GIMP

For years now, GIMP has been one of the best free alternatives for commercial image editing suites like Photoshop or Corel Draw. GNU, (Image Manipulation Program) is a multi-platform open-source tool that lets you perform practically the same actions as paid software.

You can use GIMP both to retouch images and to create new ones. The app's tools include a brush, pencil, clone pad, and airbrush. GIMP's features are virtually the same as those of any current image editor: layer system, alpha channels, operation history, selection and transformation tools, masks, gradients, and so on. You can also use GIMP to convert images between formats, batch process files, compose vector images, or edit motion graphics formats. Plus, the program's functionality can be extended through the use of plug-ins. There are more than a hundred of them.

GIMP can work with virtually all current image formats, such as BMP, GIF, JPEG, MNG, PCX, PNG, PSD, PS, PDF, TIFF, TGA, SVG or XPM. In addition, its fragmented interface can be particularly useful because you can always modify the layout of the floating windows to suit your preferences or revert to the classic system to make it more like Adobe tools.