Although I haven't tested this one, I believe this should work.
var ic = $('.imageclass');
// do not touch unless you know what you're doing
var isw = ic.width();
var ish = ic.height();
var ir = isw/ish;
var ivh = $(window).height();
var sctv = ish / ivh;
ic.css('width', $(window).height() * sctv * ir);
Please change the classname of img
.imgclass in config line. If that doesn't work get back to me and I'll try to rewrite my code so it works.
P.S. You should wrap the code with `<script></script>` tags and put that in `before </body>` custom code section `:)`