ehcarts 实现 饼图扇区间隙+透明外描边

以上是UI的效果图，大致实现思路可以参考echarts官网的实例 （饼图扇区间隙）实现类似的效果。

配置如下：

option = {
  tooltip: {
    trigger: 'item'
  },
  legend: {
    top: '5%',
    left: 'center'
  },
  series: [
    {
      name: 'Access From',
      type: 'pie',
      radius: ['35%', '50%'],
      avoidLabelOverlap: false,
      padAngle: 2,
      itemStyle: {
        borderRadius: 0
      },
      label: {
        show: false,
        position: 'center'
      },
      emphasis: {
        label: {
          show: true,
          fontSize: 20,
          fontWeight: 'bold'
        }
      },
      labelLine: {
        show: false
      },
      data: [
        { value: 1048, name: 'Search Engine' },
        { value: 735, name: 'Direct' },
        { value: 580, name: 'Email' },
        { value: 484, name: 'Union Ads' },
        { value: 300, name: 'Video Ads' }
      ]
    },
    {
      name: 'Access From',
      type: 'pie',
      radius: ['50%', '55%'],
      avoidLabelOverlap: false,
      padAngle: 2,
      itemStyle: {
        borderRadius: 0,
        opacity: 0.2
      },
      label: {
        show: false,
        position: 'center'
      },
      emphasis: {
        label: {
          show: false
        }
      },
      labelLine: {
        show: false
      },
      data: [
        { value: 1048, name: 'Search Engine' },
        { value: 735, name: 'Direct' },
        { value: 580, name: 'Email' },
        { value: 484, name: 'Union Ads' },
        { value: 300, name: 'Video Ads' }
      ]
    }
  ]
};

再调整一些参数，基本上能满足UI的效果，这里不详细赘述。