The supplied bitmap is comverted to a new greymap. Every 1 in the originating bitmap results in a grey value of 0 (black), every 0 results in a grey value of 255 (white).
The resulting greymap is returned.
> (define bitmap (bitmap-create 640 480)) bitmap > (bitmap-equal? bitmap (greymap->bitmap (bitmap->greymap bitmap))) #t >