我不知道只有css的解决方案。

如前所述，滤镜是在SVG中创建投影效果的规范方法。SVG规范包含了一个这样的例子。

黑色文字与白色阴影

另一种方法，我使用白色阴影(文本):创建一个克隆的阴影:

注意:这需要xmlns:xlink="http://www.w3.org/1999/xlink"在SVG声明。

真正的文本值位于<defs>节中，具有位置和样式，但没有填充定义。

文本被复制了两次:第一次用于影子，第二次用于文本本身。

<svg xmlns="http://www.w3.org/2000/svg" width="640" height="70" xmlns:xlink="http://www.w3.org/1999/xlink"> <defs> <filter id="Blur"><feGaussianBlur stdDeviation="0.8" /></filter> <text style="font-family:sans,helvetica;font-weight:bold;font-size:12pt" id="Text"><tspan x="12" y="19"> Black text with white shadow </tspan></text> </defs> <rect style="fill:#8AB" width="640" height="70" /> <use style="fill:white;" filter="url(#Blur)" xlink:href="#Text" transform="translate(1.8,.9)"/> <use style="fill:black;" xlink:href="#Text"/> </svg>

作为模糊偏差值最大的更远阴影:

<svg xmlns="http://www.w3.org/2000/svg" width="640" height="70" xmlns:xlink="http://www.w3.org/1999/xlink"> <defs> <filter id="Blur"><feGaussianBlur stdDeviation="3" /></filter> <text style="font-family:sans,helvetica;font-weight:bold;font-size:12pt" id="Text"><tspan x="12" y="19"> Black text with white shadow </tspan></text> </defs> <rect style="fill:#8AB" width="640" height="70" /> <use style="fill:white;" filter="url(#Blur)" xlink:href="#Text" transform="translate(7,5)"/> <use style="fill:black;" xlink:href="#Text"/> </svg>

您可以对常规SVG对象使用相同的方法。

同样的要求:在<defs>节没有填充定义!

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使用新的CSS过滤器属性。

webkit浏览器、Firefox 34+、Edge支持。

您可以使用这种聚合物，将支持FF < 34, IE6+。

你可以这样使用它:

/* Use -webkit- only if supporting: Chrome < 54, iOS < 9.3, Android < 4.4.4 */ .shadow { -webkit-filter: drop-shadow( 3px 3px 2px rgba(0, 0, 0, .7)); filter: drop-shadow( 3px 3px 2px rgba(0, 0, 0, .7)); /* Similar syntax to box-shadow */ } <img src="https://upload.wikimedia.org/wikipedia/commons/c/ce/Star_wars2.svg" alt="" class="shadow" width="200"> <!-- Or --> <svg class="shadow" ...> <rect x="10" y="10" width="200" height="100" fill="#bada55" /> </svg> <!-- Or --> <svg> <g fill="none" stroke="#decade" stroke-width="2" transform="scale(2)"> <circle class="shadow" cx="20" cy="20" r="19"/> <path class="shadow" d="M 20,1 V 39"/> <path class="shadow" d="M 20,1 V 20" transform="rotate(135, 20, 20)"/> <path class="shadow" d="M 20,1 V 20" transform="rotate(225, 20, 20)"/> </g> </svg>

这种方法与css的box-shadow效果不同，因为它考虑了不透明度，并且没有将阴影效果应用到框上，而是应用到svg元素本身的轮廓上。

注意:这种方法过去只在类单独放在<svg>元素上时有效。您现在可以在内联svg元素上使用它，例如<rect>。

在html5rocks上阅读更多关于css过滤器的内容。

下面是一个使用'filter'属性为svg应用dropshadow的例子。如果你想控制投影的不透明度，看看这个例子。slope属性控制投影的不透明度。

相关的例子:

<filter id="dropshadow" height="130%">
  <feGaussianBlur in="SourceAlpha" stdDeviation="3"/> <!-- stdDeviation is how much to blur -->
  <feOffset dx="2" dy="2" result="offsetblur"/> <!-- how much to offset -->
  <feComponentTransfer>
    <feFuncA type="linear" slope="0.5"/> <!-- slope is the opacity of the shadow -->
  </feComponentTransfer>
  <feMerge> 
    <feMergeNode/> <!-- this contains the offset blurred image -->
    <feMergeNode in="SourceGraphic"/> <!-- this contains the element that the filter is applied to -->
  </feMerge>
</filter>
<circle r="10" style="filter:url(#dropshadow)"/>

Box-shadow被定义为用于CSS框(阅读:矩形)，而svg比矩形更有表现力。阅读SVG入门教程，了解更多关于SVG过滤器的功能。

我不知道只有css的解决方案。

如前所述，滤镜是在SVG中创建投影效果的规范方法。SVG规范包含了一个这样的例子。

可能是一种进化，看起来内联css过滤器在元素上工作得很好，在某种程度上。

如前所述，在svg元素中，在类中或内联中声明投影css过滤器是无效的。

但是，至少在Firefox中，使用以下魔法:

在DOM加载后，用javascript内联添加过滤器声明。

// Does not works, with regular dynamic css styling: shadow0.oninput = () => { rect1.style.filter = "filter:drop-shadow(0 0 " + shadow0.value + "rem black);" } // Okay! Inline styling, appending. shadow1.oninput = () => { rect1.style += " ;filter:drop-shadow(0 0 " + shadow1.value + "rem black);" rect2.style += " ;filter:drop-shadow(0 0 " + shadow1.value + "rem black);" } <h2>Firefox only</h2> <h4> Does not works! <input id="shadow0" type="number" min="0" max="100" step="0.1"> | Okay! <input id="shadow1" type="number" min="0" max="100" step="0.1"> <svg viewBox="0 0 120 70"> <rect id="rect1" x="10" y="10" width="100" height="50" fill="#c66" /> <!-- Inline style declaration does NOT works at svg level, no shadow at loading: --> <rect id="rect2" x="40" y="30" width="10" height="10" fill="#aaa" style="filter:drop-shadow(0 0 20rem black)" /> </svg>