[WPF] Fix high-DPI image scaling
[WPF] Fix high-DPI image scaling

This should fix issue #401.

iainx/xwt,mminns/xwt,cra0zy/xwt,directhex/xwt,akrisiun/xwt,mono/xwt,sevoku/xwt,lytico/xwt,steffenWi/xwt,hamekoz/xwt,TheBrainTech/xwt,mminns/xwt,hwthomas/xwt,antmicro/xwt,residuum/xwt