Well, I have a cheap, out dated version of photoshop that doesn't export alpha channel. I tried using free tools, but I couldn't directly edit the alpha channel the way I wanted to. So I wrote my own.

My C++ program can extract the alpha channel from an image, so you can edit it, and then you can insert back into the original image.

The Alpha tool extracts the alpha channel from a 32-bit bitmap, and saves the 'A' from rgba on the r, g, and b of another 32-bit bitmap. Then you have to convert the 32-bit bitmap 24-bit bitmap using microsoft's imagetool.exe (get it here http://www.scenery.org/tutorials_fs2k4_SDK.htm it's in the fs2004_sdk_bglcomp2_setup.exe (857KB)).
Edit the 24-bit one which represents the alpha channel, and then insert it back into the original image.

I just finished it a couple of minutes ago. Anyone that would like this tool?
Here's an example of an extracted alpha channel:

You could edit it, and then slip it back into the original file. This a great help to me for editing BF textures.

Good job on that tool, it's pretty neat.

However, GIMP can do that for you. With Image -> Mode you can compose or decompose any texture (into R, G, B, alpha). I use it often to put alpha textures into objects or just to edit the alpha texture. When you deselect "decompose to layers," you get 3 (or 4, if there's an alpha) distinct textures, which you can then re-compose (with an entirely new alpha layer or an edited one) back into a single .tga.

However, if you like your tool better, then whatever works best for you. That was just in case you were unaware.

Thank you for the gimp help! I tried to download GIMP, but at the time the download link was broken. Now that I found the download link works, after I wrote that tool. *sigh*
There is no difference between GIMP and mine, so I think I going to use it, can't let all that work go to waste. It's an amazing feeling to write something from scratch that works. No doubt GIMP will prove to be a valuable tool in the future, though. Maybe I should expand my tool? But why bother if GIMP is so good.