LayoutTests/svg/filters/feMerge.svg

<svg xmlns="http://www.w3.org/2000/svg">
<defs>
<filter id="filter_1" primitiveUnits="objectBoundingBox">
<feFlood x="0" y="0" width="50%" height="100%" flood-color="rgb(255,0,0)" result="input1"/>
<feFlood x="40%" y="0" width="60%" height="100%" flood-color="rgb(0,0,255)" result="input2"/>
<feMerge>
<feMergeNode in="input1"/>
<feMergeNode in="input2"/>
</feMerge>
</filter>

<filter id="filter_2" primitiveUnits="objectBoundingBox">
<feFlood flood-color="rgb(255,0,0)" result="input1"/>
<feFlood x="-40%" y="30%" width="110%" height="150%" flood-color="rgb(0,0,255)" result="input2"/>
<feMerge>
<feMergeNode in="input1"/>
<feMergeNode in="input2"/>
</feMerge>
</filter>

<filter id="filter_3" primitiveUnits="objectBoundingBox">
<feFlood x="10%" y="10%" width="50%" height="50%" flood-color="rgb(255,0,0)" result="input1"/>
<feFlood x="30%" y="30%" width="50%" height="50%" flood-color="rgb(0,0,255)" result="input2"/>
<feMerge>
<feMergeNode in="input1"/>
<feMergeNode in="input2"/>
</feMerge>
</filter>
</defs>

<rect x="10" y="10" width="150" height="150" filter="url(#filter_1)" />
<rect x="210" y="10" width="150" height="150" filter="url(#filter_2)" />
<rect x="410" y="10" width="150" height="150" filter="url(#filter_3)" />
</svg>