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Getting professional results from Gimp

Jack Wallen Tech Republic

Published: 16 Jul 2007 16:18 BST

Image editing and creation is not limited to the Mac or Windows. In fact, one of the flagship applications for Linux (and open source) happens to be a photo manipulation application. Gimp is a very powerful tool that equals (and, in some instances, bests) its proprietary competition.

Unfortunately, one of the stumbling blocks to adopting Gimp (GNU Image Manipulation Program) is usage. Its unique user interface is not like Photoshop. However, it's also easy to learn and can handle many advanced features. This article will show you how to use Gimp and discuss some of its advanced features.

Installation
Installing Gimp in Linux shouldn't be an issue. Every Linux distribution comes with Gimp. The few exceptions to this rule would be some of the smaller live CDs (ie, Puppy Linux). If you are running a distribution that doesn't have Gimp installed by default, you can run something close to:

yum install gimp

The installation system will take care of the dependencies.

Running Gimp
Gimp does not demand the resources of most graphics manipulation programs. Checking the top listing for Gimp, you'll see the screen shown in figure A.

Figure A: You'll never see Photoshop using fewer resources

Gimp's usage is on the third line of the listing. As you can see, top shows that Gimp is only using 36MB of RAM, 2.7% of the CPU, and 5.3% of the total RAM.

Once Gimp is up and running, you'll notice two main (and separate) windows. Take a look at figure B, which shows the three main working windows for Gimp. The main toolbox is the main window for the application. The layer dialog window (as labelled below) houses the dialogs for layers, channels, paths, brushes, patterns, and gradients. As any graphic artist will tell you, you can't succeed without knowing and using layers.

Figure B: Get used to the multi-window view; it's Gimp's way of life

There are tricks to getting used to Gimp's layout. First and foremost are menus. Although you see menus attributed to each window in Figure B, some share similar entries. What you don't see is the right-click menu. One of the issues hard-core users complain about is efficiency. Having to constantly move from one window to the next is a waste of time. With that in mind, Gimp developers made it easy. Right-click in the image window to see a new menu appear, as seen in figure C.

Figure C: The right-click menu will become the most-used menu in your Gimp

From the right-click menu, you can access nearly every tool available to Gimp. This will save you time and effort.

Now that we have basics of the interface out of the way, let's start getting to work.

Layers
Layers make working with images much easier. Without them, working with an image would become an exercise in tedium and insanity. Layering can be seen like a transparency: on the base layer, you have a background image, but you can layer a separate image without affecting the background. Let's use an example. First we will deconstruct the image from figure B in order to strip away a layer, combine layers, and add it to a layer of another image.

In figure D, we will delete the background layer from the working image window. As you can see, we have highlighted the background layer and will press the delete button.

Figure D: If you hover your mouse over the dustbin icon, the delete-layer tool tip will appear

Once the layer is deleted, the image in the image window will appear differently. Figure E gives an example of this.

Figure E: With the background layer deleted, the image has a transparent background

Remember, your goal is to copy this image onto another. If you were to copy the image as is, you would only copy the active layer. In figure E, there are three layers: drop-shadow, Jack, and grow-me. Whichever layer is highlighted at the time of copying will be the layer copied to the clipboard.

In order to copy all three layers at once, the layers must be merged. Layers can be merged in two ways. Firstly, you can merge layers down. For example, let's say you only want to combine layers one and two. To do this, you would first highlight the top layer you want to merge down. So, if you wanted to merge layer one with layer two, highlight layer one. If you wanted to merge layer two with layer three, highlight layer two. Next, open the layer menu and select merge down. You will then notice only two available layers in the layer descriptions, as seen in figure F.

Figure F: The only remaining layers are Jack and grow-me

The problem with merge down is that you still have two layers to copy. Should you want to copy the entire image, you will have to merge the layers via merge visible layers. To do this, either press Ctrl+M or go to the image menu and select merge visible layers. Either way, you will get a dialogue box of options: expand as necessary, clipped to image, or clipped to bottom layer. We mostly stick with the default (expand as necessary). Once you press OK, you will notice only one remaining layer in the layer descriptions window (in our case, grow-me).

Next, copy the merged layers onto another image. If you were to copy the merged layers onto an image without creating a new layer, any manipulation you try to do to the copied image will affect the base layer itself. Adding a new layer allows you to play with various aspects of the copied image without affecting the original background. Take the new image and add a new transparent layer on top of it, as seen in figure G.

Figure G: A face just asking for a name

Once you click on the new layer, you will have to decide the name, size, and fill type of the layer. It's best to get in the habit of giving layers descriptive names. When you're dealing with an image with many layers, it can get rather confusing. Since you need to keep the transparent nature of the copied image, select transparency for the type. The size will fit the base image, so there's no need to modify. Press OK and you will notice no change in the image window. You will, however, see a new layer appear in the layer description window for the new image.

Go back to the merged layer image. To copy this, press Ctrl+C. Now go to the new base image. Make sure the new layer is highlighted and press Ctrl+V. The new layer is pasted on top of the base layer, as seen in figure H.

Figure H: The pasted layer is much too dark

Obviously, you can't use the layer as it is. We intentionally copied a dark image onto a dark background so we can show you a little about layer manipulation.

Take another look at figure H. The floating layer is the layer you just copied but have not anchored down.

You need to adjust the opacity of the floating layer so that it doesn't just look like mud overlaying the base layer. Drag the opacity slider to the left. You'll notice the floating layer growing more and more transparent. We are going to drag the slider to the 30.2 position and then anchor the layer. As you can see in figure I, the image is not nearly as muddy as it would have been without the layer manipulation.

Figure I: You can now see the added layer isn't too dark

It's not perfect, but it illustrates a good point: layer manipulation is critical to good graphic design with Gimp.

QuickMask
The QuickMask tool is one of those tools that, once you get the hang of it, you'll use more often than not. QuickMask allows you to fine-tune only selections of an image. To use QuickMask, simply click on the QuickMask button on the bottom left of the image window, as seen in figure J.

Figure J: QuickMask helps fine-tune images

When you click the QuickMask button, the entire image will appear to have a translucent red layer over it. Figure K illustrates this.

Figure K: The red glow means you're ready to begin using QuickMask

Press the QuickMask button again to return it to normal mode. We're going to use QuickMask to give the picture a unique look. Press the QuickMask button and then press the eraser tool. Make sure you're erasing with the colour black, otherwise QuickMask won't work. So, using the eraser with the circle fuzzy (13) brush, we are going to "erase" the face from the picture. We'll use the circle fuzzy brush so the edges aren't sharp.

Once we erase the face from the picture, we have a clown-white look, as shown in Figure L.

Figure L: Circus clown? Surely not

If you click the QuickMask button again, you will see the area erased with a dotted line around it. This means the area has been selected to be manipulated. Make sure the layer you are working on is the background layer. While the face is still selected, right-click the image and go to filters, distort, whirl and pinch. Press OK; when the filter is processed, your image is ready. Figure M shows the changes.

Figure M: Making yourself look creepy is simple with QuickMask

Logos
Another really great Gimp tool is under the xtns menu in the main toolbox window. Select that menu and go to script-fu, and logos. From the logos sub-menu, there are a number of styles to choose from. Each has its own unique characteristics. Let's take a look at the glossy logo. Select glossy from the list and a new window will appear, as seen in figure N.

Figure N: There are a ton of options in the script-fu log window

The most important options you'll want to configure are:

Text: this is the actual text that will appear in the logo.
Font size: actual font size.
Font: the font used.
Blend gradients: these will be the colour schemes of the logo.

There are quite a few more options to explore, but this list will get you going right away. Once you enter your text, select the font and font size, and select your gradients, then press OK to create the logo. As an example, we chose "Jack" as the text, 100 as the font size, and aneurism as both blend gradients — if you choose different gradients for text and blend, the end result will not be clean. Figure O illustrates the end result of the logo.

Figure O: With the help of script-fu, anyone can create elegant, professional logos

Final thoughts
Gimp is an incredible image-manipulation package. Although this article only scratches the surface of the power and ability of Gimp, you can see from these examples how well this application easily meets the needs of graphic artists on every level.