柱状图颜色渐变

series: {
          name: '舆论',
          type: 'bar',
          smooth: true,
          barWidth: 10,
          data: data, 
          itemStyle: {
            normal: {
              color: function(params) {
                var colorList = [
                  ['#FFBC1B', '#FF6804'],
                  ['#67FDC6', '#00F5F5'],
                  ['#52F890', '#26A864'],
                  ['#5DA2FF', '#004CC9'],
                  ['#9882F9', '#5533E9']
                ];

                var index = params.dataIndex % colorList.length;
                // 如果是纵向的图标，则改为0, 0 , 0, 1
                return new that.$echarts.graphic.LinearGradient(1, 0, 0, 0, [
                  { offset: 0, color: colorList[index][0] },
                  { offset: 1, color: colorList[index][1] }
                ]);
              },
              barBorderRadius: 5 //柱状角成椭圆形
            }
          }
        },