Creating Color Contrast Images in The Gimp
Novell Cool Solutions: Tip
By John O'Riordan
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Posted: 25 Jan 2007
The Gimp comes with each installation of Opensuse. It is a fairly powerful graphical tool but most people don't really spend the time to learn how to use it as all the available options can be quite daunting. In the few steps below I will show you how to create black and white images with just a few colour components for striking images.
For example we will turn this........
So lets start....
1) Open your image in The Gimp and save it as a .xcf file.
2) Ensure the extension of the file on the top of the image changes to .xcf.
5) Then select Edit -> Paste as New
9) Next copy your clack and white image by pressing Ctrl+A (to select all) and Ctrl+C (to copy).
10) Select the colour picture and go to Layer -> New Layer.
13) In the layers box click on the anchor button. (You should see the floating image and the B&W layer merge).
15) So now we have two layers. Each layer is like a pane of glass with the picture painted on it, siting on top of each other. You can hide or show each pane by clicking on the eye in the Layer box. Try clicking the eye beside the B&W pane. You will see the colout image underneath once again.
16) Next highlight the colour image in the layers pane.
17) In the image window select Layer -> Transparency -> Add Alpha Channel. This will allow you to remove parts of the picture on the pane to expose the pane beneath. This is how we will achieve our final image. So first we need to place the colour pane on top.
19) Next select the eye next to the B&W layer to hide it from view. As it is currently underneath the colour image you should notice no change.
20) Next select the eraser tool from the main Gimp Window. Now you can start erasing* the parts of the image you want to appear in black and white.
21) As you erase parts of the image you should see little grey boxes which represent transparency. Once you have erased the parts of the image you want to appear in Black and White again select the eye beside the B&W layer and you should see the effect.
Note on erasing: When erasing you can also cut parts of the image out using Ctrl-X. You can select large chunks using the rectangle tool, select irregular regions using the magic wand tool. Or you can zoom in and use the eraser tool to remove small parts you want removed.
The magic wand tool is very useful in that it selects similar regions. Be careful though as it doesn't always select what you think it will. Play around with it and you'll soon figure it out. The best tip would be to hold down shift and left click to pick a region. Keep the key and mouse button pressed and move left or right across the screen to select less or more of that region. Once you have selected the region you want you can cut it out.
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