Altering structuring elements from strel to suit our needs

Now, let's try to solve our first problem, which was how to create different structuring elements for each rock, using the ones generated by strel. Observing the rocks could lead to a useful conclusion, the two side rocks can be modeled as quarters of a disk and the middle rock could be modeled as half a disk. Let's see if our assumption works well for the middle rock, in the following example.