object-fit-cover

v1.0.4

Published

2 years ago

A polyfill for the background-image cover effect combined with responsive image behaviour with the `<img>` or `<picture>` element.

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roelfjan

object-fit responsive images srcset picture picturefill polyfill image respimg background-size: cover cover

ObjectFitCover

A polyfill for the background-image cover effect combined with responsive image behaviour with the <img> or <picture> element.

Intro

Covering an area with an image can be achieved with background-size: cover, but adding responsive image behaviour can be a pain with custom data-attributes or image-source references in CSS.

The cover effect together with responsive image behaviour can be achieved native in modern browsers (no javascript needed!) with the CSS property object-fit (support) combined with the <img> (with srcset) (support) or <picture> (support) element. ObjectFitCover adds a background-image fallback for browsers not supporting CSS property object-fit: cover. This polyfill works together with Picturefill, a polyfill for responsive image behaviour with <picture>, srcset, sizes and more.

Usage

1. Include ObjectFitCover Javascript

Preferably inline (0.6kb, 0.4kb gzipped) in the head section before the stylesheets. This to avoid flashes and have the best render performance. Copy the source from here

<head>
    <script>
      ..objectfitcover.min.js inline..
    </script>

    ...
</head>

2. Include ObjectFitCover CSS

Load it after the ObjectFitCover Javascript, to avoid flashes on the page. Preferably combined with your existing CSS.

<head>
    ...

    <link rel="stylesheet" href="objectfitcover.min.css" />
</head>

3. Include your images & CSS

.example {
    width: 100px;
    height: 300px;
}

<div class="object-fit-container cover example">
    <img src="fallback.jpg" srcset="[email protected] 1x, [email protected] 2x" />
</div>

See the examples

4. Include Picturefill

Preferably async, to avoid making it renderblocking.

<script src="picturefill.min.js" async></script>

Note: if you don't need picturefill, set window.picturefill = {} to make this polyfill work.

Browser support

object-fit: cover is supported in below browsers, so ObjectFitCover is not needed for these:

Chrome > 30
Safari > 7
Firefox > 35
Android Browser > 4.4
Opera > 18

ObjectFitCover works in:

Chrome
Safari > 3
Internet Explorer > 8
Edge
Firefox > 4
Android Browser > 2.3
Opera > 10.1

ObjectFitCover()

You can call objectFitCover() anytime to fix the image-cover in non-supporting browsers. For example with lazyloaded pictures. Option:

elements: An array of elements (parent of the actual img) that need to be fixed. The default is all .object-fit-container elements.
```
objectFitCover({
  elements: [ document.getElementsByClassname('example') ]
});
```

What is not (yet) supported?

CSS property background-attachment: fixed
CSS property object-position
Video's

What about?

Supporting all possible values of the CSS property object-fit? This polyfill can be small in size because of not supporting all possible values. The cover-effect is an often used effect on sites. It's not needed for those cases to load a complete polyfill for all possible (unused) values.

Supporting object-fit: contain? You can add this CSS to make it work as well:

.object-fit-container.contain {
    background-repeat: no-repeat;
    background-size: contain;
}
.object-fit-container.contain img {
    object-fit: contain;
}

Supporting browsers with Javascript disabled? Javascript disabled is not an issue in browsers that support object-fit: cover and <img> (with srcset) or <picture>. The image is scaled to fit the object-fitcontainer in browsers that don't support object-fit: cover. So it's not an ideal visual appearance, but it still got the image. Make sure if you use srcset to provide a fallback image in the src attribute for browsers that don't support srcset or <picture>. More info on the PictureFill website, point JS-Disabled Browsers only see alt text.