Merge pull request #8982 from catree:morphologyEx_iterations_doc

modules/imgproc/include/opencv2/imgproc.hpp

@@ -2181,6 +2181,9 @@ kernel center.
 @param borderValue Border value in case of a constant border. The default value has a special
 meaning.
 @sa  dilate, erode, getStructuringElement
+@note The number of iterations is the number of times erosion or dilatation operation will be applied.
+For instance, an opening operation (#MORPH_OPEN) with two iterations is equivalent to apply
+successively: erode -> erode -> dilate -> dilate (and not erode -> dilate -> erode -> dilate).
  */
 CV_EXPORTS_W void morphologyEx( InputArray src, OutputArray dst,
                                 int op, InputArray kernel,