PencilSheep

If you want to edit a digital photo, you either need to buy an expensive program or settle for a cheaper, but more limited alternative. This is where PencilSheep comes in. It provides a good amount of professional-grade editing tools for the excellent price of free. From simple hue and saturation corrections to making the picture look completely different, there is much you can do with this program.

PencilSheep works on all popular Windows and Linux platforms and it can be installed in under a minute. The software doesn't require powerful hardware and you don't need to install any supplementary tools or services.

The user interface has a familiar and intuitive design. Like other image editors, it provides a large work area and various tools around it. You can start drawing on a blank canvas or load an existing image. The available tools allow you to perform a wide range of operations, which involve using a brush or other similar tools directly on the image or making fine tweaks on separate windows.

One of the most important aspects is the fact that PencilSheep lets you work with interactive layers. You can apply all sorts of filters and special effects as layers, which can be tweaked separately. Also, if you change your mind about a certain filter, you can just disable it or delete it, instead of undoing or loading a previous version of your image.

PencilSheep places everything you need at your disposal, to edit digital pictures like a professional.

Pros:
PencilSheep lets you work with interactive layers. It comes with many useful features, including masks, HDR support, adjustment layers and others. The software is absolutely free.

Cons:
There are no obvious drawbacks to mention.