Procedural generation of polygon collider

Hi everyone!

Today, I've got just one wuite simple question... Is it possible to somehow change a polygon collider of sprites in the code?
I'm discarding some pixels of a sprite with my shader and I need the polygon collider to be kinda more perfect. Is it possible to proceduraly chnge the polygon collider depending on alpha?

Thanks for any feedback... And please, excuse my English...
Have a nice day!