A C1 interpolation scheme for constructing surface patch on n-sided region (n5, 6) is presented. The constructed surface patch matches the given boundary curves and cross-boundary slopes on the sides of the n-sided region (n5, 6). This scheme has relatively simple construction, and offers one degree of freedom for adjusting interior shape of the constructed interpolation surface. The polynomial precision set of the scheme includes all the polynomials of degree three or less. The experiments for comparing the proposed scheme with two schemes proposed by Gregory and Varady respectively and also shown.

The information of closed curves obtained from figures is one of important features for describing them. Concerned with such kinds of studies, the feature extraction of a single closed curve has been reported in many papers. In this paper, a method of converting a collection of open-curves into that of the closed curves is proposed by supposing a smooth slope around the region including the curves with levels. As an example, contour lines of mountainous map are processed for obtaining closed contour lines.

Structure runlength coding encodes reversibly digital multi-color images. This coding processes the original images efficiently along raster scan lines. Two-dimensional structure of multi-color images is used to enhance its efficiency. The use of the structure makes the coding much more efficient than conventional runlength coding schemes. Even various gradational areas are coded effectively. This paper presents the precise coding method and compares its efficiency with that of a conventional runlength coding scheme.

A nonrecursive algorithm for address generating during the Hilbert scan of image buffer is presented. The technique is based on two level look-up tables. For large images, the additional storage is less than one percent of image buffer size. The present implementation of the algorithm is only about two times slower than the raster scan. Three level lool-up tables are generated if image data array is too big to fit image buffer and it is accessed from a mass storage. Software tools were developed for look-up tables generating and for the convenient use of the algorithm from C programs.

A graphic assembler language (GAL) for dealing with pictures is described with examples of its applications to computer graphics. Instruction codes of GAL are composed of four arithmetic operations of polynomials, control and input-output operations, and a sentence is defined for taking the coordinates of figures in a computer.

An extraction method of contour lines from a contour map on the market and their restoration method are described. Twin tracing points (clockwise and counterclockwise) are used to trace and extract line components from the map which involves not only contour lines but also block components such as symbols and numerals. To implement the tracing successfully, ending conditions and setting manners of the twin tracing points are dealt with taking various kinds of curves into consideration. By this method, sets of the coordinates of traced contour lines, step numbers of tracing, and moreover, the thickness and length of traced contour lines, the coordinates of their skeleton lines are obtained. Since some contour lines are cut off by the elimination of symbols and numerals, to restore them a finding method of a pair of cut off points which must be connected is also described. For the restoration, an adjacent graph is introduced with an example, and several cases of relations between a graph and set of contour lines are dealt with. A determining algorithm of a pair of connecting candidates is given. Finally, as the results, an original contour map of a mountainous area, extracted contour lines, skeleton contour lines and a connected (by straight lines) contour map obtained through the twin-tracing-points method and restoration method are illustrated.

A method is described for constructing an interpolant to a set of arbitrary data points (xi, yi), i1, 2, , n. The constructed interpolant is a piecewise parametric cubic polynomial and satisfies C1 continuity, and it reproduces all parametric polynomials of degree two or less exactly. The experiments to compare the new method with Bessel method and spline method are also shown.

A new global method for constructing a C2 piecewise quartic polynomial curve is presented. The coefficient matrix of equations which must be solved to construct the curve is tridiagonal. The joining points of adjacent curve segments are the given data points. The constructed curve reproduces exactly a polynomial of degree four or less. The results of experiments to test the efficiency of the new method are also shown.

In this paper, a new explicit transformation method between Bezier and polynomial representation is proposed. An expression is given to approximate (n + 1) Bezier control points by another of (m + 1), and to perform simple and sufficiently good approximation without any additional transformation, such as Chebyshev polynomial. A criterion of reduction is then deduced in order to know if the given number of control points of a Bezier curve is reducible without error on the curve or not. Also an error estimation is given only in terms of control points. This method, unlike previous works, is more transparent because it is given in form of explicit expressions. Finally, we discuss some applications of this method to curve-fitting, order decreasing and increasing number of control points.

Surface construction is known as a way to visualize volume data. Although currently used algorithms such as marching cubes have good enough quality for volume visualization, they do not ensure adequate surface topology. These algorithms work well when the surface is rather simple. While when complicated, the surface does not separate the internal and external spaces, that is, there exist some holes on the surface, or exist redundant overlaps or self-intersection. Actually, adequate surface topology is important not only for visualization but for laser stereolithography, which creates real 3D plastic objects. In the present paper, we propose a new method that produces a set of triangular patches from a given volume data. The fact that the set of patches has no holes, no redundancy, no self-intersection, and has orientable closed surface topology is shown.

A process of mixing viscous fluids, such as oil-based paints is applied to generate marble patterns. It is difficult to get the exact flow function of the viscous fluid, then we express the flow in terms of velocity vectors derived from simplified flow phenomena, in which the viscous liquid is supposed to be a collection of finite liquid elements. The position change of each element is calculated as the function of time and several examples of the obtained marble patterns are illustrated.

A fundamental method of producing scan animations by a digital computer is described by taking motion trajectories and lengths of light trails of objects as parameters, and examples of scan animation are illustrated.

Electrostatic drop forming characteristics of using a metal nozzle are compared with that of using glass nozzles. Taking the surface tension values of liquids as a parameter, we made experiments and concluded that the electroconductivity of liquids has prominent effects on drop formation for low surface tension liquids.

We proposed a description and coding method of Chinese characters using their structural features. In this paper, we propose a pattern generation method of Chinese characters as an application of the description and coding method. In the method, the generation process of a character can be regarded as a derivation process of sentence which expresses the character, then a Chinese character can be generated iteratively not depending on the numbers of its components and also generated in various shapes by changing some parameters needed for the generation. We can get natural shapes of characters by choosing adequate values of parameters. Many applications using this pattern generation method are considered.

A recognition method of printed Thai characters by local information of contours is described. In the method, Freeman chain code and directional differences of contour tracing of characters are utilized for eliminating contour noises and extracting concavities and convexities of characters. Each arc is then segmented by points at which the arc bends. Several local features of arcs are extracted, and are used to detect a pair of the most similar arcs between a model and an input character. Finally, the similarity between each arc pair and the similarity between characters are calculated. Further, a model making, in which a single model is generated for each category by making use of feature values of characters belonging to the same category, is described. By applying the method to 69 categories (345 data) of 5050 dots of Thai characters rotated with five kinds of arbitrary angles, a very high recognition rate has been obtained.

This paper describes a method of age-group classification of young males based on their facial images. The facial shapes of males and females are mostly formed by age 20 and 15, respectively. Our study only considered young males as they have a longer period during which facial shape is a determining factor in age estimation. Age classification was carried out using artificial neural networks. We employed 440 facial images in our experiment, composed of 4 different photographic images taken at ages 12, 15, 18 and 22 of 110 young males. Two methods of age classification were used, each employing different features extracted from the facial images, namely, "mosaic features" and "KL features. " As a result, we obtained about an 80% successful classification rate using mosaic features, and a slightly lower rate using KL features. We also analyzed the connection weights between the hidden and input layers of the trained networks, and examined facial features characteristic to each age group.

In the field of computer animation, effective methods are required, because of a large number of complicated line drawings. In this paper, an inbetweening method of animation characters is described for a mini-computer system.

A fundamental study for labeling and painting of line drawings is described, and its applications to an animation cel and alphabet are exemplified. Multiple closed regions included in binary line drawings are extracted, and they, both enclosed by image pixels and by non-image pixels, are labeled from the outermost boundary into inner boundaries. After that, a set of these labeled regions is transformed into a simple string by using inclusion relation and disjoint relation defined among them. In the method, the contour of every closed region is automatically traced, and the coordinates of the traces points are stored in the memory of a computer. Inclusion relation and disjoint relation among multiple closed regions are obtained by comparing the numbers (areas) of image pixels and non-image pixels.

As the structural information of characters and figures, features based on closed curves have been used. However, studies of feature extraction methods have been made mainly for a single closed curve. In this paper, a fundamental computer processing system is reported for dealing with very many collections of multiple closed curves which are represented by contour lines of a topographical map. Here, we describe an algorithm for obtaining every string of chain-codes which is local information of a collection of closed curves and a tree structure which is global information of the collection through one directional and a single row-by-row scan. Finally, the results obtained from the application of the proposed algorithm to simple recognition problems of mountains are described.

A recognition method of printed Thai characters by the structural analysis of their contours is described. Digital contours of characters are encoded according to directional differences of contour tracing, then, simple arithmetic operations are applied to eliminating noises and extracting concavities and convexities of the contours. Several geometric features of concave and convex arcs are used to calculate similarities of the arcs, then, a pair of the most similar arcs between a model and an input character is determined from the similarities. Finally, for recognizing characters, the similarity between each arc pair of the character portion and the similarity between characters are calculated. By applying the method to 67 categories (670 data) of Thai characters, a very high recognition rate has been obtained.