title: Cases where Morphological Opening and Closing yields the same results?
body: <p>I would like to know if there are any examples or cases where Opening and Closing Morphology operations on an single image produce the same results.</p>
  
  <p>As an example, let's say we have an image <code>X</code>, and we have done opening operation to produce <code>Y</code>.  Similarly, we have done a closing operation on the original <code>X</code> to produce the same <code>Y</code>.  I would like to know if there are examples for these type of images <code>X</code>.  Programming examples in Python or MATLAB are also appreciated.</p>