CSS – How to Fill Image Size Without Stretching

Yes you need an encapsulating div:

<div id="logo"><img src="logo.jpg"></div>

with something like:

#logo { height: 100px; width: 200px; overflow: hidden; }

Other solutions (padding, margin) are more tedious (in that you need to calculate the right value based on the image's dimensions) but also don't effectively allow the container to be smaller than the image.

Also, the above can be adapted much more easily for different layouts. For example, if you want the image at the bottom right:

#logo { position: relative; height: 100px; width: 200px; }
#logo img { position: absolute; right: 0; bottom: 0; }

Auto-sizing Images to Fit a Div - Making the CSS Work

Here is one way of doing it, start with the following HTML:

<div class="container portrait">
    <h4>Portrait Style</h4>
    <img src="http://placekitten.com/150/300">
</div>

and the CSS:

.container {
    height: 300px;
    width: 240px;
    background-color: red;
    float: left;
    overflow: hidden;
    margin: 20px;
}
.container img {
    display: block;
}

.portrait img {
    width: 100%;
}
.landscape img {
    height: 100%;
}

and the demo fiddle: http://jsfiddle.net/audetwebdesign/QEpJH/

When you have an image oriented as a portrait, you need to scale the width to 100%. Conversely, when the image is landscape oriented, you need to scale the height.

Unfortunately, there is no combination of selectors in CSS that targets the aspect ratio of the image, so you can't use CSS to pick out the correct scaling.

In addition, you have no easy way of centering the image since the top left corner of the image is pinned to the top left corner of the containing block.

jQuery Helper

You can use the following jQuery action to determine which class to set based on the aspect ratio of the image.

$(".container").each(function(){
    // Uncomment the following if you need to make this dynamic
    //var refH = $(this).height();
    //var refW = $(this).width();
    //var refRatio = refW/refH;

    // Hard coded value...
    var refRatio = 240/300;

    var imgH = $(this).children("img").height();
    var imgW = $(this).children("img").width();

    if ( (imgW/imgH) < refRatio ) { 
        $(this).addClass("portrait");
    } else {
        $(this).addClass("landscape");
    }
})

For each image in .container, get the height and width, test if width<height and then set the appropriate class.

Also, I added a check to take into account the aspect ratio of the containing block. Before, I had implicitly assumed a square view panel.