Extract alpha as black & white

Hi, 

I am looking for a way to export current sequence as a only black and white fill colors, where all semi transparent (eg opacity is 50%) would be converted to black and all fully transparent pixels would be fully white (#FFFFFF), so the final output will have just two colors 

at the moment I use adjust alpha effect with invert alpha and mask only ON, it colors all alpha to white, however semi transparent parts are grey.

I was trying to use levels effects, but didn't succeed with that

Ideally I need to expand the alpha areas (white) to cover the whole frame, for this I am using Gaussian blur with maxed out blurrness. But I am looking for way to expand the white areas without gaps as the blur does

any advise?