echarts 折现区域填充渐变色

option = {
    title: {
        text: '',
        subtext: ''
    },
    tooltip: {
        trigger: 'axis'
    },
    legend: {
        data:[]
    },
    
    xAxis:  {
        type: 'category',
        boundaryGap: false,
        data: ['周一','周二','周三','周四','周五','周六','周日']
    },
    yAxis: {
        type: 'value',
        axisLabel: {
            formatter: '{value} °C'
        }
    },
    series: [
        {
            name:'',
            type:'line',
            data:[11, 2, 15, 7, 12, 12, 6],
            markPoint: {
                data: [
                    {type: 'max', name: '最大值'},
                    {type: 'min', name: '最小值'}
                ]
            },
            markLine: {
                data: [
                    {type: 'average', name: '平均值'}
                ]
            },
            itemStyle: {
                normal: {
                    color: '#00c1de',
                    shadowBlur: 8,
                    shadowColor: '#25d5f0',
                    borderColor:'#00c1de',
                    borderWidth:2,
                    backgroundColor:'transparent'
                }
            },
            areaStyle: {normal: {
                color: new echarts.graphic.LinearGradient(0, 0, 0, 1, [{
                        offset: 0,
                        color: '#00c1de'
                    }, {
                        offset: 1,
                        color: 'rgba(0,0,0,0)'
                    }]),
            }}
        }
    ]
};