var svg = '<svg xmlns="http://www.w3.org/2000/svg" width="0.6cm" height="0.6cm"><g style="fill-opacity:0.7; stroke:black; stroke-width:0.2em;"><circle cx="0.3cm" cy="0.3cm" r="9" style="fill:yellow;" transform="translate(0,0)"/></g></svg>';
      svg = btoa(svg);

An example of circle created in javascript