Editing alpha channel to your image. Alpha channel is the transparent part of your image which for example OFP and ArmA uses for transparency like in vegetation or vehicle window textures.

Editing alpha channel in PaintShop Pro by Gnat

1 - open the image in a PaintShop Pro
2 - save as uncompressed 24bit TGA file
3 - use magic wand to select the background only as mask
4 - invert the mask
5 - select “save mask to alpha”
6 - save TGA again
7 - done

EDIT: Note: TGA file must be save as 24bit (with alpha channel) and UNCOMPRESSED

Editing alpha channel in Photoshop

You make logo normally when you finish painting select all places what you want to be transparency an from menu selections choose invert and from the same menu choose save to alpha channel save and it is all. Now save file as 24 bit uncompressed tga.

Paint all that you want transparent a color like gray or that differs from your texture completely. That way its real easy to select the area that you want transparent using the “Magic Wand” And continue on with the method stated above.

STGN posted this:
If you are making a complex shape or has fading/different amounts of transparency in the same texture like a iron sight reticule make a black background and make a copy of you reticule, if you are using multiple layers merge the copies and under “layer styles” use color overlay and change it to white.

Now you should have a black and white picture. Mark all of the texture and “copy merge”, now go to the Alpha layer and “copy paste” you should now have a transparency texture as detailed as the original texture.

Sometimes its also a good idea to just leave complete main texture in a single color and just have the Alpha layer make the details. Like a BIS reticule its often just black when you not viewing the the alpha layer which has all the detail.