What I was thinking of doing is creating
new cover images for epubs with the actual pixel dimensions 800 x 1200 and use the svg wrapper on those (in place of fixed 600 x 800 I was making). I didn't mean - though probably didn't make clear - that I would use the 3/4 ratio on existing images that aren't exactly that ratio.
So, would the following code be what I am after?
Code:
<div>
<svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="xMidYMid meet" version="1.1" viewBox="0 0 800 1200" width="100%" xmlns:xlink="http://www.w3.org/1999/xlink">
<image height="1200" width="800" xlink:href="../Images/cover.jpg"></image>
</svg>
</div>
And just going slightly off topic, I stopped using "height=" and "width=" attributes with images a while back because I thought they were deprecated. Would I be better to give the cover image a class and use "img {width: xxx; height: xxx;}"? Ditto for the svg tag?