创建具有 24 点或以上点阵的“新"尖刺标签

In the below diagram, the green circle is the bigger circle with radius as x and the blue circle is the smaller inner circle. By plotting points on the circles and connecting them (with lineTo commands), we get the path which is in red. When this path is filled we get the burst appearance. (Note: The inner and outer circles are only for illustration and are not drawn in the actual diagram).

• 圆上各点的X和Y坐标可以使用以下公式计算:
  • x = (圆的半径 * Cos(弧度的角度)) + 圆心的 x 坐标
  • y = (圆的半径 * Sin(弧度的角度)) + 中心的 y 坐标
  • The X and Y coordinates of each points on the circle can be calculated using the below formula:
    • x = (Radius of circle * Cos(Angle in Radians)) + x coordinate of center
    • y = (Radius of circle * Sin(Angle in Radians)) + y coordinate of center
    • 正如您和 Persijn 的答案中所使用的那样，角度计算为(360/爆发次数).使用 360 度是因为它是一个圆内的总角度.
    • 内圆上的点的角度应该在大圆上的 point1 和 point2 之间的中间，因此会添加一个增量.delta 是(360/no. of bursts)的一半

    window.onload = function() {
      var canvas = document.getElementById('canvas');
      var ctx = canvas.getContext('2d');
      var defaultBurst = 18;
      var defaultContent = "New";
    
      function paint(numBurst, text) {
        if (!numBurst) numBurst = defaultBurst;
        if (!text) text = defaultContent;
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        ctx.fillStyle = 'crimson';
        var angleInRad = Math.PI * (360 / numBurst) / 180;
        var deltaAngleInRad = angleInRad / 2;
        ctx.beginPath();
        ctx.moveTo(75, 150);
        for (i = 0; i <= numBurst; i++) {
          x1 = 75 * Math.cos(angleInRad * i) + 150;
          y1 = 75 * Math.sin(angleInRad * i) + 150;
          x2 = 60 * Math.cos((angleInRad * i) + deltaAngleInRad) + 150;
          y2 = 60 * Math.sin((angleInRad * i) + deltaAngleInRad) + 150;
          ctx.lineTo(x1, y1);
          ctx.lineTo(x2, y2);
        }
        ctx.closePath();
        /* Add shadow only for shape */
        ctx.shadowOffsetX = -5;
        ctx.shadowOffsetY = 5;
        ctx.shadowBlur = 5;
        ctx.shadowColor = "rgba(0, 0, 0, 0.5)";
        ctx.fill();
        ctx.font = "32px Arial";
        ctx.textAlign = "center";
        ctx.fillStyle = "gold";
        /* Nullify shadow for text */
        ctx.shadowOffsetX = 0;
        ctx.shadowOffsetY = 0;
        ctx.fillText(text, 150, 160, 120);
      }
      paint();
      var slider = document.getElementById('burst');
      var textInput = document.getElementById('content');
      slider.addEventListener('change', function() {
        paint(this.value, textInput.value);
      });
    
      textInput.addEventListener('blur', function() {
        paint(slider.value, this.value);
      });
    }

    /* For demo only */
    
    .controls {
      float: right;
      padding: 5px;
      margin: 50px 20px;
      line-height: 25px;
      border: 1px solid;
      box-shadow: 1px 1px 0px #222;
    }
    label,
    input {
      display: inline-block;
      vertical-align: middle;
      text-align: left;
    }
    h3 {
      padding: 10px;
      text-align: center;
    }
    label {
      width: 100px;
    }
    input[type='range'],
    input[type='text'] {
      width: 100px;
    }
    body {
      font-family: Calibri;
      background-image: radial-gradient(circle, #3F9CBA 0%, #153346 100%);
    }

    <canvas id='canvas' height='300px' width='300px'></canvas>
    <div class='controls'>
      <h3>Controls</h3>
    
      <label for="burst">Change Burst:</label>
      <input id="burst" class="slider" type="range" value="18" min="12" max="36" step='2' title="Adjust slider to increase or decrease burst" />
      <br/>
      <label for="content">Text Content:</label>
      <input type="text" id="content" maxlength="5" />
    </div>

    查看此 CodePen 以获得具有路径创建动画、阴影等功能的高级演示, 控制所有功能等.

    Check out this CodePen for an advanced demo with features like path creation animation, shadows, control over all the features etc.

    如果您想在页面的某处获得固定大小的图像，那么 Canvas 与 SVG 一样好.但是，如果您需要可以缩放到任何尺寸的图像，Canvas 不是正确的选择，因为 Canvas 是基于光栅的，并且在缩放时会变得像素化或模糊.

    If you want a fixed size image somewhere in the page then Canvas is as good as SVG. However, if you would need an image that can be scaled to any size, Canvas is not the right choice because Canvas is raster based and becomes pixelated or blurred when scaled.

    如果您的形状需要动态数量的突发和/或文本，Canvas 会比 SVG 和 CSS 更可取，因为您不必执行任何 DOM 操作.

    If your shape would need a dynamic number of bursts and/or text, Canvas would be more preferable over SVG and CSS because you don't have to perform any DOM manipulations.