SVG 阴影滤镜：内发光

示例

<svg width="800px" height="600px">
<defs>
  <filter id="inner-glow">
    <feFlood flood-color="red"/>
    <feComposite in2="SourceAlpha" operator="out"/>
    <feGaussianBlur stdDeviation="2" result="blur"/>
    <feComposite operator="atop" in2="SourceGraphic"/>
</filter> 
  </defs>
  
  <text filter="url(#inner-glow)" x="30" y="100" font-size="80" font-family="Sans-Serif" font-weight="bold">SVG Filters</text>
  
</svg>