Though Photoshop is the great image/graphics tool but it is expensive to buy. But there are some applications which can function nearly as Photoshop and are freely available to download without any registration or activation. Some of these are GiMP, PhotoFilter, PaintShop Pro etc.
It has many capabilities. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.
GIMP is expandable and extensible. It is designed to be augmented with plug-ins and extensions to do just about anything. The advanced scripting interface allows everything from the simplest task to the most complex image manipulation procedures to be easily scripted"
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As per oldversion.com : "Paint Shop Pro (PSP) is a bitmap graphics editor and vector graphics editor for computers running the Microsoft Windows operating system that was originally published by Minneapolis-based Jasc Software. In October 2004, Corel Corporation purchased Jasc Software, and with it, the distribution rights to Paint Shop Pro."