echarts 图表设置渐变色

从上到下

 0,0,0,1 ，上浅下深
 
 0,1,0,0，下浅上深
 
 0,0,1,0，左浅右深
 
 1,0, 0, 0, 左深右浅
 
 new echarts.graphic.LinearGradient(0, 0, 0, 1, [{
                     offset: 0,
                     color: "rgba(95,115,250,0.2)"
                 },
                 {
                     offset: 0.5,
                     color: "rgba(95,115,250,0.5)"
                 },
                 {
                     offset: 1,
                     color: "#5F73FA"
                 }
             ]),
 

option = {
  tooltip: {
    trigger: 'axis',
    axisPointer: {
      // Use axis to trigger tooltip
      type: 'shadow' // 'shadow' as default; can also be 'line' or 'shadow'
    }
  },
  legend: {},
  grid: {
    left: '3%',
    right: '4%',
    bottom: '3%',
    containLabel: true
  },
  xAxis: {
    type: 'value'
  },
  yAxis: {
    type: 'category',
    data: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
  },
  series: [
    {
      name: 'Direct',
      type: 'bar',
      stack: 'total',
      barWidth: 30,
      color: new echarts.graphic.LinearGradient(0, 0, 1, 0, [{
                    offset: 0,
                    color: "rgba(255,166,111,0.2)"
                },
                {
                    offset: 0.5,
                    color: "rgba(255,166,111,0.5)"
                },
                {
                    offset: 1,
                    color: "#FFA66F"
                }
            ]),
      label: {
        show: true,
        color: "#FFA66F"
      },
      itemStyle:{
        borderColor: 'rgba(255,166,111,0.3)',
        borderWidth: 1,
        borderRadius: [0,4,4,0]
      },
      emphasis: {
        focus: 'series'
      },
      data: [320, 302, 301, 334, 390, 330, 320]
    },
    {
      name: 'Search Engine',
      type: 'bar',
      stack: 'total',
      barWidth: 30,
      color: new echarts.graphic.LinearGradient(0, 0, 1, 0, [{
                    offset: 0,
                    color: "rgba(95,115,250,0.2)"
                },
                {
                    offset: 0.5,
                    color: "rgba(95,115,250,0.5)"
                },
                {
                    offset: 1,
                    color: "#5F73FA"
                }
            ]),
      label: {
        show: true,
        color: "#5F73FA"
      },
      itemStyle:{
        borderColor: 'rgba(95,115,250,0.3)',
        borderWidth: 1,
        borderRadius: [0,8,8,0]
      },
      emphasis: {
        focus: 'series'
      },
      data: [820, 832, 901, 934, 1290, 1330, 1320]
    }
  ]
};