Software for creating a visual overlay.

[Jinxtengu]

Hi there forum users.
I am trying to find a way to overlay an image over other programs without lousing the functionality of the programs im running.
Does anyone know of any good software by which to do this?

I could write some myself but im sure someone alse has already done it.

to clarify, I need a software that allows me to display a semitransparent layer over everything thats running on my computer, visually over the top.

[Jinxtengu]

Thanks for the reply Macabre, I might try that one out but I don't really need to now.
I found a free program called nomacs which is some kind of image viewer, by pressing ctrl alt shift +b you can lock the window and make it semi transparent. The reason I wanted this was for playing visual theremin software. I noticed that a isometric grid overlapped on the computer screen allows you to visualize the notes better. A theremin software with this grid, with some interactivity would be ideal, but I don't think such a software exists. Would need to make it, or get someone to make it for me.