ruby rails how to convert javascript to respond to

I currently got code that when I click on a button, will convert an google chart svg to image and save it. Code in the chart.erb below. What I would like to do is have rails create the image as a result of a respond to, for example localhost:3000/bdb_monitor/12345.png and in bdb_monitors_controller, have the respond_to send the png code. But I'm at a lost on how to proceed.

chart.erb function getImgData(chartContainer) { var chartArea = chartContainer.getElementsByTagName('svg')[0].parentNode; var svg = chartArea.innerHTML; var doc = chartContainer.ownerDocument; var canvas = doc.createElement('canvas'); canvas.setAttribute('width', chartArea.offsetWidth); canvas.setAttribute('height', chartArea.offsetHeight);

    canvas.setAttribute(
        'style',
        'position: absolute; ' +
        'top: ' + (-chartArea.offsetHeight * 2) + 'px;' +
        'left: ' + (-chartArea.offsetWidth * 2) + 'px;');
    doc.body.appendChild(canvas);
    canvg(canvas, svg);
    var imgData = canvas.toDataURL("image/png");
    canvas.parentNode.removeChild(canvas);
    return imgData;
  }

  function saveAsImg(chartContainer) {
    var imgData = getImgData(chartContainer);

    // Replacing the mime-type will force the browser to trigger a download
    // rather than displaying the image in the browser window.
    window.location = imgData.replace("image/png", "image/octet-stream");
  }

  function toImg(chartContainer, imgContainer) { 
    var doc = chartContainer.ownerDocument;
    var img = doc.createElement('img');
    img.src = getImgData(chartContainer);

    while (imgContainer.firstChild) {
      imgContainer.removeChild(imgContainer.firstChild);
    }
    imgContainer.appendChild(img);
  }
</script>

<%= render :partial => "shared/bdb_monitor_chart_with_save", :collection =>     BdbMonitor.overall_summary.all, :as => :bdb_monitor, :locals => {:week_ending_date =>     @week_ending_date} %>