f(x,y)=sin(sqrt((x+5)**2+(y+5)**2))*cos(8*atan2(y+5,x+5))
#      *sin(sqrt((x-5)**2+(y-5)**2))*cos(8*atan2(y-5,x-5))
#      *sin(sqrt(x**2+(y-5)**2))*cos(8*atan2(y-5,x))
#
g(x,y)= f(x,y) > 0.2 || ( f(x,y) < 0 && f(x,y) > -0.1) ? 0: 1
set pm3d map
unset colorbox 
set palette gray
set size square
unset key
unset xtics
unset ytics
set samples 512
set isosamples 512,512
set term png tiny crop
R=10
#
set out "g002.png"
splot [-R:R][-R:R] g(x,y)
#
set out "f002.png"
splot [-R:R][-R:R] f(x,y)
#
set palette color
set out "f002c.png"
splot [-R:R][-R:R] f(x,y)