Top 5 Best Alternatives to Adobe Photoshop1. GIMP
GIMP/GNU Image Manipulation Program is a freely distributed piece of software that is suitable for such tasks as photo-retouching, image-composition, image-authoring. GIMP is a powerful software with capabilities not found in any other free software product. It can used as a simple paint program, an expert-quality photo retouching program, an online batch processing system, a mass production image render, or an image format converter. It is modular, expandable, and extensible. It is designed to be augmented with plugins and extensions to do just about anything. GIMP is the best alternative to Photoshop. GIMP is compatible with Windows, OS X and Linux machines and comes completely Open-source.
2. Adobe Photoshop Lightroom
Adobe Photoshop Lightroom is a powerful & versatile program for editing and enhancing your photos, as well as compiling them into a slideshow. Perfect your shots with advanced controls for tone, contrast, color, and more. Keywords and collections make it easy to categorize, find, and manage your favorite photos; it efficiently organize all your photos & share them almost anywhere. Lightroom Develop module to make non destructive adjustments, such as cropping, color-correction, spot-removal, tonal-adjustments, and exposure. It has an intuitive interface and plenty of builtin tips along the way, this program makes advanced editing features available to all experience levels. You can experiment without limits in a nondestructive editing environment.
Paint.NET is a full featured image editing program that gives you tons of tools to work; through an intuitive and streamlined interface. It features an innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. Paint.Net may not be a huge inconvenience, but it does add an extra step to a lot of projects. Paint.NET provides nearly as much functionality as some of the more highly rated image editing programs and makes these features available to everyone. Also an active and growing online community provides friendly help, tutorials, and plugins.
4. Pixel Mator
Pixel Mator for Mac is a powerful, fast, easy to use image editor. It lets you enhance and touch up photos, sketch, draw and paint, add text and shapes, apply dazzling effects. Pixelmator brings an incredibly smart Quick Selection tool, a precise yet easy to use Magnetic Selection tool, a full set of powerful Pixel mator retouching tools to the Photos app. It's smart & powerful Move Tool lets you easily move, rotate, and distort any element, selection, text, shape, or an entire layer. And you can Paint as realistically as on canvas, etc.
5. Pixlr Editor
Pixlr Editor is the creator of online cloud based image tools & utilities. It has three applications: Pixlr Editor, Pixlr Express and Pixlr-o-matic. It built in Flash and all you need to have the Flash plugin to get it to work. It also provide screen grabbing tools Pixlr Grabber and one click photo sharing imm.io. Pixlr Editor on the other hand is a richly featured web app that offers a healthy dose of features for editing photos and images.
So which one is your favorite; don't forget to mention :)