k4 attribute defines one of the value to be used within the the
arithmetic operation of the
<feComposite> filter primitive. If this attribute is not set, its default value is 0.
The pixel composition is computed using the following formula:
result = k1*i1*i2 + k2*i1 + k3*i2 + k4
|Normative document||SVG 1.1 (2nd Edition)|
The following elements can use the