This is often thought of as “top of the pile” when it come to free Image Editing Software. The reality is it can do far more than many of the paid graphics programs you will come across. If you can’t produce professional standard work with GIMP the the fault definitely lies with you rather than the program. There are versions available for Windows XP and onwards plus Linux.
There are a couple of issues with the program which may put you off. It isn’t aimed at the beginner, it is probably best that you have a reasonable amount of graphics experience before you try and use it, unless you really want to spend a lot of time with the manual. Also it doesn’t have the same live rendering capabilities that a program such as paint.net has. So one you chose the colours for a gradient and implement it you will need to “undo” it and do it again if you don’t like it. (with paint.net you can change the colour on this type of tool “on the fly”).
Having said that the add-ons and effects available with GIMP are astounding. It can do things with 3D mapping which I have only ever found in this program. Although I do use Paint.net as my “go to” graphic creator I keep a copy of GIMP on my computer for when I need that extra special effect.
One of the first things you will notice about GIMP when you launch it is it default mode is multi window. Personally I find this very confusing mainly due to it being different from any other program I use. Luckily there is now a “Single Window Mode” which you will find under the “Windows” menu.
If you are serious about your Image Editing software then I strongly recommend GIMP 2 although it is a bit of overkill if you just want to tweak a few photographs.
You can download this Image Editing Software for free from http://www.gimp.org/
Available for Windows and Linux.
As normal you should only download this program via it’s official site. Copies obtained elsewhere may contain malware etc.