SVG - Filters

SVG uses <filter> element to define filters. <filter> element uses an id attribute to uniquely identify it.Filters are defined within <def> elements and then are referenced by graphics elements by their ids.

SVG provides a rich set of filters. Following is the list of the commonly used filters.

  • feBlend
  • feColorMatrix
  • feComponentTransfer
  • feComposite
  • feConvolveMatrix
  • feDiffuseLighting
  • feDisplacementMap
  • feFlood
  • feGaussianBlur
  • feImage
  • feMerge
  • feMorphology
  • feOffset - filter for drop shadows
  • feSpecularLighting
  • feTile
  • feTurbulence
  • feDistantLight
  • fePointLight
  • feSpotLight

Declaration

Following is the syntax declaration of <filter> element. We've shown main attributes only.

<filter
   filterUnits="units to define filter effect region"
   primitiveUnits="units to define primitive filter subregion"
   
   x="x-axis co-ordinate" 
   y="y-axis co-ordinate"     
   
   width="length"
   height="length"
   
   filterRes="numbers for filter region"
   xlink:href="reference to another filter" >
</filter>

Attributes

Sr.No. Name & Description
1 filterUnits − units to define filter effect region. It specifies the coordinate system for the various length values within the filter and for the attributes defining the filter subregion. If filterUnits="userSpaceOnUse", values represent values in the current user coordinate system in place at the time when the 'filter' element is used. If filterUnits="objectBoundingBox", values represent values in fractions or percentages of the bounding box on the referencing element in place at the time when the 'filter' element is used. Default is userSpaceOnUse.
2 primitiveUnits − units to define filter effect region. It specifies the coordinate system for the various length values within the filter and for the attributes defining the filter subregion. If filterUnits="userSpaceOnUse", values represent values in the current user coordinate system in place at the time when the 'filter' element is used. If filterUnits="objectBoundingBox", values represent values in fractions or percentages of the bounding box on the referencing element in place at the time when the 'filter' element is used. Default is userSpaceOnUse.
3 x − x-axis co-ordinate of the filter bounding box. Defeault is 0.
4 y − y-axis co-ordinate of the filter bounding box. Default is 0.
5 width − width of the filter bounding box. Default is 0.
6 height − height of the filter bounding box. Default is 0.
7 filterRes − numbers representing filter regions.
8 xlink:href − used to refer to another filter.

Example

testSVG.htm 
<html>
   <title>SVG Filter</title>
   <body>
   
      <h1>Sample SVG Filter</h1>
   
      <svg width="800" height="800">
      
         <defs>
            <filter id="filter1" x="0" y="0">
               <feGaussianBlur in="SourceGraphic" stdDeviation="8" />
            </filter>
            
            <filter id="filter2" x="0" y="0" width="200%" height="200%">
               <feOffset result="offOut" in="SourceAlpha" dx="20" dy="20" />
               <feGaussianBlur result="blurOut" in="offOut" stdDeviation="10" />
               <feBlend in="SourceGraphic" in2="blurOut" mode="normal" />
            </filter>
         </defs>
         
         <g>
            <text x="30" y="50" >Using Filters (Blur Effect): </text>
            <rect x="100" y="100" width="90" height="90" stroke="green" stroke-width="3"
            fill="green" filter="url(#filter1)" />      
         </g> 
         
      </svg>
   
   </body>
</html>

  • Two <filter> elements defined as filter1 and filter2.

  • feGaussianBlur filter effect defines the blur effect with the amount of blur using stdDeviation.

  • in="SourceGraphic" defines that the effect is applicable for the entire element.

  • feOffset filter effect is used to create shadow effect. in="SourceAlpha" defines that the effect is applicable for the alpha part of RGBA graphics.

  • <rect> elements linked the filters using filter attribute.

Output

Open textSVG.htm in Chrome web browser. You can use Chrome/Firefox/Opera to view SVG image directly without any plugin. Internet Explorer 9 and higher also supports SVG image rendering.

Filter with Shadow effect

<html>
   <title>SVG Filter</title>
   <body>
      
      <h1>Sample SVG Filter</h1>
      
      <svg width="800" height="800">
      
         <defs>
            <filter id="filter1" x="0" y="0">
               <feGaussianBlur in="SourceGraphic" stdDeviation="8" />
            </filter>
            
            <filter id="filter2" x="0" y="0" width="200%" height="200%">
               <feOffset result="offOut" in="SourceAlpha" dx="20" dy="20" />
               <feGaussianBlur result="blurOut" in="offOut" stdDeviation="10" />
               <feBlend in="SourceGraphic" in2="blurOut" mode="normal" />
            </filter>
         </defs>
         
         <g>
            <text x="30" y="50" >Using Filters (Shadow Effect): </text>
            <rect x="100" y="100" width="90" height="90" stroke="green" stroke-width="3"
            fill="green" filter="url(#filter2)" />
         </g>
         
      </svg>
   
   </body>
</html>

Output

Open textSVG.htm in Chrome web browser. You can use Chrome/Firefox/Opera to view SVG image directly without any plugin. Internet Explorer 9 and higher also supports SVG image rendering.

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