Specifies whether the convolution filter is applied to alpha as well as the color channels.

When set to false, the filter applies equally to all of the red, green, blue, and alpha channels, operating on premultiplied alpha format data.

When set to true, only the color channels are filtered, while alpha values are kept unchanged. In this case the effect will temporarily unpremultiply the red, green, and blue color component values, apply the filter kernel only to the color channels, and then re-premultiply the result.

Default value false.