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.

A recognition method of handprinted Thai characters by using local features is described. In the method, Freeman chain code and directional differences of contour tracing are utilized for extracting concavities and convexities of characters. Several local features are used to calculate similarities between arc portions and similarity between characters. Similar arcs are detected from characters of different categories to make a dictionary of arcs. Then, a dictionary of characters containing lists of names of character arcs is made to obtain a compact dictionary of models. By applying the method to 69 categories (828 data) of Thai characters, a recognition rate of 99.3% for learning data, and a recognition rate of 88.9% for test data have been obtained.

This paper reports an on-line recognition method of Thai characters being composed of curves, and having many complicated and similar shapes. A character stroke is segmented into clockwise and counter clockwise arcs according as the stroke tracing is clockwise or counter clockwise, by making use of eight directional codes and directional differences of stroke tracing. Intuitively described features such as the sequence of stroke arcs, types of arc and relative positions of arcs are utilized for classifying characters. A multi-step classification method is introduced to achieve a good recognition rate. By applying the method to 69 categories (414 data) of Thai characters, a recognition rate of 100% for learning data, and a recognition rate of 96.4% for test data have been obtained.

The sequence of 8-point DCT and scalar quantization is effective in image data compression. The operation is executed very efficiently, if the DCT coefficients need not to be found explicitly. The present paper proposes a method, requiring only five times of multiplication for the transform. The 8-point DCT can be comopsed from the 16-point DFT which gives only the real parts of coefficients, and final scaling. The real part DFT can be implemented by the small FFT Winograd algorithm, which requires only five multiplications. The final scaling can be combined with the quantizing matrix without any change in arithmetic complexity of the qunatizer. Since each signal path in the proposed algorithm has one multiplication at most, the five multiplications can be executed in parallel. This will make the hardware implementation of the algorithm effective.

This paper presents an image compression coding sheme named Boundary Detection Coding (BDC). It is worked out to compress digital multi-color images having large uniformly colored areas. Input images to the BDC encoder are given in the raster scan data format. The encoder detects boundary points of uniformly colored areas and changes them into compression codes. It does not generate any code while scanning uniformly colored areas. The BDC decoder changes the boundary codes back to the original image using some characteristics of boundary points. The BDC is much more efficient than the one-dimensional runlenght coding method. This paper covers the coding algorithm of the BDC, the results of some experiments and comparison with other methods.

A method of motion segmentation in RGB image sequences is presented in details. The method is based on moving object modeling by a six-variate Gaussian distribution and a hidden Markov random field (MRF) framework. It is an extended and improved version of our previous work. Based on mathematical principles the energy expression of MRF is modified. Moreover, an initialization procedure for the first frame of the sequence is introduced. Both modifications result in new interesting features. The first involves a rather simple parameter estimation which has to be performed before the use of the method. Now, the values of Maximum Likelihood (ML) estimators of the parameters can be used without any user's modifications. The last allows one to avoid finding manually the localization mask of moving object in the first frame. Experimental results showing the usefulness of the method are also included.

Based on appearing frequencies of directional changes in contour line tracing, a chain coding method using three directional differences is described. Smoothed contour lines and 2-3 bit-compression compared with Freeman's chain code are obtained applying the method on 20 contour lines of lakes.

A new method for interpolating boundary function values and first derivatives of a triangle is presented. This method has a relatively simple construction and involves no compatibility constraints. The polynomial precision set of the interpolation function constructed includes all the cubic polynomial and less. The testing results show that the surface produced by the proposed method is better than the ones by weighted combination schemes in both of the fairness and preciseness.