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.