Sometimes it's all about design.
While I was creating a new website, I needed to center the background image in a way that it matches the centered text. But how do you find the exact center of an image?
GIMP can help you find the exact center by using a Guide. This can be best described as a "helper line" at the position you want it to be. By using percentage values, the exact center can be determined.
With the image opened, click on [Image] in the menu, then hover over [Guides] and finally click on [New Guide (by Percent)].
A popped up menu asks whether the guide should be based horizontally or vertically. For now use horizontal and set the position to 50.00 (= 50%).
This creates a blue horizontal helper line in the center of the image:
Now we just need another helper line, vertically this time, to show the exact center. Once again create a new guide by percent, but this time use "Vertical" direction. Set the position to 50%:
Now with these two lines in place, the exact center of the image is showing at the line crossing.
You can now resize the canvas size ([Image] -> [Canvas Size]) to adjust the image so it will be shown in the exact center.
In case you're wondering what this image is for, it is for the website of Neuklang.ch, which offers relaxation using Tibetan singing bowls in eastern Switzerland.
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