如何在不使用画布的情况下使饼图的大小固定(chart.js)

<div id="pieChartContainer"></div>

var pieChartContainer = document.getElementById('pieChartContainer');
var pieChartContext = pieChartContainer.getContext('2d');

var pieChartData = [
  { value: 30, label: 'A' },
  { value: 50, label: 'B' },
  { value: 20, label: 'C' }
];

var pieChart = new Chart(pieChartContext, {
  type: 'pie',
  data: {
    datasets: [{
      data: pieChartData.map(function(item) {
        return item.value;
      }),
      backgroundColor: ['red', 'green', 'blue']
    }],
    labels: pieChartData.map(function(item) {
      return item.label;
    })
  },
  options: {
    responsive: false
  }
});