Inkscape - Vintage Colour effects

import coloreffect
import math

class C(coloreffect.ColorEffect):
  def colmod(self,r,g,b):
    r = float(r) / 255
    g = float(g) / 255
    b = float(b) / 255
    r = r * 0.75 + g * 0.25
    g = g * 0.75 + b * 0.25
    b = b * 0.75 + b * 0.25
    r = int(r * 255)
    g = int(g * 255)
    b = int(b * 255)
    return '%02x%02x%02x' % (r,g,b)

c = C()
c.affect()