EChart 如何直接调用saveAsImageecharts 柱状配置项内容和展示

请问我如何直接在后台调用saveAsImage，因为项目需要储存报表数据，顺便保存一张图片作为前台粗略展示

      option = {
    title: {
        text: 'ECharts 入门示例'
    },
    tooltip: {},
    legend: {
        data:['销量']
    },
    toolbox : {
      show:true,
      feature :{
          saveAsImage:{
              type: 'png'
          }
      }
    },
    xAxis: {
        data: ["衬衫","羊毛衫","雪纺衫","裤子","高跟鞋","袜子"]
    },
    yAxis: {},
    series: [{
        name: '销量',
        type: 'bar',
        data: [5, 20, 36, 10, 10, 20]
    }]
};