A run-length circle drawing algorithm with double-step

A run-length algorithm for fast circle drawing with double-step is proposed. In this algorithm, a discrete circle locus can be composed of a series of horizontal line segments and diagonal segments with slope k=-1. The algorithm can directly get the length of those line segments by performing the double-step recurrence using the errors in middle-point method and output those length in one times. The algorithm efficiency is greatly increased for 2 or more pixels can be got in each step and output operation. The drawing speed of circle is obviously faster than the speed of similar algorithms. It´s idea is simple and direct. The algorithm can finish the computation and output of a pixel in average 4.5 basic operations. The speed is raised 0.56 times compared to the Middle-Point Algorithm. The alrogithm can be spreaded to the drawing of ellipse and other quadratic curves.