How can I fill a div with an image while keeping it proportional?

Question

If I correctly understand what you want, you may leave the width and height attributes off the image to maintain aspect ratio and use flexbox to do the centering for you.

.fill {
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden
}
.fill img {
    flex-shrink: 0;
    min-width: 100%;
    min-height: 100%
}

<div class="fill">
    <img src="https://picsum.photos/id/237/320/240" alt="" />
</div>

JSFiddle here

I tested this successfully in IE9, Chrome 31, and Opera 18. But no other browsers were tested. As always you must consider your particular support requirements.

It's a bit late but I just had the same problem and finally solved it with the help of another stackoverflow post (https://stackoverflow.com/a/29103071).

img {
   object-fit: cover;
   width: 50px;
   height: 100px;
}

Hope this still helps somebody.

Ps: Also works together with max-height, max-width, min-width and min-height css properties. It's espacially handy with using lenght units like 100% or 100vh/100vw to fill the container or the whole browser window.

All answers below have fixed width and height, which makes solution "not responsive".

To achieve the result but keep image responsive I used following:

1. Inside container place a transparent gif image with desired proportion
2. Give an image tag inline css background with image you want to resize and crop

HTML:

<div class="container">
    <img style="background-image: url("https://i.imgur.com/XOmNCwY.jpg");" src="img/blank.gif">
</div> 


.container img{
   width: 100%;
   height: auto;
   background-size: cover;
   background-repeat: no-repeat;
   background-position: center;
}​

This should do it:

img {    
min-width: 100%;
min-height: 100%;
width: auto;
height: auto;
}

An old question but deserves an update as now there is a way.

The correct CSS based answer is to use object-fit: cover, which works like background-size: cover. Positioning would be taken care of by object-position attribute, which defaults to centering.

But there is no support for it in any IE / Edge browsers, or Android < 4.4.4. Also, object-position is not supported by Safari, iOS or OSX. Polyfills do exist, object-fit-images seems to give best support.

For more details on how the property works, see CSS Tricks article on object-fit for explanation and demo.