Treehouse

Spoiler Prevention with CSS Filters

By on  
CSS Filter

No one likes a spoiler.  Whether it be an image from an upcoming film or the result of a football match you DVR'd, sometimes you just don't want to know.  As a possible provider of spoiler content, some sites may choose to warn users ahead of time.  Sometimes the article title is prefixed with [SPOILER] text or a something similar.  I've thought of a better way -- use CSS filters to blur spoiler content.

The CSS

CSS filters provide a simple way to blur the spoiler content so that the underlying image or text is not legible:

.spoiler {
	-webkit-filter: blur(20px);
	-webkit-transition-property: -webkit-filter;
	-webkit-transition-duration: .4s;
}
.spoiler:hover, .spoiler:focus {
	-webkit-filter: blur(0px);
}

You will also note that hovering over the offending content will animate the blur until it's been removed.  Unfortunately CSS filters are only supported in WebKit at the moment, but we can no doubt expect more browser support shortly. Also note the :focus addition -- if you set tabIndex=0 on all .spoiler elements, you can support mobile touch to unblur as well!

This jQuery plugin tipped me off on how to achieve a similar blur within Firefox using SVG:

<img src="ricci.jpg" alt="Christina Ricci" class="spoiler" style="filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'blur\'><feGaussianBlur stdDeviation=\'20\' /></filter></svg>#blur");" />

Not the most beautiful of code but works nonetheless.  Changing the stdDeviation to 0 (via JavaScript) would present the element without blur.

Preventing spoiler content is a very limited case (even more limited in the case the photo is Christina Ricci) but it's good to have a strategy just in case.  I like this strategy because it provides an easy option to the user (hovering) to view the obscured content.

ydkjs-4.png

Recent Features

  • Vibration API

    Many of the new APIs provided to us by browser vendors are more targeted toward the mobile user than the desktop user.  One of those simple APIs the Vibration API.  The Vibration API allows developers to direct the device, using JavaScript, to vibrate in...

  • 9 More Mind-Blowing WebGL Demos

    With Firefox OS, asm.js, and the push for browser performance improvements, canvas and WebGL technologies are opening a world of possibilities.  I featured 9 Mind-Blowing Canvas Demos and then took it up a level with 9 Mind-Blowing WebGL Demos, but I want to outdo...

Incredible Demos

  • Parallax Sound Waves Animating on Scroll

    Scrolling animations are fun. They are fun to create and fun to use. If you are tired of bootstrapping you might find playing with scrolling animations as a nice juicy refreshment in your dry front-end development career. Let's have a look how to create animating...

  • Upload Photos to Flickr with PHP

    I have a bit of an obsession with uploading photos to different services thanks to Instagram. Instagram's iPhone app allows me to take photos and quickly filter them; once photo tinkering is complete, I can upload the photo to Instagram, Twitter, Facebook, and...

Discussion

  1. I was actually going to write about this but my only issue is it’s a little buggy in that when you hover over the image initially it the blur radius might change, and then on mouse out the blur will not exceed the limits of the image. It’s a beautiful effect but unfortunately the implementation is not quite there.

  2. Yeah, I like the effect. I did something similar quite a while ago using the text-shadow property to create a “blurry” kind of overlay (http://devseo.co.uk/blog/view/blurry-text-simple-snapshots-with-html-css3) this is a lot more effective, but I don’t like the way it “pops” at the end of the animation before completing the “faded” animation

  3. Very cool but only works in Chrome for me. No dice in Firefox nor IE10.

    Thanks.

    • As the post mentions, this is WebKit-only until Firefox and IE implement CSS filters.

  4. Thanks for the svg filter code. This looks like it could be handy for lots of things. Like Lea Verou’s blurred background behind a semitransparent text–background overlay, over a background image.

  5. The blurr effect is much similar with the “fade effect” like here: http://theweeblytricks.weebly.com/3.html

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!