You've decided to learn to edit images with GIMP! But if it's not already on your computer, first you have to install it.
You may have Windows, Linux, a Mac, or another UNIX system such as FreeBSD. All of them can run GIMP, but each has a different installation method. Of course, if you can, you'd certainly prefer to run the most recent 2.4 version. Most computers can, but some OS variants are too old. If that's the case, you may have to run an older version. We'll explain those options in Appendix B. If you wish, you can also build GIMP from source, which is covered in Appendix C.
Here, you'll learn
Requirements
Where to find GIMP
Then skip to the appropriate section:
Installing on Windows
Installing on Mac
Installing on Linux or UNIX
GIMP doesn't require an especially fast machine. However, if you want to work with large images, you'll find that more memory will help a lot. A faster processor won't hurt, of course.
On Windows, GIMP 2.4 should work on NT4, Windows 2000, XP, or Vista. If you have an older version of Windows, skip to Appendix B.
You can download GIMP 2.4 for Mac OS X Tiger (10.4) or Leopard (10.5). The more adventurous Panther (10.3) users can also build GIMP 2.4 using the MacPorts system, but it's probably easier to just download GIMP 2.2 as Gimp.app from http://gimp-app.sourceforge.net. OS X systems older than Panther face other problems (see Appendix B). If you have OS 9.2 or earlier, you cannot run GIMP at all; it was never supported and never will be.
Recent Linux and other UNIX-based systems will have GIMP 2.4 in their packaging system, and it may very well have been part of your initial installation; you probably already have it.
On UNIX-based systems (including Mac OS X and Linux), GIMP is also an "X" application: it's built on top of a toolkit called GTK+ that uses the X Window System (sometimes called X11 since most systems use version 11) for drawing to the screen, creating windows, and other low-level operations. X doesn't stand for anything except "the next letter after W." (Seriously! X was the successor to a window system called W, which was in use at MIT in 1984 when X was being designed.)
So you'll need X in order to run GIMP. This is only likely to be an issue on Macs, since most Linux and UNIX systems are already running X. (There's a version of GTK+ in the works that will run on OS X without requiring X, but it's still experimental. If you want to try a GIMP built on the Mac-native GTK, you may be able to find builds at http://gimp-app.sourceforge.net.)
One thing you shouldn't need is money. GIMP is free software: free because you can get it without paying, and also because you're free to redistribute it or modify it.
You can buy GIMP from various sources, and sometimes these versions include extra goodies like an installer or a collection of cool brushes. But most of the time, you'll do just as well starting with the free version.
The GIMP project lives at http://gimp.org. There, you can find links to downloadable versions for several operating systems along with instructions on how to get GIMP for even more systems. You can also find out how to build it yourself if you want to try the latest cutting-edge version.
At gimp.org, you'll also find a substantial collection of documentation. There's a complete user's manual, a large collection of tutorials, and information on GIMP's programming interfaces for anyone interested in writing scripts or plug-ins. You can sample a collection of mailing lists and IRC channels where you can ask questions, volunteer to help, or just trade tips.
Please remember that any URLs listed here may change. The web is beyond our control!
Unlike previous versions, installing GIMP 2.4 on Windows is very much like installing any other software (except you don't have to pay for it). The only tricky part is Python. If you want GIMP to be able to run Python scripts, you'll need PyGTK (from http://pygtk.org) plus all its dependencies. Getting them all to work can be somewhat challenging on Windows (it might be easier to install Linux!).
First, navigate your browser to http://gimp.org. The opening page will have a Download button right in the title bar. Click that and you'll probably be taken to the Windows Download Page automatically (gimp.org tries to figure out what system you're using). The first link should be the Installer, which you download.
When the download is finished, double-click the EXE file to expand it and get to the installation window. First you'll see a typical Welcome screen. Click Next to get going. You'll then be given an opportunity to read the GNU General Public License—the GPL you may have heard about. When you've had enough, just click Next again and you're at the Install page.
Your options are Install now (which is fine) or Customize. If you choose the latter, you can indicate an installation folder that's different from the default, choose which components to install, indicate which file types should launch GIMP, choose your Start Menu folder, and indicate if you should have a desktop icon and/or a Quick Launch icon. Generally, you won't want to change any of this, but if you do, then Customize is your best option.
Either way, you'll end up clicking an Install button and eventually get a screen that tells you the installation is complete and offers the option to launch GIMP (the default has a checkmark beside it).
You can delete the installation EXE now if you wish. You're done!
Before downloading GIMP 2.4, make sure you have X11 installed (or optionally XQuartz on 10.5 Leopard). If it's already on your system, it should be in the Utilities subdirectory of your Applications folder. If it's not already there, you can install it from your System Install disc. Can't find your old discs? Download the appropriate version from Apple using your Mac OS X Software... finder menu option. X11 will be in the Unix & Open Source section. (Leopard users may be able to get GIMP 2.4 there too!)
Point your browser to
http://gimp.org, click on Mac OS X to go to the Wilber Loves Apple site, and get the proper version for your machine.Double-click the DMG to mount it, then copy GIMP 2.4 to your Applications folder. Start it as you would any other application (it will automagically start X11 for you if it's not already running).
The GIMP project doesn't provide Mac builds (or, indeed, builds for any system), but works with another organization: the Wilber Loves Apple community. If you start at gimp.org and click on Mac OS X, it takes you to their site: http://darwingimp.sourceforge.net.
You'll be faced with four possibilities: OS X 10.5 (Leopard) or OS X 10.4 (Tiger), Intel, or PowerPC? Surely you know! But if you don't, both questions are easily answered by going to the first item in your Apple menu, About This Mac. The Version line will say 10.4.something (Tiger) or 10.5.something (Leopard). The Processor line will list either a PowerPC or an Intel chip.
Note
If About This Mac says 10.3.something (that's Panther) or earlier, you're out of luck in this section and should proceed to Appendix B. Or you can upgrade your system. Your call.
Download the correct version. Go to your usual download destination and double-click the Gimp2.4.blah.blah.dmg as you normally would. This will mount a virtual disk and open a window with the GIMP application in it...and one other thing: the GNU Public License. What you do with the latter is up to you, but the former should be copied to your Applications folder. This may take some time since it's a fairly big file.
Once that's complete, you can double-click the Gimp (not all caps!) icon to start the application. It has some housekeeping to do on first startup, so it might take a while. Subsequent starts will be much faster.
If all went well, you can unmount the Gimp virtual disk and trash the DMG file. That's all there is to it!
Of course, you'll need to be running X to use GIMP, but you probably are. If you're running any programs that involve a mouse, you probably have X. Also, most distributions will have already installed GIMP for you. Type which gimp at the command line, and if you don't see something like gimp: command not found then you already have it.
What if you don't have it? Don't bother with gimp.org in that event—they'll just tell you to install the packages supplied by your distribution. Really, that's the best idea.
Using the package management system of your distribution, install GIMP.
There is no #2.
If you haven't yet used your package management system to install software, here are some common ways to go about it on various systems. Most systems have more than one way to install packages, including user-friendly Install new software entries in the system menus; but failing that, here are some popular command-line methods that are known to work.
You'll have to gain root access to use these commands either by using sudo or su.
If your distribution is older and includes a previous version of GIMP, there are two reasonable options: either install and use the older version or upgrade your system with a newer version of your distribution. While it is possible to build GIMP 2.4 for some older systems (see Appendix C), it's almost always better just to keep the system and software in sync.
Fedora and Red Hat users, type:
yum install gimpDebian, Ubuntu, and other Debian derivatives, type:
apt-get install gimpOpenSUSE users, type:
yast -i gimpMandriva users, type:
urpmi gimpGentoo users, type:
emerge -va gimpFreeBSD users, type:
pkg_add -r gimp
While you're at it, check to see whether there are any other GIMP-related packages you might want to install. Many distributions offer packages for some of the more popular plug-ins, like xsane (for scanning), gap (for animations), ufraw (for reading raw images), and so on. GIMP's online help files are also often packaged separately. You might also want the "development" package, named something like gimp-devel or libgimp2.0-dev, if you want to install more plug-ins or write your own. Ubuntu or Debian users, type aptitude search gimp; Fedora users, type: yum list available | grep gimp; SUSE users, type zypper search gimp; and Gentoo users, type emerge -spv gimp.
That's all there is to it. Your system should take care of everything else for you.
Of course, there are far more Linux and UNIX variants than can be listed here. The rest of you are on your own!