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Getting Started with The GIMP

© 2010 SF Kinney, Released under CC BY-NC 3.0 License
http://creativecommons.org/licenses/by-nc/3.0/

GIMP 2.6

The GNU Image Manipulation Program (originally the "General Image Manipulation Program") is a powerful photo editing and image authoring tool for personal and professional use. Developed by volunteers and licensed under the GNU Public License (GPL), the GIMP belongs to you. Descendants of the GIMP will go to the stars with us. It has already gone to Hollywood: The Film GIMP a.k.a. CinePaint has been used extensively in motion picture processing - and CinePaint is also Free Software in case you are interested.

The GIMP is included by default in most Linux distributions, or get it with your package manager. For MS Windows, see below. GIMP for MAC OSX at gimp.org provides Apple details.

Installing GIMP 2.x on Windows

You will need two installers when you get the GIMP for Windows: The GIMP, and the GIMP Help files. Download them from http://www.gimp.org/downloads/. Once you have them, install the GIMP then the GIMP Help files. The “terms and conditions” you must click to agree to are the GPL, which means that the software is Free and that you already (non-exclusively) own it. During installation the GIMP will ask you if you want to associate any file types with it; the answer is yes, but only the XCF file extension. When you are done, you will have an icon for the GIMP on your desktop and a program start menu entry – if you selected these options when asked. The first time you run the GIMP, it will create its configuration files and will ask you if you want to calibrate the scale of your monitor. You can do this or skip it, either way the GIMP will work fine. Throughout installation, select default options: You can change them later if required.

Warning! Do not download the GIMP from unofficial websites offering "Free Downloads." Sabotaged GIMP installers rigged with trojans have been discovered in the wild. Sourceforge.org, formerly a trustworthy repository for Free Software including the GIMP for Windows, has new owners with no particular ethical stance against saboage: Steer clear.

Welcome to X-Windows

The windowing and menu systems in the GIMP may initially be confusing to MS Windows (and Mac) users, because the GIMP uses the GTK (GIMP Toolkit) menu system native to X-Windows for UNIX: Instead of putting one big box on the screen and anchoring everything inside it, the GIMP puts different components in their own independent boxes, which can be moved around freely on the screen – or closed when not needed. The fastest way to access menus when editing an image is to right-click the image, which opens a context menu on the spot. When you need to dig down to the same menu item repeatedly, despair not: Click on the dotted line at the top of the menu with the command you want, and it "tears off" as a floating menu box that can be moved anywhere on the screen, and stays open until you close it. The window system used by the GIMP was designed for efficiency; it opens up lots of screen space, and save miles of mouse movement.

GIMP 3 Is Coming!

GIMP 2.8 Splash Screen

If you just downloaded the GIMP, you have GIMP 2.8 which is one version "higher" than the one this introduction was originally written for. GIMP 2.8 includes many changes and improvements and I have updated this tutorial to reflect these changes. Version 2.8 will be followed by version 2.10 then GIMP 3, introducing a new high-resolution color model that has taken years to develop. Since I use the GIMP for production work, I put off upgrading to 2.8 for months, but the new OS on my main workstation (Mint 14) includes GIMP 2.8, and I am quite pleased with it.

Only a few changes in GIMP 2.8 have a major impact on the present tutorial: It is now easier to find the menu for adding and removing buttons from the main toolbox (see below), and the "Save" command now saves images in the GIMP's own .xcf file format. To save an image as a .jpg, .png, etc, use the "Export" command (or ctrl-e). This new file saving behavior set off a firestorm of complaints from users: At first it was funny but now it's just tiresome. Making Save and Export separate commands reflects the way professional users have always done things; it's a minor convenience for us, a minor annoyance for some others.

GIMP 2.8 also introduces a much asked for option to configure the GIMP to appear as "one big window" that occupies the whole desktop. Fortunately for folks like me, this configuration is an option that can be turned on and off at will. Far be it from me to complain about "freedom of choice" for users of Free Software: Test drive the "normal" and "single window" modes and see which one you prefer.

Suggested GIMP Configuration

GIMP toolbox

The first time you run the GIMP, it will open four windows. On top will be a "tip of the day", which you can disable when you get tired of it. You will also see the main toolbox window, the one with the field of buttons at the top (see right). This is your "keeper", and it will live on the right or left side of your monitor screen, according to personal preference. There will be an empty image window, ready to drag and drop pictures into. Finally, there is a redundant "dock" with space for multiple tabs like the ones in the bottom half of the toolbox as shown here. I would ignore & close that extra dock.

The current online GIMP manual features a picture with the redundant dock window open, and says that this is “the most basic arrangement of GIMP windows that can be used effectively”. That's simply wrong. Having 8 to 12 more square inches of screen space for the image content I am working on is more effective for me, so I set up the main toolbox to include everything used for common image editing tasks.

You can resize the toolbox by clicking and dragging the edges; I normally keep mine 7 buttons wide, and one screen tall. You can add buttons to the main toolbox menu, and you definitely should. Go to Edit > Preferences > Toolbox, and make sure that the Hue/Saturation, Brightness/Contrast, Threshold and Levels buttons are turned on. These are frequently used tools that are otherwise buried in the Colors menu. You may want to turn some buttons off, the configuration shown here omits some default ones that I seldom or never use. Your choices may vary.

You can add tabs to the dock area below the buttons on the main toolbar: Click on the tiny left-pointing arrow at the right side of the tab area, and make sure that these are all turned on:

Layers, Tool Options, Paths, Undo History, Channels, Brushes

In the main menu under Windows, the Recently Closed Docks item will enable you to easily identify and bring back any windows you have previously dismissed; in the same menu, Single Window Mode toggles between single and multiple windows. There is also a Dockable Dialogs menu in the Windows dialog, for opening any of the dialog items, which can be used as stand alone items or dragged and dropped into your dock of choice.

There is no one "right way" to configure the GIMP: For instance, if you are using the GIMP to do digital painting with a tablet and stylus, you might find having an always-open dock for your brushes and palettes essential. If you use dual monitors, it might be beneficial to have a lot of menus and docks open on one screen. The configuraton shown above is a good starting point for new users, and very efficient for photo editing tasks. But as usual with Free Software, you can customize the GIMP in numerous ways to suit your own needs and preferences.

One of the more important things to tweak early on, is to set up the GIMP so that holding the ALT key down and scrolling your mouse wheel will make brushes larger or smaller on demand. Go to Edit > Preferences > Input Controllers and double click on Main Mouse Wheel to bring up the configuration dialog. Picture worth thousand words: mouse-scale-brush.jpg. I think this setting should be a "default" - but meanwhile, you can set it up yourself. I also configure the GIMP to make the current brush "softer" or "harder" - that is, more or less fuzzy around the edge - in response to holding down Ctrl + Shift + Alt and scrolling the mouse wheel up and down. Controlling brush size and hardness with the mouse wheel is way more efficient than constantly switching between brushes.

The main Preferences menu in the GIMP is important. It lives at Edit > Preferences, and has lots of sub-menus. Under Appearance, "Default Appearance in Normal Mode", you can choose whether or not to display a menu bar across the top of the image editing window. I always turn this off: You can right-click the open image (or blank image window) to get the same menu when you need it. In the Interface menu, set your Preview size to Large, unless you have a tiny monitor. Under Environment, select whether to display a tool icon next to your cursor when you are using a drawing tool, to remind you which one you have turned on; you probably want to turn this off by selecting "Crosshair only". You do want to see the Tool Outline, however! You can customize a lot more in the Preferences menu.

Getting Help

When you have the GIMP configured as described above, you are all set to dive in. Make sure you know how to use the GIMP help files. Every filter dialog has a "Help" button that provides a useful explanation of what the filter does and how to use its settings. You can also select Help > Context Help in the main menu, then click anything with the ? cursor to get the help file for the tool, button, or whatever in question. The entire GIMP Help documentation also lives here: http://docs.gimp.org/2.8/en/.

Zooming Around

You may have noticed that the "magnifying glass" tool button is turned off in the GIMP toolbox shown above. That's because it's much faster and easier to zoom around inside images using the keyboard and mouse only. Try it out: Open up the GIMP and drag and drop a picture into the image window. Try these commands with your keyboard and mouse wheel: If you do start using the GIMP regularly , moving around this way will become a reflex:

  • Ctrl + scroll up/down to zoom the image in/out
  • Shift + scroll up/down to move the image left/right
  • scroll up/down to move the image up/down

Zoom way in on part of your image, and look for the little four-pointed arrow at the lower right corner of your image window. Click and drag on that arrow to see what happens: This is the quick way to move around inside a big picture, and note that you can scroll past the edges of the image, making it easier to work on them. Always remember: If you are having trouble getting precise results with a paintbrush or other drawing or selection tool, you can zoom in closer! Press the number "1" on your keyboard to instantly zoom your image to normal (1:1) size.

You can go to full screen edit mode by pressing F11, and back to normal by pressing F11 again. The tab key will toggle visibility of the toolbox off and on, so you can preview images or even work on them in full screen mode without the toolbox in your way.

Working With Layers

Layers are the key to advanced image editing: Almost every image an expert user is working on becomes a stack of layers, each containing a different part of the work in progress. Layer modes, selected from the drop down menu at the top of the Layers tab, control how a layer affects the appearance of the layers below it and so, the final product of the editing process. The transparency of a layer can be adjusted, for instance to reduce the amount of change a filter used on the layer causes in the final image: In routine post exposure work I often deliberately "overdo" color and light adjustments on a layer copy of the original image, then "dial back" the result to something more natural looking by adjusting the opacity of the altered layer until the result looks "just right".

GIMP Layers Explained

Layer masks are very powerful tools: They turn the layer you are working on into a stencil, with only the parts you want to see showing through in the finished image. In the GIMP layers dialog shown here, a black and white image has been colorized and put on a new background by using layer masks: The first (lowest) layer was made using effects in the Render and Distort menus. The second layer is a Sample Colorized version of a black and white image I got from subgenius.com, with a layer mask added that makes the background invisible to let the colorful layer below show through. The third layer is the original black and white version of "Bob", with a layer mask that is mostly black (= transparency), but painted white (= visible) to make the Pipe, Grin, eyes and hair visible in black and white in the finished image. I created the top layer in the illustration just to show you what the finished product looks like. This is only the beginning of what can be done with masks and layers. The GIMP online help docs introduce Layer commands in Section 7.21

The GIMP .xcf file format: Save early, save often

Whenever you start to work on an image in the GIMP, the first thing to do is save the file as an .xcf file. That is the GIMP's native file format. XCF saves all layers, layer masks, selection areas, channels, guide lines, text layers, and vector paths. Since .xcf uses lossless compression, it is safe to edit and save an .xcf file over and over again. (Lossy compressed files, such as the jpg format, deteriorate when saved, reopened, and re- saved.) When you are done with your editing, save your work (Ctrl + s ), then export it in the format you need for your finished product. Your saved xcf file is your "definitive archive copy" of the image. It enables you to pick up where you left off and make more changes if necessary, with no loss of resolution and all your layers, masks, paths, dynamic text, etc. intact and ready to use.

As noted above, the GIMP 2.8 command to save files in formats other than .xcf is "Export", not "Save." The GIMP "Saves" drafts of work in progress, and "Exports" images as finished products for use in documents, web pages, print layouts, etc. Use the menu command File > Export, or the keyboard shortcut Ctrl + e. When you export a file, the GIMP will recognize the file type from the extension you type when you name it, i.e. .jpg, .png, etc., and will present a dialog for configuring all the options that apply to the file you are creating. You can accept the default settings or adjust compression, add a comment field, etc. as applicable. Information about image file formats and how they are used can be found in chapter six of the online GIMP user manual.

Where to Go Next

The best GIMP tutorial I have seen is Really Basic Photo Editing with the GIMP by Matt McIrvin. The original site is gone, but the tutorial lives on in the mighty Wayback Machine at archive.org. Matt introduces many useful methods beginners should learn early, and explains the most frequently used techniques for improving digital photos. Note that when the tutorial was written, an earlier version of the GIMP was current. Don't be too concerned when a menu item is not exactly where he says it is, or a filter dialog does not look exactly like yours. The differences are small and you will find your way around easily enough.

The GIMP User Manual online version includes a very good introductory tutorial starting in section 4, Common Tasks, that is well worth reading. You will learn about how to use the GIMP for simple image editing, and some image file fundamentals for real-world applications like web display and color printing.

GIMP Magazine is a new resource for GIMP users that you don't want to miss: As of this writing there are three issues available, free to download in PDF format. The list of links to online GIMP resources provided in issue number one is really outstanding. Get on over there and get majorly inspired!

GIMP Paint Studio is a large set of GIMP brushes, tool presets, and other optional tools developed for people who "paint" with the GIMP. Remarkably realistic pencil, pen, crayon and brush effects, smudging and blending tools, and more are provided for those whose canvas is a tablet. (I use a few of them too.)

In response to a question on the gimp-user list, I have made a tutorial on how to make drop shadows in the GIMP. This one includes rendering a pattern and using it to make a mask that simulates the zig-zag edge of a patch of cloth that has been cut with pinking shears. Using layer masks to make drop shadows is easier done than said - so I have illustrated every step with screen shots.

Note: The graven image of J.R. "Bob" Dobbs is a registered trademark of the SubGenius Foundation and may not be used without the express written permission of the Foundation or Rev. Ivan Stang, but I did it anyway.