Open Source

DIY: Advanced GIMP techniques and tools

A Photoshop alternative that won't cost you a dime is the GNU Image Manipulation Program, better known as GIMP. Get several tips on using the open source graphics editor.

When companies are operating on a very tight budget, graphics tend to fall to the wayside. Unfortunately, many users still don't know about the GNU Image Manipulation Program (GIMP), an open source and free alternative to Photoshop. With GIMP, employees can get creative and build a library of images for the business. Here's a demonstration of a couple of GIMP's advanced techniques and tools.

Layer Masks

One of the most powerful GIMP techniques you'll use is Layer Masks. A Layer Mask allows you to effectively combine layers together, making them only interact only in ways you like. I'll first show the end result, and then we'll work our way back to it.

In Figure A, you see that we're striving for glowing purple eyes on a black and white photo. Figure A

Remember: This is the end result.

If you try to pull off the effect in Figure A without Layer Masking, you will fail because when you desaturate the colors on a layer, all colors on that layer are changed to shades of black and white. You need to use Layer Masking to accomplish this task.

Here are the steps to recreate what I've done. First, the layer must be duplicated, and then the top layer gets the desaturation.

  1. Open the original image.
  2. In the Layers And Channel window, right-click the image and select Duplicate Layer (Figure B).
  3. Select the top layer in the Layers And Channels window.
  4. In the main window, right-click the image, go to Colors | Desaturate, and then click OK.

Figure B

You will not have the Layer Mask shown in this image yet. We'll create that soon.

The next step is to go to the bottom layer and create the glowing eyes by selecting a color, selecting the brush you want to use, and drawing in the color for the eyes. Now it's time to create the Layer Mask by going to the Layers And Channels window, right-clicking the top layer, and selecting Add Layer Mask.

In the resulting window you have seven choices. The Layer Mask type you want is White (Full Opacity), which means everything will show on the Layer Mask except what we erase. What is erased will allow what is in the bottom layer to peek through. To make this happen once you create the glowing eyes, follow these steps:

  1. Click the top layer from the Layers And Channels window.
  2. In the main window, select the Erasure tool. It's very important that you make sure the color white is in the foreground.
  3. Using the Erasure tool, erase the image of the eyes to reveal the glowing eyes beneath.
  4. Once you have it exactly as you want it, right-click the top layer in the Layers And Channels window and select Apply Layer Mask. Your glowing-eyed image is ready to save. I highly recommend you save the image as you work in the GIMP's native .xcf format so you can retain all attributes of layers. When you finish with the image, you can save it in whatever format you like.

The Perspective tool

Let's add some text to that image using the Perspective tool, which allows you to create an object and then change the perspective of the object, giving it somewhat of a 3D feel. Here's how to add text to our sample image:

  1. Add a new layer to the image by clicking the "+" button in the Layer tab of the Layers And Channels window.
  2. Select the Text Tool and then configure your Font, Size, and Font color.
  3. Type the text you want to add into the layer.
  4. Select the Perspective tool (Figure C).
  5. Using the handles around the text, click and drag until you have the perspective exactly where you want it.
  6. Click the Transform button in the new window that appears.

Figure C

Once you click the Perspective tool, the options in the lower portion of the window will change, allowing you to configure how the perspective is handled.
Figure D shows the newly added text with the perspective changed. Figure D

The text jumps out at you and better follows the design of the image.

Shear the text

Let's take this one step further and adjust the shear of the text. The shear allows you to change the tilt of an element, effectively shifting a section of an image one way and another in the opposite way. To do this, select the text layer and then select the Shear tool (it's to the left of the Perspective tool). Now, go to the text box, click the bottom left or right corner, and drag the box either to the left or the right (Figure E). Figure E

Until you click the Shear button in the Shear window, you can continue to manipulate the text box.
When you complete your shearing, click the Shear button to apply the changes. Figure F illustrates the effect of the Shearing applied. Figure F

The text now looks even more dimensional.

Summary

Thanks to these advanced tools, you now have the means to really make your graphics stand out. When we cover GIMP in future DIY posts, we'll illustrate more great techniques and tools. Until them, happy "gimping!"

About

Jack Wallen is an award-winning writer for TechRepublic and Linux.com. He’s an avid promoter of open source and the voice of The Android Expert. For more news about Jack Wallen, visit his website getjackd.net.

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