iamvdoPostCSS Opacity 
PostCSS plugin that adds support for legacy browser opacity alternatives.
Example
postcss([
require('postcss-opacity')
])
/* Input example */
.foo {
opacity: .5;
}
/* Output example */
.foo {
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
opacity: .5;
}
Legacy
Support for IE 5-7, Safari 1.X, Netscape
postcss([
require('postcss-opacity')({
legacy: true
})
])
/* Input example */
.foo {
opacity: .5;
}
/* Output example */
.foo {
/* IE 8 */
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
/* IE 5-7 */
filter: alpha(opacity=50);
/* Netscape */
-moz-opacity: .5;
/* Safari 1.x */
-khtml-opacity: .5;
/* Modern browsers */
opacity: .5;
}
See PostCSS docs for examples for your environment.