though, sometimes such functions provide unexpected layouts. In order to automate the drawing of these graphical representations aesthetically, a syntax for program diagrams must first be defined. We propose a framework for specifying these diagrams using a graph grammar, and a syntax-directed editor based on the graph grammar.