Copyright © 2010 Christian “Schepp” Schaefer
http://twitter.com/derSchepp

About “Chroma Corners”

“Chroma Corners” is the name of a new technique to create rounded corners in IE 6 – 8. It uses IE’s chroma-filter as a tool to mask away corner areas, which are created as a graphic and which are filled with a solid color.
It is and behaves like standard HTML + CSS as opposed to the newer VML-based approches. It gives you more freeness and needs less photoshopping work than older background image based techniques for rounded corners like “Mountain Top” or “Sliding Doors”.

Usage

You can use this solution for all borderless rounded elements and for bordered elements with a solid border-style in one single border-color.

This is how you use “Chroma Corners”:

.borderradius {
  -moz-border-radius: 14px;
  -webkit-border-radius: 14px;
  border-radius: 14px;
  behavior: url(chromacorners.htc); /* relative path from HTML-file! */
}

or:

.borderradius {
  -moz-border-radius: 14px 4px;
  -webkit-border-radius: 14px 4px;
  border-radius: 14px 4px;
  behavior: url(chromacorners.htc); /* relative path from HTML-file! */
}

or:

.borderradius {
  -moz-border-radius: 14px 4px 14px 4px;
  -webkit-border-radius: 14px 4px 14px 4px;
  border-radius: 14px 4px 14px 4px;
  behavior: url(chromacorners.htc); /* relative path from HTML-file! */
}

or:

.borderradius {
  -moz-border-top-left-radius: 14px;
  -webkit-border-top-left-radius: 14px;
  border-top-left-radius: 14px;
  behavior: url(chromacorners.htc); /* relative path from HTML-file! */
}

or:

.borderradius {
  -moz-border-radius: 14px;
  -webkit-border-radius: 14px;
  border-radius: 14px;
  border: black 1px solid;
  behavior: url(chromacorners.htc); /* relative path from HTML-file! */
}

Important: Please note that you need to set the url of the behavior not relative to the stylesheet but relative to the HTML-document. The best thing is to use an absolute path e.g.: behavior: url(/css/chromacorners/chromacorners.htc);.

Caveats

In order for this technique to work, the behavior will apply position: relative; to the to be rounded element. Keep that in mind when absolutely positioning children of the rounded one.

System Requirements

Your webspace must be running PHP 5 (no PHP 4, we are in 2010!) and GDLib v2 extension must enabled.

3rd party elements used

This behavior comes together with a PHP-script named “Rounded PHP” origined from here:
http://sourceforge.net/projects/roundedphp/
You will find all the license and author infomation inside the folder rounded-php.

In addition it borrowed a function from Dean Edward’s IE7 framework found here:
http://code.google.com/p/ie7-js/
MIT License (http://www.opensource.org/licenses/mit-license.php)