Introduction to the “GIMP” for Educators

(some terms are defined at the bottom of this article)

The “Gimp” stands for GNU Image Manipulation Program. The Gimp is a free image editing program that has quite a bit of power. Chiefly it works with “raster” images (also known as bitmaps) and can handle many popular file formats including JPEG, GIF, and PNG. Its great for editing digital photographs and can be used as a drawing tool if you like to use raster editors to create images. The Gimp was not created specifically to be a competitor or replacement to Adobe Photoshop though it is often compared with Photoshop and in my personal opinion can easily handle 100% of the needs of a casual digital image editor, educator, or student.

The Gimp is available for multiple platforms (Windows, UNIX, OS X, and others) and is licensed under the GNU public license including totally open source code. It is one of the most popular and well known pieces of open source software. It is supported by a large community of users and a responsive community of developers that maintain, improve, and add to the program on a regular basis. There are also forums and on line documentation to help users learn how to use the Gimp’s many tools and features. One criticism of the Gimp has been that its user interface has been a bit clunky and hard to learn or use. I agree that there is room for improvement but having used the Gimp from its early days through its current incarnation I do think that they have improved the UI quite a bit over time and I have read about plans to further improve it as time goes on. There is even a fork in the Gimp code base that arranges the user interface, buttons, and control-key sequences to be much more like photoshop for those who are expert users of that software.

Some of the common tasks that I use the Gimp for include cropping photographs, changing the size/resolution of a photograph, taking the backgrounds out of images, compositing two or more images together, and adding text annotations to images. It supports concepts similar to photoshop including layers, channels, paths, brushes and plugins. It also has some useful tools for web developers including a button generator, logo generator, and image map generator.

Educators can make use of the Gimp in three main areas:

1) A free and relatively easy to use tool to edit images that you may use when building presentations, handouts, worksheets, tests, web content, or any other digital or print media. Since it runs on all platforms and is free, you can use it at home as well as at school. So even if your school has Apple and you have a PC at home (or vice versa) you can still get work done on your own terms.

2) A free tool that will work on any platform including older machines that you can use to teach students concepts of digital photography, image editing, or as a tool for students to edit images used in their own reports and presentations. As we move more and more into the age of WEB 2.0 students are going to be asked to create presentations, web pages, social media and report and publish their projects for others to see and use. A tool like the Gimp gives them a tool that will let them get this job done AND can teach them concepts they may one day need in their careers as they are called upon to create reports, publish content to a web page, or do more complex tasks.

3) A tool for scientific analysis of digital images taken for scientific purposes. It is possible to strip out certain color bands, adjust brightness and contrast, take measurements, and form conclusions based upon image data. Color analysis of pH indicators or from some other chemical reaction comes to mind. Spectral analysis may be another possibility.

Here are some resources for Educators, or anyone else interested in learning more about the Gimp:

The Gimp’s main website, from here you can download the program or its source code:

Wikipedia’s entry about the Gimp. This page contains a number of useful links to Gimp and Digital Image related topics:

The Gimp Manual: This site is an online user manual for the Gimp:

Groking the Gimp: This site is an online version of the book “Groking the Gimp” and acts as a user manual along with some examples and tips:

Meet the Gimp: This site contains video tutorials, podcasts, and other articles that show tricks and tips of digital image editing. It is a wonderful resource!:

The GNU foundation: The Free Software Foundation

Terms used in this article:

FORK: A term that comes from UNIX. To fork means to take one input and split it into two (or more) outputs. Those outputs may then be processed differently to produce two different versions of the same basic input. In open source software, the design of a software package often forks into two different pieces of software based upon a specific user communities needs or desires. The Gimp has a few forks including Cinepaint used in Hollywood to process film, and a version that mimics Photoshop’s user interface.

FOSS: Free Open Source Software. Free as in no cost to purchase or use, also free as in freely available, and freely distributable under public license. Open Source, as in the code used to create the software is open for all to view and modify under a public license.

GIF Image: An older image format for raster images. GIF is a proprietary format but is supported by many software tools. GIF images are limited in the number of colors they may contain but do support transparency. GIF images also support simple frame based animation and can contain multiple frames.

GNU (pronounced G-NOO with no vowel sound between the G and NOO) stands for GNU’s Not Unix and is a kind of Free Software Foundation. GNU created the GNU Public License under which many open source and freeware applications are licensed. GNU is also a big part of the operating system Linux.

JPEG Image: A common digital image format. JPEG images are raster images but do not support transparency. JPEG is a very common image format on the web and almost any software that can work with images supports this format. JPEG images support compression, which means trading file size for image clarity. Smaller file sizes means shorter download times which is why JPEG has become such a popular web image format. Most digital cameras create JPEG images. (file extension .jpg or .jpeg)

Raster Image: A bitmap image made up of pixels on a grid. Each pixel has a coordinate (x,y) and a color value. Some raster images also support transparency, in which case a pixel can also be transparent. Digital photographs are Raster Images. Raster images have a fixed resolution and if scaled image data can be lost or distorted. This is in contrast with Vector images which are more of a mathematical model of an image and are thus able to be scaled dynamically without data loss or distortion. Raster images tend to be less data intensive than Vector images which is why they are more commonly used for photographs.

PNG Image: Stands for Portable Network Graphics. This is another image format that is gaining popularity on the web. PNG images support transparency and layers and can also be compressed to save file size.


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