echarts 饼状图颜色渐变

series: [
          {
            name: "完成率",
            type: "pie",
            radius: ["60%", "87%"],
            avoidLabelOverlap: false,
            itemStyle :{
                normal : {
                    label : {
                        show : true,
                       position : 'center',
                        formatter : this.correctRate + "%",
                        textStyle : {
                            color : '#3D414B',
                            fontSize : '30',
                            fontFamily : '微软雅黑',
                            fontWeight : 'bold'
                        }
                    },
                    labelLine : {
                        show : false
                    }
                }
            },
            data: [
              {
                value: 100-this.correctRate,
                name: "未完成"
              },
              {
                value: this.correctRate,
                name: "完成",
                itemStyle: {
                    normal: {//颜色渐变
                        color: new echarts.graphic.LinearGradient(
                            0, 0, 0, 1,
                            [
                                {offset: 0, color: '#0095FF'},
                                {offset: 0.5, color: '#0CB9FF'},
                                {offset: 1, color: '#0095FF'}
                            ]
                        )
                    }
                }
              }
            ]
            
          }
        ],