如何在 amcharts 版本 4 中获取图表图像的 base 64

Question

我已经使用 amcharts 版本 4 绘制了一个简单的 amcharts 柱形图，现在我想获取图表图像的 base 64 我该怎么做？

我的图表代码

/**
 * ---------------------------------------
 * This demo was created using amCharts 4.
 * 
 * For more information visit:
 * https://www.amcharts.com/
 * 
 * Documentation is available at:
 * https://www.amcharts.com/docs/v4/
 * ---------------------------------------
 */

// Themes begin
am4core.useTheme(am4themes_animated);
// Themes end

// Create chart instance
var chart = am4core.create("chartdiv", am4charts.XYChart);

// Add data
chart.data = [{
  "country": "USA",
  "visits": 2025
}, {
  "country": "China",
  "visits": 1882
}, {
  "country": "Japan",
  "visits": 1809
}, {
  "country": "Germany",
  "visits": 1322
}, {
  "country": "UK",
  "visits": 1122
}, {
  "country": "France",
  "visits": 1114
}, {
  "country": "India",
  "visits": 984
}, {
  "country": "Spain",
  "visits": 711
}, {
  "country": "Netherlands",
  "visits": 665
}, {
  "country": "Russia",
  "visits": 580
}, {
  "country": "South Korea",
  "visits": 443
}, {
  "country": "Canada",
  "visits": 441
}, {
  "country": "Brazil",
  "visits": 395
}];

// Create axes

var categoryAxis = chart.xAxes.push(new am4charts.CategoryAxis());
categoryAxis.dataFields.category = "country";
categoryAxis.renderer.grid.template.location = 0;
categoryAxis.renderer.minGridDistance = 30;

categoryAxis.renderer.labels.template.adapter.add("dy", function(dy, target) {
  if (target.dataItem && target.dataItem.index & 2 == 2) {
    return dy + 25;
  }
  return dy;
});

var valueAxis = chart.yAxes.push(new am4charts.ValueAxis());

// Create series
var series = chart.series.push(new am4charts.ColumnSeries());
series.dataFields.valueY = "visits";
series.dataFields.categoryX = "country";
series.name = "Visits";
series.columns.template.tooltipText = "{categoryX}: [bold]{valueY}[/]";
series.columns.template.fillOpacity = .8;

var columnTemplate = series.columns.template;
columnTemplate.strokeWidth = 2;
columnTemplate.strokeOpacity = 1;

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
}

#chartdiv {
  width: 100%;
  height: 500px;
}

<script src="https://cdn.amcharts.com/lib/4/core.js"></script>
<script src="https://cdn.amcharts.com/lib/4/charts.js"></script>
<script src="https://cdn.amcharts.com/lib/4/themes/animated.js"></script>
<div id="chartdiv"></div>

我已经使用画布尝试过，但是当我将 base 64 转换为图像时，它只显示 scales 、 y-axis 和 x-axis 但不显示条形图。

我的要求是我想获得精确图像的 base 64 并将其上传到 s3 所以在第一步我需要获得 base 64 这是图表的精确图像

Answer 1

您可以使用 btoa() 和 data-url 前缀将其编码为 base 64 吗？ 尝试这个：

let svg = document.getElementsByTagName('svg')[0];
let base64 = "data:image/svg+xml;base64," + btoa(svg);