pretty sure you're not supposed to use px in the height attribute. they are pixels.
the width will be set to match the aspect ratio but your browser will have to DL the image first. which probably doesn't matter unless you have content to the left/right of it, then it'll get bumped when the image loads. layout shift is a nasty thing.
<img src="img.png" height="100px">
(also the other parameter is set to "auto" automatically, at least in Firefox)