There are hundreds of image-processing programs for Windows, including many that are free. But users of Apple's Mac OS X have comparatively few image editors to choose from. OS X is still new, and the downturn in technology stocks has hurt the development of all new software, not just OS X programs. Here are some free image editors for Mac users.

1.iPhoto, the image manager that Apple supplies free for all Mac users, has a borderline image editor, providing only the basics -- cropping, scaling, rotating, brightness, red-eye fixing, importing, exporting and, of course, photo management in general. (That's iPhoto's big strength.) Apple improved iPhoto a few months ago, adding much-needed functions, so if you already have iPhoto but don't have the latest version, go get it. But even with the new functions, iPhoto is handy, helpful, superbly designed for basic operations and, unfortunately, too limited for serious work.

2.PixelNhance is a real-time image enhancement application that lets you quickly and easily determine the best image adjustment settings for your image. For example, you can open up a document in PixelNhance and find the optimal sharpness for that image in a matter of seconds. Your image appears in a unique split-screen window with the original settings on one side and the settings that you currently have in the Controls window on the other. You can horizontally, vertically, or diagonally move, as well as rotate, the dividing bar that separates the two regions.

3.Image Tricks is a free image editor for Mac OS X 10.4 aka Tiger. Image Tricks is based on Apple Core Image filters and includes about 35 Image Units (blur, distortion, stylize filters, tile effects and more).
Image Tricks includes the following Image Units and key features:
Distortion filters (twirl, bump, pinch and more)
Stylish filters (mosaic, crystalize, use halftone effects, etc.)
Blur filters (zoom, motion, etc.)
Color adjustment filters (saturation, brightness, contrast, hue, etc.)
Tile, kaleidoscope and crop images
Effects filters (crystallize, bloom, gloom, etc.)
iPhoto integration
Import all kinds of images (over 20 formats including TIFF, JPEG, GIF, PDF, EPS)
Export to TIFF and JPEG formats.

4. Seashore is an open source image editor for Mac OS X's Cocoa framework. It features gradients, textures and anti-aliasing for both text and brush strokes. It supports multiple layers and alpha channel editing. It is based around the GIMP's technology and uses the same native file format.

However, unlike the GIMP, Seashore only aims to serve the basic image editing needs of most computer users, not to provide a replacement for professional image editing products. Seashore was created by Mark Pazolli who, together with a handful of other developers and helpful users, still develops it to this day.

5. ChocoFlopis a free photo and image editor for OS X, that reads and writes all the popular file formats. The license is free until the application is no longer in development. The download page includes more free filters and third party plugins.
NOTE: The serial number might change from time to time. You can read the post on the application developers site by clicking here to get the latest serial number.

6.CinePaint is an open source painting program used by motion picture studios to retouch images in 35mm films. It was formerly called Film Gimp. It has been used in a dozen feature films including Harry Potter, Scooby-Doo, and the Fast & the Furious.

7.GIMP is the GNU Image Manipulation Program. It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. It works on many operating systems, in many languages.

8.Gimpshop If you've never used Photoshop before, you may not appreciate my GIMPshop hack. What I've done is renamed and reorganized GIMP's tools, options, windows, and menus to closely resemble Adobe Photoshop's menu structure and naming conventions. Many of the menu options and even whole menus were recreated to faithfully reproduce a Photoshop-like experience. After running my GIMPshop hack, you'll find that Photoshop and the GIMP are strikingly similar.

9.Goldberg Goldberg is a freeware image and movie viewer with image editing capabilities and support for applying QuickTime and other effects. Version 2.0 is a major rewrite and offers rotation capabilities, free zooming, undo support and more.

10. ImageMagickis a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a large variety of formats. Images can be cropped, colors can be changed, various effects can be applied, images can be rotated and combined, and text, lines, polygons, ellipses and Bezier curves can be added to images and stretc.hed and rotated.
Most of the functionality of ImageMagick can be used interactively from the command line; more often, however, the features are used from programs written in the programming languages C, Ch, C++, Java, Lisp, Pascal, Perl, PHP, Python, Ruby, Tcl/Tk, for which ready-made ImageMagick interfaces (MagickCore, MagickWand, PerlMagick, Magick++, PythonMagick, MagickWand for PHP, RMagick, TclMagick, L_Magick, and JMagick) are available. This makes it possible to modify or create images automatically and dynamically.
ImageMagick supports many image formats (over 95) including formats like GIF, JPEG, JPEG-2000, PNG, PDF, PhotoCD, TIFF, and DPX.

11.Pixen is an innovative graphics editor for the Mac. It's designed from top to bottom for pixel artists - people who make low-resolution raster art like the sprites you see in old video games. But it's great for artists of all arenas: Pixen is like a very powerful MSPaint or a simpler, more agile Photoshop. And best of all, it's Free!