From http://www.w3schools.com (Copyright Refsnes Data)

SVG Gaussian Blur

An SVG Filter must be defined within a <defs> tag.

Gaussian Blur

The <filter> tag is used to define an SVG filter. The <filter> tag has a required id attribute which identifies which filter will be applied to the graphic.

The <filter> tag must be nested within a <defs> tag. The <defs> tag is short for definitions and it allows definition of special elements such as filter.

Copy the following code into Notepad and save the file as "filter1.svg". Place the file in your Web directory:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg width="100%" height="100%" version="1.1"
xmlns="http://www.w3.org/2000/svg">

<defs>
<filter id="Gaussian_Blur">
<feGaussianBlur in="SourceGraphic" stdDeviation="3" />
</filter>
</defs>

<ellipse cx="200" cy="150" rx="70" ry="40"
style="fill:#ff0000;stroke:#000000;
stroke-width:2;filter:url(#Gaussian_Blur)"/>

</svg>

Code explanation:

• The id attribute of the <filter> tag defines a unique name for the filter (the same filter can be used by many elements in the document)
• The filter:url(#Gaussian_Blur) property is used to link an element to a filter. The # character must be used when linking to the filters id
• The filter effect is defined with the <feGaussianBlur> tag. The fe prefix is used for all filters
• The stdDeviation attribute of the <feGaussianBlur> tag defines the amount of the blur
• The in="SourceGraphic" part defines that the effect is created from the whole image

View example

Another example with a different stdDeviation:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg width="100%" height="100%" version="1.1"
xmlns="http://www.w3.org/2000/svg">

<defs>
<filter id="Gaussian_Blur">
<feGaussianBlur in="SourceGraphic" stdDeviation="20"/>
</filter>
</defs>

<ellipse cx="200" cy="150" rx="70" ry="40"
style="fill:#ff0000;stroke:#000000;
stroke-width:2;filter:url(#Gaussian_Blur)"/>

</svg>

View example

From http://www.w3schools.com (Copyright Refsnes Data)