问题
Usually when I make a gradient I use the colorzilla gradient edtior.
By default it generates the CSS for you. Here is an example:
background: #1e5799; /* Old browsers */
background: -moz-linear-gradient(top, #1e5799 0%, #2989d8 50%, #207cca 51%, #7db9e8 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#1e5799), color-stop(50%,#2989d8), color-stop(51%,#207cca), color-stop(100%,#7db9e8)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* IE10+ */
background: linear-gradient(to bottom, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#1e5799', endColorstr='#7db9e8',GradientType=0 ); /* IE6-9 */
While this is most certainly thorough, I'm curious if it is necessary. Through trial-and-error and process of elimination I have reduced it to the following CSS:
background: #1e5799; /* Old browsers */
background: linear-gradient(to bottom, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#1e5799', endColorstr='#7db9e8',GradientType=0 ); /* IE6-9 */
This reduced CSS still seems to function in Chrome, Firefox, IE8, IE9, and IE10, . However it's tough to say because using the Internet Explorer compatibility view doesn't always work very well (When I had IE9 my block worked, but after I upgraded to IE10 and used IE9 compatibility view it did not). I have also downloaded IETester and have had more success using this tool.
I was just curious if anyone could see if I was missing some vital CSS that might break in a given case or other important browser, or if maybe I could slim this down even more.
While not critical in importance, it makes quite the difference in size.
The difference between the two blocks is 618 bytes and in a sheet that uses 10 gradients, the difference is over 6 KB. As you can see this can add up fast (granted between caching and today's internet speeds it's not the most important factor) and I still think it's worth looking at.
回答1:
Yeah, gradient syntax is a mess. Okay, here goes....
Firstly
filter: IE9 is one you need to watch out for, especially if you're combining gradients with other CSS features.The old IE
filterstyles are based on ActiveX controls and are notoriously buggy, and this tends to be worse when they're combined with other browser features. IE9 introduced standard CSS syntax for most of the stuff thatfilterhad previously been used for; gradients were about the only feature that didn't make it (certainly the only significant one).However those bugs in the ActiveX control for gradients seem to be even more obvious in IE9 than they were in IE8, largely due to the fact that it needs to interract with more built-in browser features than before. For example,
filtergradients do not play nicely withborder-radius. It completely kills the rounded corners. There are a number of other bugs you need to beware of too withfilterstyles.For this reason, many gradient tools will provide you with a whole alternative syntax for IE9, which involves creating an SVG gradient embedded as a data-url into the CSS
background. It's not pretty but it does work better thanfilterfor IE9, as it avoid all thefilterbugs. Unfortunately for this technique, if you also need to support IE8, then thefiltersyntax is still needed; but you don't want it in IE9 to clash with the SVG style, which means CSS hacks or conditional comments or other such nastiness. Yep, it does all get a bit messy.Which is why my honest preferred solution is simply not to support gradients in IE8 or earlier. Too many issues, too much browser-specific code, and an ever-decreasing number of users to make it worth the effort.
When I must support gradients in old IE, I use CSS3Pie, which is a polyfill script that adds support for the standard CSS gradient syntax. This means I can have my gradients in all IE versions without worrying about using a
filterat all. (it uses VML to do the gradient behind the scenes, but you don't need to worry about the implementation details; just the end result).The
-ms-prefix: You're right. This is unnecessary, unless you plan to support the pre-release versions of IE10 (which of course is pointless as anyone using them would have upgraded to the real IE10 by now).The two
-webkit-syntaxes: This is because Webkit introduced the feature before the syntax had been finalised. Such is life on the bleeding edge. Although the syntax is now standardised, we still need to supply the old syntax because there are still a significant number of Safari and other webkit users on versions that use the old syntax. This will change over time, but it's not ready to be dropped yet.The
-o-prefix: This is for the Opera browser. It is only in the latest release that they dropped the need for the prefix. Any users not on the latest release will need it. It's your call as to how many users this might affect and therefore whether you can drop it or not. I'd say it's probably okay, as Opera users tend to keep their browser up-to-date.The
-moz-prefix: You can safely drop this now. Firefox hasn't needed the prefix since v16. There are very very few users on version earlier than that now. (even the Long Term Support version is FF17).The plain-colour fallback: Keep this of course. Make sure your site looks okay with it (it doesn't have to look amazing; just okay). This is your insurance policy for users on old browsers. And yes, that may include people who have eg an old Firefox version that requires a prefix that you're not supporting.
So yes, the short answer is that you can drop a lot of it; not quite as much as you wanted to, but certainly some of it.
I'd write your code as follows:
background: #1e5799; /* Old browsers */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#1e5799), color-stop(50%,#2989d8), color-stop(51%,#207cca), color-stop(100%,#7db9e8)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* Chrome10+,Safari5.1+ */
-pie-background: linear-gradient(to bottom, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* IE6-9 with css3Pie */
background: linear-gradient(to bottom, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* W3C */
behavior: url(/PIE.htc); /* activate css3Pie in IE6-9 */
I've removed the -o- and -moz- prefixes and replaced the filter with CSS3Pie code (you'd obviously need to add PIE.htc to your site, but only IE will download it).
Hope that helps.
I also suggest looking at the CanIUse site for a full browser support chart.
回答2:
You still (as of today) need the -webkit- prefix for Safari, on Mac OS X and iOS.
- http://caniuse.com/#search=gradients
You also need the -moz-- and -webkit--prefixed versions for older versions of Firefox and Chrome.
“Aha,” you say, “but those browsers auto-update now!”
“Why yes,” I reply, wearing a patient smile, “but not on old Android phones they don’t.”
-ms-linear-gradient wasn’t ever supported though (IE 9 didn’t support CSS gradients, just filter and SVG backgrounds, and IE 10 supports linear-gradient), so you can drop that. (And if you can find anyone still using Opera, you can ask them how they feel about gradients.)
However, as I commented: once your CSS is gzipped, the additional gradient declarations don’t take up much extra space. Obviously it’s up to you to balance the size difference against the browsers you want to support, but I’d suggest you judge based on size after gzipping, and (if possible) based on the browsers your audience (and intended audience) are actually using.
来源：https://stackoverflow.com/questions/17201785/minimum-css-required-for-gradients-ie8