remove img code example, that uses concepts not present anymore

examples/code_fragments/img/modulate_image.py

-import math
-import ost.img.alg
-
-class modulator(img.RealFunction):
-    def __init__(self,f):
-        img.RealFunction.__init__(self)
-        self.f = f
-        
-    def Func(self,point):
-        return math.sin(point[0]*self.f)*math.sin(point[1]*self.f)
-
-im = img.CreateImage(img.Size(400,200))
-im.ApplyIP(img.alg.Randomize())
-
-im2 = im * modulator( 0.1 )
-
-im2.SetSpatialOrigin(img.Point(0,200))
-
-im3 = img.CreateImage(img.Size(400,400))
-im3.Paste(im)
-im3.Paste(im2)
-
-v=gui.CreateDataViewer(im3,"Modulated Image")