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>