Escher's Balkon : control the curvature

# Searching Escher's Balkon transform

#works for any picture

# cos amplify the curvature.

# control the curvature using the ruler

 

k1=user_float("coef 1",0,3);

k2=cos(k1*3/5);

d=H;

if(d>W) then d=W; end;

r1=2*r/d;

 

rprime=r1;

aprime=a;

if(r1<0.6) then

#rprime=-(-5+sqrt(25-40*r1))/6.666666;

rprime=-(-5+sqrt(25-40*r1))/6.67*k2/cos(k1*r1);

end;

zi=ra:[rprime*d/2,aprime];

color=origVal(zi);

color

Done