SVG to PNG in javascript

I have a problem with converting svg to png(base64). Svg to base64 works fine, because it displays just fine in the browser. But when i try to load in the image, it won't load. Anybody might have an idea why?

  var xml = new XMLSerializer().serializeToString(svg);
  var svg64 = btoa(xml);
  var b64start = 'data:image/svg+xml;base64,';
  var image64 = b64start + svg64;
  console.log(image64);

  const img = new Image();

  img.onload = function() {
    const canvas = document.createElement('canvas');
    canvas.width = img.width;
    canvas.height = img.height;
    const ctx = canvas.getContext('2d');
    ctx.drawImage(img, 0, 0);
    const dataBase64 = canvas.toDataURL('image/png');
    console.log(dataBase64);

    generatePowerpoint(response, dataBase64);
  }
  img.onerror = function() {
    console.log(this.src);

  }
  img.src = image64;