I would like my images to stretch to 100% of their container div, and that container div is set to width: 90%. I wanted to do this with CSS (I avoid javascript when I can) but I see that printDefaultSizedImage includes width="900" height="562" and I don't see a way of turning it off.
As a side-note, I upload images 1920px wide or larger, so in most cases "stretch" will mean downscaling them to 90% of the user's viewport, so they should still be sharp.
What is the recommended way of stretching images proportionally to fit the width of the container div?