How can I make a spray with a transperant background?

Hey guys, I’m trying to create a few sprays for a game but I need their backgrounds to be transperant. How would I do this? I’ve used bmps, jpgs, pngs, psds and tgas and i can’t get it working? Can you help me out?

TGA 32 bit

That isn’t the most helpful reply still explains alot though.
You need to add a alpha/transparency mask then remove the background or what ever else and it should become grey checkboard where it’s transparent.

Tab next to Layers = Channels
Make a new channel (it will be alpha by default.)

Merge your spray image and hit Ctrl on the layer image. It should select opaque parts of the spray.

Select your alpha channel and hit Shift + F5. Set to 100% and apply.

Save image as .tga 32bit compressed or .vtf with alpha (assuming you know how to make a vtf)

Protip: You can’t do it in MSPaint.

Go to getpaint.net and download that. It’s much better (and what Ghostwork used in his example if I see correctly).

I’m not sure if I used 32-bit but I’ll be sure to try some other suggestions. Thanks guys.