7 posts on CSS Images

Important -prefix-free update

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Those of you that have been following and/or using my work, are surely familiar with -prefix-free. Its promise was to let you write DRY code, without all the messy prefixes, that would be standards-compliant in the future (which is why I’m always against adding proprietary features in it, regardless of their popularity). The way -prefix-free works is that it feature tests which CSS features are available only with a prefix, and then adds the prefix in front of their occurences in the code. Nothing will happen if the feature is supported both with and without a prefix or if it’s not supported at all.

This worked well when browsers implementations aren’t significantly different from the unprefixed, standard version. It also works fine when the newer and the older version use incompatible syntaxes. For example, direction keywords in gradients. The old version uses top whereas the new version uses to bottom. If you include both versions, the cascade does its job and ignores the latter version if it’s not supported:

background: linear-gradient(top, white, black);
background: linear-gradient(to bottom, white, black);

However, when the same syntax means different things in the older and the newer version, things can go horribly wrong. Thankfully, this case is quite rare. A prime example of this is linear gradient angles. 0deg means a horizontal (left to right) gradient in prefixed linear-gradients and a vertical (bottom to top) gradient in unprefixed implementations, since they follow the newer Candidate Recommendation rather than the old draft. This wasn’t a problem when every browser supported only prefixed gradients. However, now that IE10 and Firefox 16 are unprefixing their gradients implementations, it was time for me to face the issue I was avoiding ever since I wrote -prefix-free.

The solution I decided on is consistent with -prefix-free’s original promise of allowing you to write mostly standards-compliant code that will not even need -prefix-free in the future. Therefore, it will assume that your gradients use the newer syntax, and if only a prefixed implementation is available, it will convert the angles to the legacy definition. This means that if you update -prefix-free on a page that includes gradients coded with the older definition, they might break. However, they would break anyway in modern browsers, so the sooner the better. Even if you weren’t using -prefix-free at all, and had written all the declarations by hand before the angles changed, you would still have to update your code. Unfortunately, that’s the risk we all take when using experimental features like CSS gradients and I think it’s worth it.

-prefix-free will not take care of any other syntax changes, since when the syntaxes are incompatible, you can easily include both declarations. The angles hotfix was included out of necessity because there is no other way to deal with it.

Here’s a handy JS function that converts older angles to newer ones:

function fromLegacy(deg) { return Math.abs(deg-450) % 360 }

You can read more about the changes in gradient syntax in this excellent IEblog article.

In addition to this change, a new feature was added to -prefix-free. If you ONLY want to use the prefixed version of a feature, but still don’t want to write out of all the prefixes, you can just use -*- as a prefix placeholder and it will be replaced with the current browser’s prefix on runtime. So, if you don’t want to change your angles, you can just prepend -*- to your linear-gradients, like so:

background: -*-linear-gradient(0deg, white, black);

However, it’s a much more futureproof and standards compatible solution to just update your angles to the new definition. You know you’ll have to do it at some point anyway. ;)

Edit: Although -prefix-free doesn’t handle syntax changes in radial gradients, since the syntaxes are mutually incompatible, you may use this little PrefixFree plugin I wrote for the CSS Patterns Gallery, which converts the standard syntax to legacy syntax when needed:

StyleFix.register(function(css, raw) {
	if (PrefixFree.functions.indexOf('radial-gradient') > -1) {
		css = css.replace(/radial-gradient\(([a-z-\s]+\s+)?at ([^,]+)(?=,)/g, function($0, shape, center){
			return 'radial-gradient(' + center + (shape? ', ' + shape : '');

return css; });

Keep in mind however that it’s very crude and not very well tested.

CSS reflections for Firefox, with -moz-element() and SVG masks

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We all know about the proprietary (and imho, horrible) -webkit-box-reflect. However, you can create just as flexible reflections in Firefox as well, by utilizing -moz-element(), some CSS3 and Firefox’s capability to apply SVG effects to HTML elements. And all these are actually standards, so eventually, this will work in all browsers, unlike -webkit-box-reflect, which was never accepted by the CSS WG.

First and foremost, have a look at the demo:

How it works

  • For every element, we generate an ::after pseudoelement with the same dimensions and a position of being right below our original element.
  • Then, we make it appear the same as our element, by giving it a background of ‑moz-element(#element-id) and no content.
  • Reflections are flipped, so we flip it vertically, by applying transform: scaleY(‑1);
  • If we want the reflection to have a little distance from the element (for example 10px like the demo), we also apply a transform of translateY(10px)
  • We want the reflection to not be as opaque as the real element, so we give it an opacity of around 0.3-0.4
  • At this point, we already have a decent reflection, and we didn’t even need SVG masks yet. It’s essentially the same result -webkit-box-reflect gives if you don’t specify a mask image. However, to really make it look like a reflection, we apply a mask through an SVG and the mask CSS property. In this demo, the SVG is external, but it could be a data URI, or even embedded in the HTML.


  • Won’t work with replaced elements (form controls, images etc).
  • If you have borders, it gets a bit more complicated to size it properly
  • Doesn’t degrade gracefully, you still get the pseudoelement in other browsers, so you need to filter it out yourself
  • Bad browser support (currently only Firefox 4+)
  • You need to set the reflection’s background for every element and every element needs an id to use it (but this could be done automatically via script)

Further reading

Credits: Thanks to Christian Heilmann for helping me debug why SVG masks for HTML elements weren’t originally working for me.

My experience from Web Directions @media & Standards.next

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Last week, I was in London to give 2 talks. The first one was last Thursday, in one of the conferences I wanted to go ever since I learned my first CSS properties: Web directions @media. The second one was 2 days later in a smaller event called Standards.next.

Web Directions @media

I managed to get my @media talk early on schedule, so I could relax afterwards and enjoy the rest of the conference. Before I saw the feedback on twitter I thought they hated it, since the audience was silent and didn’t laugh at any of my jokes and asked no questions afterwards. However, I was wrong: The tweets about it were enthusiastic! Here’s a small sample:

You can play with the HTML version of my slides or view them on slideshare:

Mastering CSS3 gradients

View more presentations from Lea Verou

I really enjoyed some of the other talks in @media, especially:


The morning before my Standards.next talk, I woke up with a sore throat, a running nose and a blocked ear. I even thought about cancelling my talk, but I’m one of those people that have to be dying to change their schedule. So I went, and I’m glad I did, as I got to attend Peter Gasston’s incredible talk on CSS3 layout. I really learned so much stuff from that!

As for my talk (“CSS Secrets: 10 things you might not know about CSS3”), it went fine after all. I had some trouble hearing the questions, due to the blocked ear, but nothing too bad. I had trouble with my last demo, as I got confused and used background-origin: padding-box; instead of content-box, but nobody there hated me because of it, like I was afraid would happen if I ever screwed up one of my demos :)

That event was much smaller (it took place in a small room in a pub), so the tweets were much fewer, but still very positive:




I found out afterwards that one particular lady in the audience complained about my pronunciation of the words “fuchsia” and “ems”. That’s what I would’ve said to her if I heard: “Here’s some breaking news to you: Not everyone is a native english speaker. Shocking, isn’t it? I would really be interested to hear your pronunciation if you ever did a presentation in Greek. KKTHXBAI”

Overall, I had a great time in London. I hadn’t been there for more than 10 years, so I had forgotten how beautiful city it is. I loved attending and speaking at both of those events, and I would like to thank Maxine Sherrin and John Allsopp for inviting me to @media and Bruce Lawson for inviting me at Standards.next.

CSS3 patterns gallery and a new pattern

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I finally got around to doing what I wanted to do for quite a few months: Create a gallery with all the basic patterns I was able to create with CSS3 gradients. Here it is:  CSS3 Pattern Gallery

Also, it includes a brand new pattern, which is the hardest one I have ever made so far: Japanese cubes. Thanks to David Storey for challenging me about it.

Supported browsers:

  • Firefox 4 (the patterns themselves work on 3.6 too but the gallery doesn’t due to a JS limitation)
  • Opera 11.10
  • IE10
  • Google Chrome
  • Webkit nightlies

However bear in mind that every implementation has its limitations so a few of them won’t work in all the aforementioned browsers (for example Opera doesn’t support radial gradients and Firefox doesn’t support explicitly sized ones).

Beveled corners & negative border-radius with CSS3 gradients

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Just found out how to do beveled corners and simulate negative border radius without images, by utilizing CSS gradients once again. It’s amazing how many CSS problems can be solved with gradients alone. Read the text in the dabblet below to find out how (or just check the code):

It also falls back to a solid color background if CSS gradients are not supported. It will work on Firefox 3.6+, Chrome, Safari, Opera 11.10+ and IE10+.

PS: For my twitter friends, I had already written this when the robbers came and I was about to post it. I might have been really calm, but not as much as making CSS experiments the same day I was robbed and threatened by a gun :P

Checkerboard pattern with CSS3

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A while ago, I wrote a post on creating simple patterns with CSS3 gradients. A common pattern I was unable to create was that of a regular, non-rotated checkerboard. However, I noticed today that by giving a different background-position to every triangle in the pattern tile, a checkerboard can be easily created:

View in Gecko or Webkit. Webkit seems to have an odd rendering bug, so it needed a background-size override and it still doesn’t look perfect. Oh well, reported the bug and moved on.

Original, Tips, CSS, CSS Images, CSS Values, Multiple Backgrounds, Patterns
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Checkerboard, striped & other background patterns with CSS3 gradients

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Screenshot of the CSS3 patterns I came up withYou’re probably familiar with CSS3 gradients by now, including the closer to the standard Mozilla syntax and the ugly verbose Webkit one. I assume you know how to add multiple color stops, make your gradients angled or create radial gradients. What you might not be aware of, is that CSS3 gradients can be used to create many kinds of commonly needed patterns, including checkered patterns, stripes and more.

View demo (Works in Webkit, Firefox 3.6+, Opera 11.50+ and IE10+)

The main idea behind the technique is the following, taken from the CSS3 Images spec:

If multiple color-stops have the same position, they produce an infinitesimal transition from the one specified first in the rule to the one specified last. In effect, the color suddenly changes at that position rather than smoothly transitioning.

I guess this makes it obvious how to create the tile for the stripes (unless you’ve never created a striped background before, but teaching you this is beyond the scope of this post). For example the gradient for the horizontal stripes is:

background-color: #0ae; background-image: -webkit-gradient(linear, 0 0, 0 100%, color-stop(.5, rgba(255, 255, 255, .2)), color-stop(.5, transparent), to(transparent)); background-image: -moz-linear-gradient(rgba(255, 255, 255, .2) 50%, transparent 50%, transparent); background-image: -o-linear-gradient(rgba(255, 255, 255, .2) 50%, transparent 50%, transparent); background-image: linear-gradient(rgba(255, 255, 255, .2) 50%, transparent 50%, transparent);

Why transparent instead of the actual colors we want? For flexibility. background-color serves two purposes here: Setting the color of half the stripes and serving as a fallback for browsers that don’t support gradients.

However, without anything else, the tile will occupy the whole container. To control the size of each tile, you can use background-size:

-webkit-background-size: 50px 50px; -moz-background-size: 50px 50px; background-size: 50px 50px;

To create the picnic-style pattern, you just overlay horizontal stripes on vertical stripes.

The hardest one to figure out was the checkered pattern. It consists of two 45° linear gradients and two -45° linear gradients, each containing ¼ of the dark squares. I still haven’t managed to think of a way to create a regular checkerboard (not at 45°) without needing an unacceptably large number of gradients. It will be very easily possible if conical gradients start being supported (currently they’re not even in the spec yet).

Can you think of any other popular patterns that can be created with CSS3 and no images? If so, let me know with a comment. Cheers! :)

Added afterwards: Other patterns

There are far more pattern designs possible with CSS3 gradients than I originally thought. For more details, see this later post.

Original, Tips, Background Size, CSS, CSS Images, CSS Values, Multiple Backgrounds, Patterns
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