By default, GIMP offers about 60 patterns you can choose from. It is not enough for an art-minded GIMP user. The GIMP compatibility with Photoshop files, including ABR file, allows you to install a Photoshop pattern in GIMP since finding a PAT file (the native GIMP pattern file format) is not easy. If you prefer to create a custom GIMP pattern yourself, that’s great.
In general, there are two ways to create a GIMP pattern. First, you can create from scratch by taking advantage of the tools offered by GIMP. Second, you can take an area of image (by cropping it) you think it’s great to be turned into a pattern.
A pattern itself is technically a small background image. When you apply a pattern on a certain image area, this small image is copied repeatedly to fill the selected area. Thus, there is one key rule you need to know before creating a new pattern. The image dimension you will use as the pattern should be in a square shape (i.e. 500×500).
How to create a new GIMP pattern
Before creating a new GIMP pattern, make sure that you have administrator access on your computer (or root in Linux). It is because of you will add a new file to the patterns folder under the GIMP installation folder.
If you use Windows, you can run GIMP as administrator by right-clicking GIMP on the start menu and select More -> Run as administrator.
If you use Linux, you can type
sudo gimp on the terminal to run GIMP as root.
Once GIMP is open, create a new file by going to File -> New (Ctrl+N). Again, make sure to use a square image on your pattern. To create a square image, use the same values on the height and the width then you can click the OK button to start creating your pattern.
If you have a drawing skill, you can use the GIMP tools to create the pattern. If you don’t, you can simply take an image area you think it’s great to be used as a pattern and add it to the pattern you are working on.
Once you are done creating the pattern, go to File -> Export As (Shift+Ctrl+E). On the appearing dialog box, set the file type to GIMP pattern (pat). Give your pattern a name and set the destination folder. If you use Windows, you can set the destination to
C:\Program Files\GIMP 2\share\gimp\2.0\patterns\. If you use Linux, you can set the folder destination to
/usr/share/gimp/GIMP version/patterns. Click the Export button.
Now please try to use Bucket Fill Tool and set the Fill Type to pattern and check if the pattern you have just created has been available. If you can find it, try to restart your GIMP.