javascript - 使用 Chart js 插件创建类似圆环图的圆弧

Question

我正在尝试创建一个如下图所示的图表。

到目前为止，我设法通过圆环图获得显示在中心的值，但不是像图表那样的弧形。这是我的代码

Chart.pluginService.register({
  beforeDraw: function(chart) {
    var width = chart.chart.width,
      height = chart.chart.height,
      ctx = chart.chart.ctx

    ctx.restore()
    var fontSize = (height / 114).toFixed(2)
    ctx.font = fontSize + 'em sans-serif'
    ctx.textBaseline = 'middle'

    var text = chart.config.data.text,
      textX = Math.round((width - ctx.measureText(text).width) / 2),
      textY = height / 2

    ctx.fillText(text, textX, textY)
    ctx.save()
  },
})

关于如何实现这一点有什么想法吗？

Answer 1

你可能想在 options 对象中rotation, circumference:

var ctx = document.getElementById("myChart");
var myChart = new Chart(ctx, {
  type: 'doughnut',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
      label: '# of Votes',
      data: [12, 19, 3, 5, 2, 3],
      backgroundColor: [
        'rgba(255, 99, 132, 0.2)',
        'rgba(54, 162, 235, 0.2)',
        'rgba(255, 206, 86, 0.2)',
        'rgba(75, 192, 192, 0.2)',
        'rgba(153, 102, 255, 0.2)',
        'rgba(255, 159, 64, 0.2)'
      ],
      borderColor: [
        'rgba(255,99,132,1)',
        'rgba(54, 162, 235, 1)',
        'rgba(255, 206, 86, 1)',
        'rgba(75, 192, 192, 1)',
        'rgba(153, 102, 255, 1)',
        'rgba(255, 159, 64, 1)'
      ],
      borderWidth: 1
    }]
  },
  options: {
    rotation: 1 * Math.PI,
    circumference: 1 * Math.PI
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.8.0/Chart.bundle.js"></script>
<div id="canvas-holder" style="width:40%">
  <canvas id="myChart" width="533" height="266" class="my-chart">
         </canvas>
</div>
<style>
  canvas {
    -moz-user-select: none;
    -webkit-user-select: none;
    -ms-user-select: none;
  }
  
  .my-chart {
    display: block;
    width: 533px;
    height: 266px;
  }
</style>