diff --git a/src/yapsut/graphics.py b/src/yapsut/graphics.py
index 133ba20970c421f44173a6d46449f72114b4d7a9..5cfebe1431cff3a38250be2453bbe47950534088 100644
--- a/src/yapsut/graphics.py
+++ b/src/yapsut/graphics.py
@@ -1,3 +1,26 @@
+import numpy as np
+class rgb_interpolator :
+   """a class to generate a 2 rgb colors interpolator """
+   @property
+   def color0(self) :
+      """the 0 color"""
+      return self._color0
+
+   @property
+   def color1(self) :
+      """the 1 color"""
+      return self._color1
+
+   def __init__(self,rgb0,rgb1) :
+      self._color0=np.array(rgb0,dtype=float)
+      self._color1=np.array(rgb1,dtype=float)
+
+   def __call__(self,x) :
+      if x <0 or x>1 :
+         raise Exception('x must be in [0,1]')
+      return self._color0*(1-x)+self._color1*x
+
+
 class ImshowXT :
    """ class to handle an improved version of plt.imshow """
    def __init__(self,matr,x_values,y_values,**kwargs) :