Gimp-Tutorial Part 1
Gimp is a complete program to edit graphics. Too bad that the menu handling is very complicated and at the beginning, everyone has problems navigating through the numerous and deep menus; even experienced users have some difficulty. In this tutorial we review a practical example and learn how Gimp works.|
In this tutorial, we will create an animated banner. First, we need a frame with the standard sizes: 468x60 pixels. Select the menu File->New and generate a new clean frame. The "Image Type" would have to be RGB if you wanted to create a colored picture. The "Fill Type" should be transparent. After pressing OK Gimp opens a new window with the chosen width and height. The chess pattern shows that the picture is transparent. |
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Next, you should open the layer menu. With the right mouse button you click on the new picture and then choose the menu Layers->Layers & Channels. An important part of any work with Gimp belongs to the so called Layers. You will imagine what layers are if you take a few transparencies. If you wanted to change the picture a little bit you could change it on a new slide. Without any damage to your main image, you could just remove the change if you deleted this slide and the remaining part of the picture would be untouched. But layers offer many more functions. You can comfortably work with diffuse (semi-transparent) objects which take are an important part in animated GIF pictures.
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A picture of Tux belongs on every good Linux banner. If you did not have a Tux picture, you could copy the one displayed on the right side (penguin.gif).
Then, you open this picture using Gimp (menu File->Open).
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After Gimp opened the window with the penguin first. You should transfer the picture into the RGB format. The maximum number of colors in GIF pictures is 256 and this is not enough for our presentation.
The GIF picture format (also called indexed-format) does not support semi-transparent handling and a few tools cannot be used with GIF pictures. That's why you should transform GIF into RGB. Before you save your picture in the GIF format, you have to re-transform it into the indexed format. OK, then. You click with the right mouse button on the penguin and choose the menu Image->RGB. The background of the penguin picture is still white, but we want to change it to transparent. Then it will not cover the other pictures later. First you have to add to the picture the so called "Alpha-Channel". Choose Layers->Add Alpha Channel. The picture gets a new transparent layer. If you deleted parts of the picture you would "see" the transparent layer behind. Next you try to delete the white background. This can be done on different ways. A very powerful tool is the option "Select by color" which selects all parts of the picture with a selected color. Your problem is that the belly and the eyes of the penguin are white, too, and we would select them together with the background. Just take another tool: the "Fuzzy selection", available in the Gimp main window (see right). Click on the button twice to get the extra window with additional options
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In the opened option window, you deselect all options. Antialising avoids a sharp cut at the border of the penguin but produces a soft float between the penguin and the transparent background. You would get a thin white surrounding which could be useful for other things, but not now.
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Now you select the background of the penguin. It appears a flashing black-white line everywhere where the border of the selected part is. The menu Edit->Cut cuts this selected part. The parts left, right and between the feet are not connected to each other so you have to cut all five parts separately. After cutting the white background, the parts should be replaced by the dark grey chess pattern.
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Then you have to fit the sizes of the penguin to the banner. Use the menu Image->Scale. Then you enter a height of 150 pixels instead of the actual 257 pixels. The button "Constant Ratio" takes care that the width is changed properly, too. After checking OK the picture becomes smaller and is nearly twice as high as the banner. With the menu Select->All you select the whole picture and a Edit->Copy puts the picture into the buffer. On the banner you select Edit->Paste to get the picture out of the buffer. Now you should see the penguin in the banner frame. But it does not have the right position.Before you change this have a look at the layer window. There an additional entry appeared with the description "Floating Selection". To put the penguin on its own layer select at left-down in the "Layer & Channel" window the empty sheet of paper. Now the penguin is placed on its own layer and can be edited separately from the rest of the picture. Next you move the penguin a little bit so that you see its head much better. Choose "Move Tool" (see right). With this tool click on the penguin and move it so far that the head can be seen at the bottom of the banner.
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But the head is still too big. You change this using the "Transform Tool"  . A double click on it opens a window with additional functions (if the last option window has been opened since the "Fuzzy selection" it would show the new options now). Choose the option Scaling and click on the penguin in the banner. You could make the penguin smaller if you changed its size with a pressed mouse button. If you pressed the keys Ctrl and Shift while moving the mouse Gimp would take care of the constant ratio of height to width. After making it smaller, you can move the penguin with the "Move Tool" to the position where you want it to be.
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The penguin is too cute to let him be alone on the banner. You can copy Tux by clicking on it with the right mouse button and choosing "Edit->Copy" and "Edit->Paste". Now a new "Floating selection" appears in the "Layers & Channels" window. A click on the empty sheet of paper sets the second penguin on its own layer. Then you move the second one a little bit to the side because it is overlapping the first one. (Use "Move Tools"). This procedure can be repeated until we have five penguins in total. Every penguin gets its own layer
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Finally, you can name each layer so you will be able to separate them a little bit better. A double click on one entry in the "Layers & Channels" windows opens a small window where you can rename the layers. How about layers with the name "Tux1" to "Tux5"? A click on the "eye" at the left of one entry would set if this layer was shown or not. This is a very good tool for complex pictures with many objects.
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Now the picture should look like:
To get this, you have to rotate them more or less. |
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Also for this change, use the "Transform Tool"
. In the window with the additional options, you find the choice "Rotation". Now you can select the different layers and rotate the corresponding penguin pressing the mouse button. After rotating all penguins, they have to be moved so that just the heads can be seen.
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To avoid any frustration, you should save the file from time to time. Click with the right mouse button on the banner window and choose the menu File->Save As. Then select a proper directory where you want the picture to be saved. Choose a file name like "penguinbanner" but without any extension like .gif or .jpg. You have to remember that we use the RGB mode that does not support the GIF format. JPEG does not support any layers or transparency; also you lose information due to compression. The best would be if you choose the format "gzip" which is found at the end of the list; "gzip" is the Gimp specific format XCF that is already compressed with gzip to save space (XCF is huge). This format saves the picture as it is with all layers like transparency and any other fancy work. As you can see, Gimp automatically adds the correct suffix to the end of the file name and your picture is called "penguinbanner.xcf.gz". |
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