[[File:sf-hwc-2016-06-15.jpg]] should just resize with the window and never overflow:
And here's a test of class= option, e.g. [[File:sf-hwc-2016-06-15.jpg|class=u-photo]]
Which only causes alt="class=u-photo" :(
Testing [[File:sf-hwc-2016-06-15.jpg|" class="u-photo]] doesn't work either, and causes escaped quotes: alt="" class="u-photo"