CSS: 100% width or height while keeping aspect ratio?

Question

Currently, with STYLE, I can use width: 100% and auto on the height (or vice versa), but I still can\'t constrain the image into a specific positio

Answer 1

I use this for a rectangular container with height and width fixed, but with images of different sizes.

img {
  max-width: 95%;
  max-height: 15em;
  width: auto !important;
}