sharpness recombination

#mpeg2source()

vs=blur(1,0)
hs=blur(0,1)

vb=vs.blur(0,1)

sub=subtract(vs,vb)
hs.subtract(sub.invert)
a=last

hb=hs.blur(1,0)

sub=subtract(hs,hb)
vs.subtract(sub.invert)

merge(a)