Implement RGBA() colors for modern web browsers

!!! See update version »»» (CANVAS Free version)

I tried to implement rgba to see if I can get it work, unfortunately I had encountered these issues:

Internet Explore 6+ won't render rgba() and doesn't accept rgba()as valid backgound-color
Firefox 2.0- and Opera 9.21- does not understand rgba(), too
Safari 2.0+ seems to work well with rgba()

Apparently, I need to do some hacks for Firefox 2, Opera 9 and IE6+.

For Internet Explorer, I found that I can use Alpha Component which seems to a very little known by many developers.

"In many cases, color is expanded to include the Alpha component (#AARRGGBB) in the Internet Explorer 5.5 filters."

Alpha Component seems to be great for Internet Explorer to render any hex colors with any opacity.

Also, it came to my mind that I can use gradient filter for any block elements with hasLayout and all I need to do is to set both the start and end colors for gradient to be the same color.

Here's what the sample CSS codes for IE may look like:

Now we're done with IE, then we can hack Firefox and Opera

Since both Firefox and Opera do support CANVAS, I planed to use an abstract CANVAS component to generate a Base 64 encoded translucent image then apply this image to the background.

In order to do this, I use a method toDataUrl() supported by both Fire and Opera to get the uri of background-image

Here's what the sample CSS codes for Firefox and Opera may look like:

.element{ /*color = black, opacity = 0.6 */ background:transparent url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAGElEQVQYlWPkYOZ6xkAEYCJG0ahC6ikEAJ/nAQ92k8jOAAAAAElFTkSuQmCC); }

Note that Firefox 3 will start to support rgba() or maybe newer versions of Opera will do, too. So I do check the DOM support for rgab() before I start to hack a browser

var p_useRGBA = false; try { p_useRGBA = document.createElement('var'); //Firefox2-, Opera 9.02- will return empty string //IE will throw an Error for invalid assignment of background-color p_useRGBA.style.backgroundColor = 'rgba(255,255,255,1)' ; p_useRGBA = !!p_useRGBA.style.backgroundColor; }catch(err){ p_useRGBA = false ;}; alert( p_useRGBA );

Finally, I've got my little JavaScript library done, which is compatible and tested with IE6, IE7, Safari 2.0+, Firefox 2.0, Opera 9.21+

Just feel free to use or extend it or you can simply grab my static HTML example.

Cheers!

Hedger Wang

Examples

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