折柱图--视图切换的图标设置为图片

涉及到的图片base64转码，工具链接（http://www.ab173.com/ui/image2base64.php）
参考(echarts官网中toolbox.feature. dataView/toolbox.feature. magicType)：

toolbox: {
        top: '0',
        right: '50',
        feature: {
            dataView: {
                show: true,
                readOnly: false,
                icon: 'image://file:///F:/%E7%BD%91%E9%A1%B5%E8%B5%84%E6%96%99/5suo-2/images/data.png',   
   /*   使用base64转码的方法：
 icon: 'image://data:image/png;base64,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',    */
            },
            magicType: {
                show: true,
                type: ['line', 'bar'],
                icon: {
                    line: 'image://file:///F:/%E7%BD%91%E9%A1%B5%E8%B5%84%E6%96%99/5suo-2/images/zxt.png',
                    bar: 'image://file:///F:/%E7%BD%91%E9%A1%B5%E8%B5%84%E6%96%99/5suo-2/images/zzt.png',
                },
            }
        },
    },

效果如下：