If Photoshop’s $700 price scares you, and a bootleg copy is not your cup of tea, there is GIMP – a powerful image editing tool from the open source community which is absolutely free. It runs on Windows too, also Mac OS X and, of course, Linux. And it’s very good.
To learn how to use GIMP, there is a book that you can use, written by architect and photographer Klaus Goelker of Germany. GIMP 2.6 for Photographers, (Rocky Nook, $39.95 USD) is a beginner’s guide to the only open source image-editing tool that provides a no-cost alternative to expensive programs such as Photoshop.
Topics include the basics of image editing and simple adjustments, as well as advanced techniques using layers and masks, stitching panoramic images, and preparing high-quality black and white images. The most important editing functions are presented in individual, easy-to-follow workshops.
GIMP 2.6 for Photographers has evolved from classroom materials that the author developed and taught in courses and workshops on image editing with the GIMP.
[Site: O’Reilly]