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Gimp Tutorial at The Bazaar, 1999

A Very Quick Introduction to Gimp

Gimp is a graphics tool. It is not hard to use. Just remember these two simple rules:

The First Rule of the Gimp Club is:

You paint with the left mouse button

The Second Rule of the Gimp Club is:

You select from the menus with the right mousebutton

Many people seem to struggle with the right mousebutton menu for some reason, but you can now step over that pitfall.

Installing Gimp is pretty easy, it uses GNU Autoconf, thus if you are familiar with ./configure, installing Gimp is no problem. Gimp is also included in all of the major Linux distributions. Gimp should also work in pretty much all the common unix systems. More detailed installation instructions can be found in http://www.gimp.org/install_help.html.

Layers

My intention is to help you understand the concept of layers and how to use them in Gimp. This is a bit more advanced tutorial, but it shouldnt be too hard if you are familiar with the very basics of Gimp.

Layers are like a stack of overhead transparencies. You can paint on them and the non-painted areas of a layer will show through anything that is under it. A little illustration will help us understand the concept better:

The layers on the image are partially transparent so you can see the blue layer under the red one. The partial transparency is the thing we are taking advantage of when doing our image.

The Tutorial or 'Brave Attempt to Teach Layers in 3 Hours'

We start by opening a new image - make it 300x400 pixels and select the RGB mode. Also set the default fill to background and check that your background color in the Gimp Toolbox is black. Our image background is black so it is practical to start from a solid black background. Once you have the image in front of you, choose File  Save As and save it as tutorial.xcf. From now on, it is a good practice to press Ctrl-S every now and then to save the work in progress.

Next we need to make a new layer. This layer will be used to make the clouds, so we name it "Clouds". Your Layers dialog should look like the one below. (To open the Layers dialog, press Ctrl-L over your image or select File  Dialogs  Layers & Channels

Then we want to create some clouds. Filters  Render  Plasma is perfect for this purpose. Choose something between 2 and 3 for the Turbulence value. The Clouds layer should now look like a colourful mess of all colors. We dont want these colors in this image, so we merrily select Image  Colors  Desaturate from the menus and we should have a black-and white cloudy image in front of us.

Our sky must not be gray. So we need to colorize this cloud image. Select Image  Colors  Color Balance and select the following values:

Now our cloudy image should be nice and blue. This will make the background for the sky scenery. Your image should now look like the one below:

Now the next step is to make it look more natural. Sky color is usually a bit gradual, in a sunset or sunrise the color is brighter near the horizon and it gets darker away from it.

The easiest way to achieve that is to use a new layer, and have a gradient on it. The idea is to apply a gradient from black on top to white on bottom. Dot this:

• Select white as your background color and black as your foreground color
• Drag a gradient with the Gradient Tool from top to bottom of your image

We then set the layer's mode to Multiply. I called this layer "Sky gradient", you can see it on the image below.

Now you should have a blue sky with some clouds, and the sky should get darker from bottom to up. If you see a black-to-white gradient instead, be sure to check that the layer mode is multiply. See below for a reference image how it should look like.

Stars! The Audience Cries for Stars! Off we go again with a new layer. We shall call it "Stars", and this time lets make it black. To create a black layer set the foreground color to black, and choose foreground fill for the new layer. The image should look completely black at this point.

The Noisify -plugin is a good tool to create a starfield for our image. So we select Filters  Noise  Noisify. The default values are ok, but please uncheck the independent toggle. That controls if we want colored or grayscale noise. In this case we want to avoid color.

You should now have a black image with some noise. It looks a bit like a TV screen that is just displaying the "snow" thing. (Look at the leftmost image below)

Then we want to make the stars brighter, so we select Image  Colors  Contrast Autostretch (Below, right)

Now it starts to look a bit like stars, but there are too many of them. Now, what we want to do here, is to take out most of the small bright dots and leave the most large ones.

We could again use many tools to solve this task, but lets try Image  Colors  Curves. When you first see the dialog, there is a square with a diagonal line accross it from left bottom to top right. Be sure to have the Stars layer selected!

What the curves dialog does? It can be used to adjust the lightness of colors just like adjusting brightness and contrast does, but with more control on what pixels to brighten or darken. We want to darken the gray, less bright dots so only the more bright ones remain visible. Try adjusting the curve yourself, the image shows the preview of how it will look. Look below for how the curve should approximately look like.

Now the layer starts to look a bit like a starfield. You can control the amount of "stars" with the curves adjustment, the more you pull the curve to bottom right, the less stars you get. And vice versa.

Now, we also want to see our clouds in the image. We can accomplish this again by changing the layer mode. This time we want to use Lighten Only since we are only interested in the stars on this layer.

Now it looks like we want. It is quite nice sky background - and we didnt draw a single stroke with the paint tools.

Now I'd like to make the clouds look a bit softer so I use the Gaussian Blur -plugin (Filters  Blur  Gaussian Blur) with the following values: (Dont forget to select the Clouds -layer first!)

(Yes, I had a typo here. Thanks for Csaba and Erik for pointing this out. We definitely want to blur the clouds, not the stars :)

Now it looks even nicer:

Now we have the background in a nice shape. Some mountains wouldnt hurt though. So again, new transparent layer (yes, I love using a lot of layers :) Lets call the layer "Landscape". It should be the topmost layer.

Use the Bezier tool and try to create a landscape form on the bottom part of the image (The bezier tool is the second button on the second row in the toolbox, it looks a bit like an ink pen with a curve) The image below is an example, but your landscape will look very different anyway, and that doesnt matter at all. If you have a hard time working with the tool, you can have a look at my Bezier tool tutorial at http://tigert.gimp.org/gimp/tutorials/.

You can resize the image window a bit larger so you can click outside the image canvas. Once your curve is ok, click inside it to turn it into a selection. Then fill the selection with black color and we have a nice landscape:

Since I am writing this near Christmas time, let us add a nice star to the scenery. Again, one more transparent layer, and we run Filters  Light Effects  Supernova. Set the color to white and the radius to 3. I set the Spokes setting to 59 but you can experiment with that. Just try different values and undo (Ctrl-Z) if you dont like it. You can also alter the color slightly to experiment with the look. If you make the color a bit darker, the plugin seems to generate more spokes.

Many times I have one problem: After I finish the image, and some time passes, it starts to look a bit dull to me. It might be that your eye gets used to it or something. But it happens a lot to me. What we can do, is to add some contrast to the image if we want. Below is a contrast-enchanged version of the image, you tell me if it is better or not.

So here we are with a finished work. It wasnt that hard, was it? Now you should know a bit more about layers and how to use them. Thanks for the interest, I hope you enjoyed this tutorial!

tigert