

QuadraticCurvewTo中x1,y1就是起点,x2,y2就是终点
html5quadratic
QuadraticCurveTo:
http://tinyurl.com/html5quadratic
QuadraticCurveTo
quadraticCurveTo绘制贝塞尔曲线
二次贝塞尔曲线,(x0, y0)就是曲线的起始点,(x2, y2)就是曲线的终止点
arcTo
canvas 绘制贝塞尔曲线!