I need a black box filled with transparent text above the background image.
See this example:
Is it possible? If so, how can I do this?
While there is no cross-browser solution, only webkit seems to support masks.
-webkit-mask-image: url(/path/to/mask.png);
http://trentwalton.com/2011/05/19/mask-image-text/
Here is a great reference showing what you just want what you need.
http://www.silenceit.ca/2011/03/11/css-gradients-and-webkit-image-masks-on-text/
However, the solution, as with all alpha masks, is not fully compatible with the browser. I'm afraid!