Is there a way to add transparency to a background-image using CSS3?
There is a perfect tool named: Petteriny (transparent pixel maker) which create any transparency pattern you need . It also generate the CSS you need. here is an example what this tool makes.
.myDiv{background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAYAAABytg0kAAAAFklEQVQIW2NUTmk3vjun8iwjAxCAOAA2KgVERG1HmQAAAABJRU5ErkJggg==
) repeat;}
You use it, this like this in your html
your text over image
In this tool it's also possible to download the pattern