arc()
https://developers.weixin.qq.com/miniprogram/dev/api/canvas/CanvasContext.arcTo.html
CanvasContext.arcTo(number x1, number y1, number x2, number y2, number radius)
这个x2是圆的半径吧??
y2是起始弧度吧??
https://developers.weixin.qq.com/miniprogram/dev/api/canvas/CanvasContext.arcTo.html
这个x2是圆的半径吧??
y2是起始弧度吧??