Adobe Photoshop is a great product. I have been using it since 2003 and I simply love its functionality and ease of use. If there is anything to complaint about, then it has to be the high cost (US$649) involved in buying the software.
For those who can’t afford Photoshop, here is a list of the 5 great free alternative to Photoshop.
There is no doubt that GIMP is the closest alternative to Photoshop. GIMP is used by many professionals and contains most of the functions in Photoshop. While some people dislike the interface and find it hard to use, there are still many others who love this open source software. You can find a huge user community supporting this product. Many Linux distributions have also used GIMP as the default image editing program. GIMP is available for Linux, Windows and Mac OSX.
Using GIMP as the backend, GIMPshop added an extra interface to make it looks and functions more like Photoshop. If you are looking for Photoshop alternative, but hate the interface of GIMP, you might want to try out GIMPshop
Krita is a painting and image editing application for Koffice and is part of the KDE package. It has become very popular recently due to its ease of use. While it is not as feature-rich as the Photoshop, or even GIMP, it does contains the necessary tools to create/edit a professional image from scratch. In fact, the latest version contains some features that are not found in both GIMP and Photoshop.
Paint.NET is more than the default Paint application in Windows. Originally designed as a free replacement for the Microsoft Paint, it has grown substantially to become a simple, yet powerful image editor. While still not on par with Photoshop, it does have plenty of useful features such as layers and filters. Currently, Paint.net can only be used on computers that run Windows, however a project that ports Paint.net to Linux, via mono is available for Hardy Heron. It is still not stable, but if you are adventurous enough, you might want to try it in your Hardy. To install Paint.net, add the following repository to your /etc/apt/sources.list
deb http://ppa.launchpad.net/xmlich02/ubuntu hardy main sudo apt-get install paint-mono
CinePaint is a deep paint image retouching tool that supports higher color fidelity than ordinary painting tools. One of the advantage that it has over GIMP is that it is able to support 32-bits image (GIMP only supports 8-bits image). Cinepaint is mainly used by developers in the flim industry for motion picture frame-by-frame retouching. The current version runs on Linux, BSD, Mac OSX. Stable version for Windows is not available at the moment.