Basic Raster Graphics Algorithm For Drawing Primitives

In nowadays, the use of graphics technology is more and more used in computer applications. With the using of graphics technology increasingly extensive, the study of computer graphics becomes more and more important. Currently, the widely used graphic display is raster-scanning display. Therefore, raster graphics algorithm is the basis of computer graphics. Straight line, arc, ellipse are the basic graphic elements, so the algorithm for generating these graphics is effect the efficiency of the graphics system directly, and therefore, the quicker the basic graphics generated, the quicker the graphic system is.At present, a large number of domestic and foreign scholars have focused their attention on the algorithm of generate of the circle, therefore, the algorithm has been more perfect for the arc generation. The current algorithms for generating arc are Pluses and Minuses method, Bresenham algorithm, Midpoint algorithm and Polygon Approximation method. In addition, the double-step algorithm, and the level linear based scan conversion algorithm, Fast Algorithm for the Drawing of Circles are algorithms draw serial points each time. However, the study of the elliptical algorithm mapping remains in a homo-point level. Thinking that ellipse is rather universal than the arc, any progress in the algorithm of generate ellipse is very important, however, it also has great difficulty.The homo-point method is an algorithm for generating only one pixel for each step, in other words, all the pixels are generated with a painting-by-point order. In a practical application, the time for output the location of the points is far more than the calculation of the computer used, that is to say, if reduce the time of output operation will reduce the time of the algorithm. And outputting serial points with some common features at each time is the direct method. The ellipse can be viewed as a series of discrete elliptical orbit with the same y coordinates of the horizontal line and a series of adjacent pixels with the same x coordinate of the vertical line of pixels and the di- agonal sections of the slope of -1. Using this feature, this thesis put a more efficient method of drawing an oval.Based on the deep analysis and research of the discrete elliptical orbit, this thesis put a quick algorithm for drawing ellipse. Using the features of the discrete elliptical orbit, the new algorithm finds every horizontal line and vertical lines first, then drawing them. Each implementation of the new algorithm can be generate at list 2 points, so the new algorithm greatly reduce the time of the output operation, then make the ellipse generation more efficient.In the same accuracy, the new algorithm is more advantaged than the traditional oval rendering algorithm, just like Midpoint algorithm. The experimental results show that the new algorithm can drawing ellipse 2 times quicker than the traditional oval rendering algorithm.Ellipse is a universal quadratic curve, and quadratic curves, just like hyperbola and parabola, are composed by series of horizontal lines and vertical lines and the diagonal lines too. So I want use the method of this paper to generate other quadratic curves for the future research, and I believe it will be a meaningful job.