阴影滤镜基本 Dropshadow

<svg width="800px" height="600px">
<defs>
  <filter id="drop-shadow">
    <feGaussianBlur in="SourceAlpha" stdDeviation="4"/>
    <feOffset dx="5" dy="5" result="offsetblur"/>
    <feFlood flood-color="red"/>
    <feComposite in2="offsetblur" operator="in"/>
    <feMerge>
      <feMergeNode/>
      <feMergeNode in="SourceGraphic"/>
  </feMerge>
</filter> 
  </defs>
  
  <text filter="url(#drop-shadow)" x="30" y="100" font-size="80">SVG Filters</text>
  
</svg>