const query = wx.createSelectorQuery()
        query.select('#canvas')
            .fields({
                node: true,
                size: true
            })
            .exec((res) => {
                const canvas = res[0].node
                canvas.width = 20;
                canvas.height = 256;
                let ctx = canvas.getContext("2d");
                const colorStops = {
                    0: "blue",
                    0.5: "yellow",
                    1: "red",
                };
                // 创建线性渐变色
                let linearGradient = ctx.createLinearGradient(0, 0, 0, canvas.height);
                console.log(colorStops);
                for (const key in colorStops) {
                    linearGradient.addColorStop(key, colorStops[key]);
                }
                // 绘制渐变色条
                ctx.fillStyle = linearGradient;
                ctx.fillRect(0, 0, canvas.width, canvas.height);
            })