Paint.NET is a free image and photo editing software. It features an intuitive and innovative user interface with support for layers, unlimited undo special effects, and various valuable and powerful tools (Source: Paint.NET Homepage). The software was initially created as a replacement for MS Paint, which provides only a minimum of features, even though it has existed for quite some time. If you ever wanted to do some real editing on some images, then you know that MS Paint is pretty much useless.
Features
Paint.NET is not just software with lots of features. It can be extended with plug-ins to do things usually only available in paid software. For example, you can work on multiple layers, use professional graphic tools, or apply effects to images. And to get even closer to big players like Photoshop, you can use the Paint.NET PSD Plug-in, which allows you to open and edit Photoshop (.PSD) files with multiple layers. This is especially important because the .PSD format is a de facto standard in the graphics industry. And many cool Photoshop effects can also be implemented into Paint.NET via plug-ins.
But keep in mind that Photoshop itself can be extended through plug-ins. That means that there are many features you will not find in Paint.NET. However, this free application provides much more than a simple picture editor. And if you, like me, are not a professional graphics designer, then Paint.NET is really all you need.
Alternatives
If you need even more features, you might want to try the Open Source Tool GIMP. Its pool of features is almost as massive as that of Photoshop, but it is also more challenging to use. As a matter of fact, GIMP and Photoshop are both very complex applications, and the main difference is that GIMP is available for free, whereas Photoshop is quite expensive.
On the other hand, if you just need a picture viewer with some editing features (e.g., red-eye removal), we recommend XnView. This little application opens pretty much every graphics format you can imagine. It is the best picture viewer we have found so far.
