You can use rgba()
in css to define a color instead of rgb()
. Like this:
style='background-color: rgba(128,128,128, 0.7);
Gives you the same color as rgb(128,128,128)
but with a 70% opacity so the stuff behind only shows thru 30%. CSS3 but it's worked in most browsers since 2008. Sorry, no #rrggbb syntax that I know of. Play with the numbers - you can wash out with white, shadow out with gray, whatever you want to dilute with.
OK so you make a a rectangle in semi-transparent gray (or whatever color) and lay it on top of your image, maybe with position:absolute and a z-index higher than zero, and you put it just before your image and the default location for the rectangle will be the same upper-left corner of your image. Should work.