Saving a Safari page as a PNG image
Not sure when it got added, but certainly in Safari 12 you can do this without any extensions. You need to enable the Safari Developer menu (tick in advanced settings).  Now you can select &quot;Show Web Inspector&quot; in the &quot;Develop&quot; menu which will open a window showing the page source.  Hover your cursor over the  tag and right click it. Then, select the &quot;Capture screenshot&quot; option and save when prompted.
If you only want a specific element, just right click on the appropriate bit of html.  If you are not sure, as you hover over the code the corresponding screen element is highlighted blue.
Of course, I'm now wondering if this could be apple scripted...