https://developers.weixin.qq.com/miniprogram/dev/devtools/minicode.html

        wx.createSelectorQuery().select('#canvas')

            .fields({

                node: true,

                size: true,

            })

            .exec((res) => {

                let canvas = res[0].node

                const width = res[0].width

                const height = res[0].height

                ctx = canvas.getContext('2d')

                const dpr = wx.getSystemInfoSync().pixelRatio

                canvas.width = width * dpr

                canvas.height = height * dpr

                ctx.scale(dpr, dpr)

                // ctx.globalAlpha(1);

                this.bigCircle(0,0);

            })

-------

        ctx.beginPath();

        ctx.arc(x, y, 130, Math.PI, 2 * Math.PI);

        ctx.lineWidth = 25;

        ctx.strokeStyle="#E5E5E5";

        ctx.stroke();

        ctx.closePath();