GIMP 2.8.10

Create and edit graphics and digital photos with this world class open source graphic editing tool.

In today's graphic intensive world, having a decent, full featured editor is a must.  Many top of the line packages come with the features everyone wants, and unfortunately, with the price tag to go with it.  This is one of the reasons why I like GIMP. It’s a full featured, multi-platform graphics editor; and its totally awesome.

GIMP is the image editing tool of choice for many users, in large part due to its many editing tools.  It's more common tools include a paint brush, pencil, airbrush, eraser and ink tools. You can use them to create new or blended pixels. Tools such as the bucket fill and blend tools are used to change large regions of space in an image and can be used to help blend images. 

GIMP also has a selection of smart tools.  These use a more complex algorithm to enable a user to complete time consuming or difficult tasks, and include the clone tool that copies pixels using a brush, and the healing brush which copies pixels from an area and corrects the tone and color where it is being used. The perspective clone tool works in a similar way to the clone tool, but also allows a user to alter and correct distance changes. The blur and sharpen tool is a brush that blurs and sharpens sections of an image; and the dodge and burn tool is a brush that makes target pixels lighter (dodges) or darker (burns).

An image being edited in GIMP can consist of many layers. Each layer in an image is made up of several channels. In an RGB image there are normally 3 or 4 channels, consisting of a red, green and blue channel. Color sub-layers look like slightly different gray images, but when put together they make a complete image. The fourth channel that may be part of a layer is the alpha channel (or layer mask), this channel measures opacity where a whole or part of an image can be completely visible, partially visible or invisible.

GIMP has several ways of selecting colors including palettes, color choosers and using an eyedropper tool to select a color on the canvas. The built-in color choosers include RGB/HSV selector or scales, water-color selector, CMYK selector and a color-wheel selector. Colors in GIMP can also be selected using hexadecimal color codes as used in HTML color selection; and it has native support for indexed color and RGB color spaces. Other color spaces are supported using decomposition where each channel of the new color space becomes a black and white image. CMYK, LAB and HSV (hue, saturation, value) are supported this way. GIMP does color blending through its blend tool. You apply a gradient to the surface of an image using GIMP's color modes. Gradients can also be integrated into tools such as the brush tool.  When the user paints this way, the output color slowly changes. 

Pros: Free, advanced image editing.

Cons: Advanced features require knowledge of graphic arts and advanced editing techniques to take full advantage of.

Conclusion: GIMP is an advanced image editing tool on par with Photoshop and other expensive, best of class graphic editing tools. The best thing about it is that its powerful and its free.  You're going to need to understand multi-layered imaging, masks and color channels to take full advantage of the tool.