-- noise addition in CIE Lab color space

amount = 40  -- amount of noise

for y = 0, height-1 do
    for x = 0, width-1 do
      l,a,b = get_lab (x,y)
             
      random=(math.random()-0.5)*amount
      l=l+random
      a=a+random
      b=b+random

      set_lab (x,y, l, a, b)
    end
    progress(y/height)
end