Our story begins late in the evening, in the halls of an Internet publishing start up: Sherry, working under tight deadlines and unreasonable demands, is sitting in a dimly lit room, trying desperately to integrate some badly-scanned drawings into her Web pages. A knock on the door breaks her concentration. She spins her chair to face the pale faced man she knows only as Gizmo. "What do you want?" she asks.
Our story begins late in the evening, in the halls of an Internet publishing start up: Sherry, working under tight deadlines and unreasonable demands, is sitting in a dimly lit room, trying desperately to integrate some badly-scanned drawings into her Web pages. A knock on the door breaks her concentration. She spins her chair to face the pale faced man she knows only as Gizmo. “What do you want?” she asks.
“Aren’t you done with that page yet?” he answers, “I’ve been done with mine for a couple of hours.”
Her shoulders drop. “No. I’m not done. How’d you get all those images inlined so quickly?”
“The GIMP.” Silence. He stands. She stares.
“What’s the GIMP?”
Get the GIMP
If you haven’t yet gotten your fingers on the GIMP, you have no time to waste. The rest of the Web publishing community is months ahead of you — and saving a bundle on software to boot. What you need is a jump start.
Welcome, friend, to my world.
I live to jump start people, only occasionally resorting to real jumper cables. The GIMP is a personal favorite and I’ve been spouting it’s wonders for over three years now. Let me help you get caught up.
First, you need to grab the GIMP: http://www.gimp.org.
There are two versions you can work with: the stable public release and the unstable developers release. If you’re just starting out, grab the stable public release, 1.0.4. This doesn’t have as many features as the developers release, but it’s stable and has all the basic things you need for this introduction. You also need the GTK 1.2 package from http://www.gtk.org. GTK (GIMP Toolkit) is the code that provides things like buttons, menus, scrolled windows, and lists. It doesn’t say what goes in them, it just provides the basic components for applications to use.
The stable versions of both GIMP and GTK have been around for about six months, so if you have a recent Linux distribution, then you should have both GTK and GIMP 1.0.4installed. Any distribution based on Red Hat 5 or later will probably have the GIMP installed. Red Hat 4.2 users or earlier may need to upgrade.
We’re moving quick, but this is a jump start, not a dissertation. You’ve got the packages; you’ve installed them; you’ve strangled Gizmo for interrupting you four times while you were doing this; and now you’re ready to get familiar with the GIMP itself. So what are the five easy steps?
Step One: The Toolbox
Start the GIMP. You may see it’s smiling dog icon on your desktop, but if you don’t, open an X terminal and type: % gimp.
|Figure 1: The Toolbox.|
Tough, eh. The window that opens will look like Figure 1.That’s the Toolbox. If you have ever seen Adobe’s Photoshop,the two applications look a lot alike. The GIMP’s Toolbox is made up of a series of buttons. Each of these is a core feature of the GIMP. These core features are built into the GIMP, while filters (also called plug-ins) are semi-independent external programs. We’ll talk about filters later.
The core features accessible from the Toolbox include tools for creating selections, drawing and painting, transformations, and text. The GIMP’s drawing and painting features in the 1.0.4 release are a bit limited, but you will still use the Paintbrush, Pencil, Eraser, and Airbrush tools quite often.
Become familiar with the difference between hard-edged and soft-edged brushes (choose the “File-> Dialogs-> Brushes” option). The hard-edged brushes are useful for line drawings, something that is a little difficult in 1.0.4, but not impossible. But when you do this, make sure the spacing option is set to a low value. The usual defaults of 10 or 25 might be too high for line drawings depending on the brush you use. Soft-edged brushes are good for cleaning up the edges of masks and brushing out imperfections.
|Figure 2: Brushes dialog box.|
Brush options are mostly set in the Brushes dialog box (Figure 2), but most of the drawing tools also have Tool Options. Double click on the tool’s icon in the Toolbox to have a look at its Tool Options dialog.
Tools associated with drawing, painting and colors in general occupy the last three rows (not including the black and white boxes at the bottom) of the Toolbox. The kinds of transformations you can do include rotations, scaling, and changing perspective. The transform Tool provides some of these features. There are other possible transforms available via the “Images-> Transform” menu options.
There are three places to access menus: The Toolbox the Image Window (right mouse click opens the menu), and the Layers and Channels dialog (right mouse click on a layer name opens the menu). More on Layers in a bit. The “Images->Transform” menu can be found under the Image Window menu. you’ll want to become familiar with all of these core tools because you’ll eventually use them all.
To jump start yourself, just click on each one and play on a blank canvas. Trust me — you won’t break anything. Made a mistake? Exit and start again. You don’t have to do that, but if you’re confused as to what’s going on, well, then what the heck. Just start over. You’re in class. The teacher won’t mind. And just how do you get a blank canvas? Select “File->New.” Click OK in the dialog window. Could it be any easier? Sure. Ctrl-n in the Toolbox.
Step Two: Selections
Selections are outlines used to limit where an effect or function is to be applied. They are represented by what are called “marching ants,” the small dashed line that appears to travel around the outline. You can create a section with a number of tools from the Toolbox: Rectangular, Elliptical, Freehand, Bezier and Intelligent Scissors. They can also be created using the By Color option in the Selections category of the Image Window menu and through the use of the Alpha To Selection option in the Layers menu.
When you first start out you might not realize how important selections will become. You need to master these to do things like change the background of an existing image, duplicate sections of an image, and draw. Yes, draw. Selections can be “stroked,” which means their outline is traced with the currently selected brush and the current foreground color (the upper left of those two boxes at the bottom of the toolbox is the foreground — guess what the other one is). You can feather selections. This is useful, for example, when you fill in the inside with some color and you want the edges to merge into their surroundings. And what’s really cool — you can selectively apply special effects! If you make a selection, then choose one of the many filters from the Filters menu, it can be applied to just that selected region. Feathered too. Nifty. Bet Gizmo didn’t know that.
Step Three: Layers
|Figure 3: The Layers dialog box.|
Layers (Figure 3) are a way of placing images in a stack and combining their colors (the pixels in each layer) in different ways. If you place a series of transparencies on an overhead projector, with each transparency colored differently, you’ll get an image displayed that is the composite of those transparencies. Layers work just like that, except that you can specify, through their individual layer modes, how each layer is to be combined with the layers below it. The layer modes include Multiply, Screen, and Overlay (which darken, lighten and something-in-between the layers, respectively), Difference and Subtract (similar functions but with potentially different results), Addition, and a bunch of others.
Why learn about layer modes? Want to generate 3D effects? Blur one layer to differentiate it from another. It does not work in every case, but that’s basically how simple 3D buttons and text get started. And by changing just the modes, you change the effects without changing the pixels in each layer. This is important: Changes to pixels are hard to get back. Yes, yes, GIMP has an Undo feature (Ctrl-z) which will undo the last operation performed. But sometimes you don’t know you want it undone till you’ve gone way past the number of operations that GIMP will remember.
Here’s a better solution: Use non-destructive methods wherever possible. Layers and layer modes fit this bill just perfectly. Ok, we’re moving really well now.
Step Four: Filters
Now this is the fun part. You can paint stuff. You can select stuff. You can even combine variations on your painted and selected stuff. “But Mike,” you ask as you pour
honey over Gizmo, “What about all those cool distorted images we’ve seen on your Web pages? How do I do that?” Filters. Plug-ins. Call them what you want, they are the set of tools found under the Filters menu that do all manner of grunging to your images: blurring, warping, twisting, sparkling, and even bumping. You can add sun bursts, reflections, and flames. And unlike cigarettes, smoke from filters is not a bad thing. No, not real smoke. Rendered (re: generated) smoke. It starts with “Filters->Render->Plasma.” Honest.
So how do you use these? There’s just no generic way to describe this. The filters are bundled into subcategories, which helps. The set of blur filters all work on the currently selected layer. They won’t go past the selected region (unless your selection is feathered) or edges of the layer, however. Motion blur is fun — give that a try on some image.
The Artistic filters do just what they say — apply some generally well known artistic effects to a layer or selection. My favorite is GIMPressionist. This one isn’t included with the 1.0.4 release — you’ll have to find it via
the Plug-In Registry (http://registry.gimp.org). But wait on that till you’re comfortable compiling software. If you’re not familiar with that yet, well you might want to get Gizmo a wet towel and help him clean up.
Except for the Render subcategory, the filters all apply some effect to the existing image by changing the pixels in that image. You want to hang on to the original, duplicate the layer first, and work on the copy. Munge the colors with “Image-> Colors->Curves.” Then apply another filter. Back and forth. Over and over. The Render sub-category is different. Those filters generate something completely new, not based on the current layer or image. These are very creative tools. Flame, QBist and IFSCompose are a couple of my favorites here. The interesting thing about filters is that you’ll find them fun and creative, but most of your work will actually be with the basic core tools, and you’ll probably do a lot of work with the “Image->Colors” menu options. Because color is such a technical subject I left it out here. I wouldn’t worry too much.
Gizmo only works in black and white. I’ve seen his work. Bleck.
One of the things we didn’t get into here was layer masks. Remember what I said before? Try to be non-destructive. If you have an original, make a duplicate layer first, then run it through filters. Layer masks are extremely useful because they allow you to remove pixels without actually removing pixels. How? They mask out the unwanted pixels from the visual display. You edit the mask to change your image, but you leave the original pixels alone. Non-destructive. As the saying goes: ‘Tis easier to destroy than to create. Or recreate. You get the point.
Step Five: Do Something Useful
So now what? Those were only four easy steps.
|Figure 4: How about a logo?|
Step 5: Do Something Useful! Let’s start easy. How about a logo? Use the predefined logo scripts — Xtns-> Script Fu->Logos. Try “Chrome.” Does it work? It should look something like Figure 4. If not, you might not have the default font (which is listed as “bodoni”) installed. No problem. Try it again and specify another font, say “fixed.” The biggest problem people have with these canned logos is that they use fonts that the users don’t have installed. Common problem. There is an easy fix — just change the font to one you do have. All Unix boxes have the “fixed” font.
Something else? Try this:
3. Open the “Image->Levels” dialog.
4. Under the histogram is a bar that runs from black to white with three little triangles under it. Move the left (black) triangle to the right about half way.
5. See where it says Value at the top of the dialog? Click on it, and select Red from the menu that is displayed.
6. Adjust the black triangle to the middle again.
7. Select Green from that menu.
8. Slide the gray (middle) triangle towards the left a little.
9. Select Blue from that menu.
10. Slide one of the sliders around.
|Figure 5: GIMP’s blazing filter.|
It should be a bit fiery red now. Maybe with some yellow tints to it (See Figure 5).
Play with the sliders for each of the different colors in that menu. You’ll eventually get that look of flames. All with nothing more than a little desaturated plasma and some coloring with the Levels dialog. Pretty cool, eh?
If you need to find more information, there are a couple of printed texts on the GIMP now, including one I did (hint hint, wink wink). Both are targeted at new users so if you want or need printed documentation, these are good places to start. There is also a very large online document called GUM (GIMP User Manual). You can download it, but it’s quite a hefty download. Online, it lives at http://manual.gimp.org. For other information, start with the GIMP’s main Web site: http://www.gimp.org. There are links there to other online information, plus this is where you will find the mirror sites for downloading. You can find a list of online tutorials at http://empyrean.lib.ndsu.nodak.edu/~nem/ gimp/tuts/.
Michael Hammel is the author of Artists Guide to the Gimp. He can be reached at email@example.com.
Michael J. Hammel
(http://www.graphics-muse.org) is a Principal Software Engineer for Colorado Engineering, Inc. (CEI) in Colorado Springs, CO, with over 20 years of software design and development experience. He has written more than 100 articles for numerous online and print magazines and is the author of three books on the GIMP, the premier open source graphics editing package. He is currently working on a MythTV front end design suitable for use with an outdoor DIY projector for summertime movie watching.