TGA Tool

TGA Tool is a very simple application that enables you to open and edit 32-bit TGA images, providing a few useful utilities to help you in this regard.
The program is quite basic and in case you like it and decide to use it on a regular basis with all of your TGA files, there's no settings menu to set file associations (as such, you have to perform this from Windows).
On the other hand, TGA Tool is not only able to open TGA files, but it's also compatible with PNG, BMP and JPG formats, so it can very well become a basic replacement for the built-in Windows Image Viewer.
TGA Tool provides dedicated tools to edit the Alpha Channel, so you can adjust pixel brightness, load from file and work with mask colors or uniform levels.
While all of these features perform just as they are supposed to, there's no real time preview, which means you can only view the modifications after applying them.
Last but not least, TGA Tool allows you to configure saturation, but again, there’s no preview window, which makes things a bit difficult especially when editing pictures on a regular basis. The application can save the edited photos with the TGA extension, so it can also serve as an image converter.
Of course, it's more or less obvious that TGA Tool runs on low computer resources on all Windows versions, both old and new, without errors or compatibility issues at all.
Which leads us to a pretty simple conclusion: TGA Tool is the easiest way to deal with the TGA format and as long as you need some basic editing features, this is the app to get.