Introduction to the GIMP

This isn’t an SL/IW/OS tutorial as such, but if you’ve never done much GIMP before, then this will show you how to use some of the tools and start to take the mystery out of the interface. By the time you get to the end, you should have an image that looks something like this.

I am assuming that you have downloaded and installed the GIMP and of not then you’ll need to go to the web site, www.gimp.org and do so.

Conventions used in this tutorial

Menus accessed with the Mouse are described in the format:  Menu => Sub-Menu => Option
For example:  Filters => Render => Pattern => Grid

Keyboard short cuts are a much faster way of getting the job done.
They are shown in Bold Type and inside parentheses, for example: (CTRL + C).
Don’t type the brackets, just the key strokes.

If the images are not big enough to read the labels or settings, try clicking on them, most if not all of them will show the full size image, you can then use your back button to return to this page and keep working.

The Gimp’s Windows

The first time you fire up The Gimp you will probably see two separate windows, the Toolbox and the Image Window (currently empty), like this:

This is completely normal, it’s how the Gimp’s interface is intended to work. I found it very off-putting at first because I was expecting everything to be captured inside one window like in photoshop or paintshop or something. But it didn’t take long for the flexibility of this approach to become readily apparent and to be perfectly honest, there’s no way I’d trade this for anything else now.

You’ll also find it useful to have the Layers dialogue showing, you can bring this up from the Image Window by going:
Windows => Dockable Dialogues => Layers (CTRL+L)

Rather than bore you rigid with an exploration and explanation of all the tools, dialogues, options and intricacies, let’s get straight on and DO something.


A first Gimp Image

1. Create a New Image, 800 x 600 pixels.

File => New    (CTRL + N)

When the dialogue comes up you can choose 800 x 600 in the Template List or type the values you want into the Width and Height fields.

SAVE this now using File => Save (CTRL+S) and call it boat_scene.xcf The .xcf format is GIMP’s native format (like MS Word documents are .doc and Notepad documents are .txt). It is important to save your work in the .xcf format because it preserves things like the layers and text so that you can return to it later and make alterations. If you don’t know what that means, don’t worry, you soon will do. And if you’re thinking “what’s this xcf nonsense? Every one knows that you use jpg or png for the web and tga for SL etc”, don’t worry, we will talk about that later too. But for now, trust me. Save your work as we go and use the xcf format.

Please remember to save your work regularly as you go along. I don’t want to hear any cries of despair because someone lost an hour’s work because the system crashed, the power went down or the puppy chewed through the keyboard cable. Press CTRL+S regularly as you work and keep your changes safe.

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2. Choose the Rectangle Select Tool (R) from the Toolbox

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3. Drag a rectangular box around the lower half (roughly) of the canvas in the Image Window, .

You should then have a Marquee (a sort of moving dotted line that looks like ants marching) around the lower half of your image.

You can click and hold your mouse inside those purple squares and drag them around to fine-tune the selection if you need to, but don’t worry, it doesn’t have to be exact.

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4. Select Foreground and Background colours.
Back in the Toolbox the pair of overlapping squares are the colour selectors, the top one is the foreground. Click on it to bring up the Colour Change Window.
Choose an orange-ish colour for the Foreground colour.

Now click on the background colour selector and repeat the process to choose a blue colour for the Background colour.

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5. Select the Blend (or gradient) tool from the Toolbox window (L) and check that:

  1. The Blend Mode is Normal
  2. The Gradient is set to FG to BG (RGB)
  3. The Shape is set to Linear.

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6. Paint in the gradient.
In the image window, hold the mouse in the upper middle part of the selection, drag it down to the bottom and let go.

You should end up with something like this.

If it doesn’t turn out how you expected or wanted, you can undo the action (CTRL+Z) and try again.
It is worth experimenting with angling the line that you drag for the Blend Tool and also starting to drag from above the marquee until you get something that you like.

Save your work. (CTRL+S)

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7. Using the Ellipse Select Tool (E) from the Tool Box, drag a circular shape such that the upper half of the circle is over the white area of your background and the lower half is over the coloured area.

You don’t have to get a perfect circle, but if you want one, hold down the SHIFT key as you drag the mouse.
If the marquee doesn’t end up exactly where you wanted it, you have a couple of options to fix it:
1. Image Window => Select => None (CTRL+SHIFT+A) – and then try again.
2. Put the mouse cursor inside the marquee and click and drag it into position.

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8. Choose the Rectangle Select Tool from the Toolbox. Make sure that the tool is set to Subtract from the current selection.
Drag the box so that it covers the top half of the elliptical Marquee.

Now Copy and Paste (CTRL+C) then (CTRL+V) the Selection. You will see that a new layer appears in your layers window.

Actually, it isn’t strictly a new Layer (yet). In the Layers window it is called “Floating Selection (Pasted Layer)”.  Click on the New Layer button (highlighted in the screen shot above) so that it becomes a proper new Layer – its name changes to Pasted Layer.

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9. Select the Move Tool (M) from the Toolbox, make sure the Pasted Layer is selected in the Layers window and drag the pasted layer up into the white part of the background.

It would be a good idea to rename the pasted layer to something more meaningful. Before long we’ll be pasting another layer and the names quickly become repetitive and meaningless. In the Layers window, double-click on the name of the layer, type: Sun and Hit Enter.

Back in the Image Window (with the Sun Layer still selected in the Layers Window) go to the Layer Menu and flip the Sun Layer vertically.
Layer => Transform => Flip Vertically

You can now use your Move Tool (M) again to line the Sun layer up with the Horizon.

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10. The Free Select Tool (F), often referred to as the Lasso Tool, allows you to make freehand selections.
Select the Background Layer and use the Lasso to make a selection that looks something like the one below.

Hints:

  • To get the selection to go exactly around the outside edge of the image, drag the Lasso outside the image.
  • If you take the end of the selection up VERY close to the beginning, it will close the selection automatically when you release the mouse button. But, if you are too far away, you end up with one or more little round Handles, as illustrated below.

  • If this is the case, move the mouse into the Handle at the beginning of the selection and let go, it will then complete the selection.
  • Keep an eye on the Status Bar at the bottom of the Image Window, the Gimp will be trying to give you hints about how the tools work.

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11. Copy and Paste the selection, so that you have a new “Floating selection as before.

Make the Floating Selection into a New Layer and rename it to: Highlights.

In the Layers Window, set the Highlights Layer’s Mode to Overlay.

You may also wish to lower the Opacity setting somewhat to get a more subtle effect. In the illustration below, you can see that I used the slider in the Layers window to set the opacity to 50% for the Highlights layer.

You could also choose a different Layer Mode and experiment with the settings.
(Setting the Layer Mode to Dodge and reducing the Opacity a lot, also works well.)

Anyone saved their work recently…?

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12. Choose the Fuzzy Select tool (U) from the Toolbox (it looks like a Magic Wand), set the Background as the Active Layer in the Layers window and click inside the white area of your Image Window. This should select the sky area.

Choose suitable Foreground and Background Colours and use the Blend tool to paint the sky.

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13. Feeling Artistic?
Select the Airbrush Tool (A) in the Tool box, set the Brush Type to ‘Fuzzy Circle’ and set the Foreground colour to a white or off-white colour.
Use the Airbrush to rough out some cloud shapes in the sky.

They look pretty horrible at the moment so switch to the Smudge Tool (S), you may want to switchback to a hard edged brush too, and blend and soften your clouds.

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14. Open the following image directly into your GIMP:

File => Open Location => paste in the URL

Experiment with the Magic Wand (U), the Blend Tool (B) and the Bucket Fill Tool (SHIFT+B) to fill in the hull, mast and sails with colour, gradients or patterns.

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15. Resize the sail boat picture

Image => Scale Image
Set the Width to something like 150 pixels. You need not worry about the Height setting because as long as the little chain icon is intact it will scale the height in proportion to the width automatically.

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16. Paste it into the main image.

Use the Magic Wand (U) to select all of the white background and then Invert this selection
Select => Invert
(CTRL+I)

Note how the marquee is around the parts of the boat and the outside of the image in the first picture, but only around the boat in the second.

Copy the sail boat that you just selected using CTRL+C and paste it (CTRL+V) into the main image.

Change the Floating Selection to a New Layer and rename it to sail boat.

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17. Duplicate the sail boat layer (CTRL+SHIFT+D)
(there is also a button at the bottom of the Layers Window to do this).

Rename the layer: sailboat reflection.

Flip the sailboat reflection layer vertically

and move it down into position beneath the original sail boat layer

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18. Creating the Reflection

Experiment with the following tools to manipulate your sailboat reflection layer:

  • Move Tool (M)
  • Rotate Tool (SHIFT+R)
  • Scale Tool (SHIFT+T)
  • Shear Tool (SHIFT+S)
  • Perspective Tool (SHIFT+P)

All of these tools will allow you to make freehand adjustments and some will also allow you to type values into the dialogue boxes.

In the example below, I am adjusting the Perspective by dragging the little square handles around.
The Perspective tool shows what will be the result of the transformation overlaid with the original, when you hit the Transform button in the dialogue, the transformation is made and the original disappears.

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19. Adjust the opacity of the sailboat reflection layer using the slider in the layers window.

You may also wish to lower the reflection layer so that it is behind the sailboat layer, use the little arrows beneath the Layers to move the layers in relation to each other.

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20. SAVE YOUR IMAGE

You were saving this as you went along, weren’t you?

Save this final version of your boat_scene.xcf

As I said earlier it is almost always worth saving a copy of your image in the Gimp’s native format because it preserves the various layers and paths so that you can come back and work on it easily later. You can also copy layers or text out of it, of it for use elsewhere.

But you will also need to save it in a format suitable for wherever you wish it to be used or displayed.

The most commonly used formats for the web are PNG (Portable Network Graphics) or JPEG (Joint Pohotographic Experts Group). PNG is the more modern format and is designed to replace both JPEG (and another format called GIF, that you may know). But, I usually use JPEG for my web sites because the file sizes are generally smaller than they are with PNG.

If I was going to upload it into SL/IW/OS, I would use a different format altogether, I’d use TGA (Truevision Advanced Raster Graphics Adapter) better known as TARGA format, but you could also use PNG. (But JPEG is not recommended.)

Do a File => Save As (CTRL+SHFT+S) to save the image in a different format and save your image as boat_scene.jpg

JPEG doesn’t support Layers or the Transparency that is in some of the layers, so the Save As dialogue will ask you to Flatten the image

and finally it will ask you to specify the Quality for the JPEG. The more compression the smaller the file, but the worse the quality. I set mine to 90%.

That’s it, you can upload your image to your blog or to the forums and show it off.

…that’s nice dear, I’ll put it on the fridge.

References

Hamilton, G. (2007). An Introduction to GIMP. [Online] Available at: http://people.clarkson.edu/~hamiltgr/gimp/gimpDoc.html [Accessed: 14 November 2010]

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5 Responses to Introduction to the GIMP

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