HowTo: Create Artistic Backgrounds using the Gimp -- Part 2
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Posted: 2 Dec 2004
|Learning to use Linux at Home and Work
Welcome to my ongoing series of HowTo articles designed to help Linux newbies get comfortable with Linux. Before trying any of these HowTos, take a few minutes to study the prerequisites so you can hit the ground running.
This HowTo is about using the Gimp to manipulate pictures to create an original that can be used as desktop backgrounds. You will use simple methods for selection tools, layers, copy and paste, changing the size and transparency of floating layers, and anchoring. The Gimp can do a lot more than is described in this simple HowTo, but here you will learn some of the basic and simple ways of doing things.
In Part 1 we created a picture and pasted one graphic. We also learned how to select an odd shape. I want you to repeat this procedure so we can create a new picture from the selection shape. Make the selection as instructed in Part 1.
Click Edit > Copy > Edit > Paste as New. You will get this new picture.
Notice the chequerboard pattern. This is to let you know that this part is transparent. We shall use layers to impose the shape onto the picture we want to paste. The professionals use masks for this, but layers are something we should learn how to use at this stage, and you can do all sorts of other useful things with them.
Make sure the new picture is the one shown in the Layers dialog, by minimising the rotzoomer picture and clicking in this new picture. In the Layers dialog there is an icon for creating a new layer.
If you hold the mouse over it, a tool tip will tell you to press the Shift key while clicking it to see the New Layer dialog. Do this and you will see this pop up.
The Transparent radio button is highlighted, which is the default if we just click the new layer icon. Change this to White and click OK.
A new white layer will appear in the dialog, and your picture will change to white with your selection shape in it.
What we need is the white picture on the bottom. In the Layer dialog, this is highlighted with a blue bar. Use the lower layer icon, which is the down arrow shape at the bottom of the pop up, to move it to the bottom.
Now in the picture window, you can see your shaped picture on top of the white background.
Right click the white layer in the Layers dialog and click on Merge visible layers. Click OK.
The two layers will become one, thus:
Click Select > None. Click Select > By Colour and click on the white area in the picture window. Click Select > Invert. Click Edit > Cut and you are left with a white shape with a transparent cutout the shape of the original selection from the rotzoomer picture.
Now we have to create a new transparent empty layer. Do you remember how?
Click the new layer icon in the Layer dialog. Yes, of course I remember!
We leave this picture alone for a while by minimising it and prepare our picture to be pasted. If you want it to look a bit different you can click Filter > Whirl and Pinch or something else to change it. I did that. You can also use Tools > Transform tools and use Shear or Perspective to change the shape and view. When you are happy with the result, use Image > Scale to get it to near the right size for the cutout. Don't forget to check that both picture and cutout have the same zoom factor in their respective blue top bars.
In your newly modified picture, which will be pasted, click Select > None and Select > All, click Edit > Copy and minimise this picture.
Now we return to the cutout. Raise it by right clicking its image in the Images pop up. Make sure the empty layer is selected in the Layers dialog with the blue bar. In the cutout picture window, click Edit > Paste. Your picture will look something like this:
You can see that the whole picture is not shown as it is wider and shorter than the actual layer.
We modify this with our trusty Transform Scale tool. Click Tools > Transform Tools >Scale and click on the picture. The grid with the corner square will overlay the picture.
Move the corner boxes so that they make the picture fit the underlying layer.
You can see in the Layer dialog that this is a floating layer (it has not been anchored yet).
Click Layers > Anchor Layer. The Layers dialog will look like this:
We are going to repeat the merge of the two layers, but first we make sure they are in the right order to let the white cutout show up on top. Lower the top layer with the down arrow icon.
Right click on the lower layer and click Merge Visible Layers.
In the picture window, click Select By Colour and click on the white background. We are going to cut this away leaving a shape that will fit right into our rotzoomer selection shape. Click Edit > Cut.
You may have problems using select by colour if your picture has areas of white. You can colour the white layer before you merge with a plain colour not in your picture palette to avoid this problem.
Click on Select > None if it is there to make sure we can select everything we want. Click Select > All, Edit > Copy. Minimise this picture in case you want to go back and change things for another Edit > Copy.
Click on the rotzoomer picture and click Edit >Paste > into. Our created picture should fit perfectly into the selection.
The last but one task is to change the transparency of the picture shape. In the Layers dialog move the transparency bar to about 40% as shown.
Change the amount to suit your two layers to get the best result.
When you are happy with the result, click Layer > Anchor Layer and File > Save As rotzoom2.png.
This is my end result. I'm sure you can do much better.
In Filters > Map there is a tool called Fractal Trace which you can use on your picture. Don't forget you can make a selection in a picture to be pasted, and invoke a filter or script-fu on this smaller area to make some quite amazing modern art.
If you use KDE you can put a selection of your backgrounds into a folder and use the Control Panel Background icon to select multiple backgrounds and change them every 10 minutes or so to display your own art show, or you can use the xscreensaver slide show to do the same sort of thing.
Don't forget to sign your best work before you share them with your friends.
Next Up: In Part 3 we are going to change some of the background using selections and filters.
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