Add images for tutorials on morphological operations to avoid possible confusion.

doc/tutorials/imgproc/erosion_dilatation/erosion_dilatation.rst

@@ -53,6 +53,14 @@ Dilation
 
 The background (bright) dilates around the black regions of the letter.
 
+To better grasp the idea and avoid possible confusion, in this another example we have inverted the original image such as the object in white is now the letter. We have performed two dilatations with a rectangular structuring element of size :math:`3x3`.
+
+  .. image:: images/Morphology_1_Tutorial_Theory_Dilatation_2.png
+     :alt: Left image: original image inverted, right image: resulting dilatation
+     :align: center
+
+The dilatation makes the object in white bigger.
+
 Erosion
 ^^^^^^^^
 
@@ -66,6 +74,13 @@ Erosion
      :alt: Erosion result - Theory example
      :align: center
 
+In the same manner, the corresponding image resulting of the erosion operation on the inverted original image (two erosions with a rectangular structuring element of size :math:`3x3`.
+
+  .. image:: images/Morphology_1_Tutorial_Theory_Erosion_2.png
+     :alt: Left image: original image inverted, right image: resulting erosion
+     :align: center
+
+The erosion makes the object in white smaller.
 
 Code
 ======

doc/tutorials/imgproc/opening_closing_hats/opening_closing_hats.rst

@@ -31,7 +31,7 @@ In the previous tutorial we covered two basic Morphology operations:
    * Erosion
    * Dilation.
 
-Based on these two we can effectuate more sophisticated transformations to our images. Here we discuss briefly 05 operations offered by OpenCV:
+Based on these two we can effectuate more sophisticated transformations to our images. Here we discuss briefly 5 operations offered by OpenCV:
 
 Opening
 ---------
@@ -50,6 +50,12 @@ Opening
      :alt: Opening
      :align: center
 
+For the sake of clarity, we have performed the opening operation (:math:`7x7` rectangular structuring element) on the same original image but inverted such as the object in white is now the letter.
+
+  .. image:: images/Morphology_2_Tutorial_Theory_Opening_2.png
+     :alt: Left image: original image inverted, right image: resulting opening
+     :align: center
+
 Closing
 ---------
 
@@ -65,6 +71,11 @@ Closing
      :alt: Closing example
      :align: center
 
+On the inverted image, we have performed the closing operation (:math:`7x7` rectangular structuring element):
+
+  .. image:: images/Morphology_2_Tutorial_Theory_Closing_2.png
+     :alt: Left image: original image inverted, right image: resulting closing
+     :align: center
 
 Morphological Gradient
 ------------------------