This SVG example illustrates how to apply a gaussian blur filter.

BlurFilter.svg

<svg width="400" height="200" xmlns="http://www.w3.org/2000/svg">
  <filter id="idBlurFilter">
    <feGaussianBlur stdDeviation="4"/> 
  </filter>
  <!-- Original Version -->
  <circle cx="100" cy="100" r="75" fill="black" stroke="red" stroke-width="10"></circle>
  <!-- Filtered Version -->
  <g style="filter: url(#idBlurFilter)" transform="translate(200, 0)">
    <circle cx="100" cy="100" r="75" fill="black" stroke="red" stroke-width="10"></circle>
  </g>
</svg>

Output