markerUnits markerWidth markerHeight 的替代值的影响

绘图标记的默认设置是使用调用元素的笔触宽度，但你可以通过指定 markerUnits="userSpaceOnUse" 显式指定使用单位系统绘制标记所应用元素的标记。标记被绘制到 3x3 markerUnits 框中（如果未指定 markerUnits，则为 3 个笔划宽度）。但是可以使用 markerHeight 和 markerWidth 明确指定框的宽度和高度。请参阅下文，了解 markerUnits，markerHeight 和 markerWidth 的各种组合的效果。

<svg width="800px" height="600px">
<defs>
      <marker id="marker1"
      viewBox="0 0 10 10" refX="0" refY="5" orient="auto" markerUnits="strokeWidth" markerWidth="1" markerHeight="1">
      <path d="M 0 0 L 10 5 L 0 10 z" />
                                     </marker>
      <marker id="marker2"
      viewBox="0 0 10 10" refX="0" refY="5" orient="auto" markerUnits="strokeWidth" markerWidth="4" markerHeight="4">
      <path d="M 0 0 L 10 5 L 0 10 z" />
                                     </marker>
      <marker id="marker3"
      viewBox="0 0 10 10" refX="0" refY="5" orient="auto" markerUnits="userSpaceOnUse" markerWidth="15" markerHeight="15">
      <path d="M 0 0 L 10 5 L 0 10 z" />
                                     </marker>
      <marker id="marker4"
      viewBox="0 0 10 10" refX="0" refY="5" orient="auto" markerUnits="userSpaceOnUse" markerWidth="30" markerHeight="30">
      <path d="M 0 0 L 10 5 L 0 10 z" />
                                     </marker>
  </defs>
  
  <line  x1="20" y1="20" x2="100" y2="100" stroke-width="8" stroke="blue" marker-end="url(#marker1)" />     
    <text x="20" y="150"> markerUnits = strokeWidth </text>
    <text x="20" y="170"> markerWidth|Height = 1 </text>
  
  <line  x1="220" y1="20" x2="300" y2="100" stroke-width="8" stroke="blue" marker-end="url(#marker2)" />      
    <text x="250" y="150"> markerUnits = strokeWidth </text>
    <text x="250" y="170"> markerWidth|Height = 4 </text>
  
  <line  x1="20" y1="220" x2="100" y2="300" stroke-width="8" stroke="blue" marker-end="url(#marker3)" />      
      <text x="20" y="390"> markerUnits = userSpaceOnUse </text>
      <text x="20" y="410"> markerWidth|Height = 15 </text>
  
  <line  x1="220" y1="220" x2="300" y2="300" stroke-width="8" stroke="blue" marker-end="url(#marker4)" />      
      <text x="250" y="390"> markerUnits = userSpaceOnUse </text>
      <text x="250" y="410"> markerWidth|Height = 30 </text>
</svg>