Gimp Tips Part 2: Rounding Corners
By Jason Jones
Two methods exist to create a rounded corner in Gimp 2 and they both have their strong points in certain situations.
In order to illustrate my point, take the selection below, for example.
To round this out, I’d definitely use the Round Script-Fu option.
rounding using script-fu -> selection -> round
This script works on very simple selections, like the one seen above. In order to use it, right-click on the image and follow the menus to Script-Fu -> Selection -> Round
Then choose the radius with which you’d like to round. 0.1 or 0.2 usually suits my needs just fine.
After you make your selection you’ll notice the effects right away.
You’ll have perfectly rounded corners for everyone to admire.
So…. What if you have some crazy selection you need to round? Will this method work? Let’s see….
I created a monstrosity of a selection with many corners which need rounding.
Then I applied the script to it…
Definitely not what I wanted… So there must be another option, right? What are you kidding? Are we using Linux, or aren’t we? Of course there’s another option.
shrink / grow method of rounding
I’m not quite sure if the creators of Gimp intended what I’m about to show you, but it works fantastically – so I hope they never remove the functionality.
With the above image at hand, to round the corners, simply right click and follow the menus to Select -> Shrink
Here, you’ll probably have to fiddle with your settings for each individual selection you wish to round. The rule is: The more you shrink, the more you round.
*note*Be careful not to destroy your image by shrinking too much. If you shrink too much, things will start to disappear in your selection.
I chose to shrink mine 15 pixels.
After you shrink the image, the next step is to enlarge it again by right-clicking and following to Select -> Grow
Here, it’s important you select a number which is between 0 and the number you shrank it. The closer the grow number is to the shrink number, the less the inner corners will be rounded. e.g. If I set my grow number to 15, my inner corners will not be rounded at all.
So, I chose 10.
After hitting “Ok”, if you chose your settings correctly, you’ll notice a wonderfully rounded selection.
Now… If you’re going to fill your image in, you’ll most likely want an anti-aliasing effect on the border of your selection. This gives the fill a nice soft feel around the edges.
To accomplish this, you’ll want to feather your selection.
In order to do this, you right-click on your image, and follow the menus to Select -> Feather…
You’ll not want to put a number too high in the resulting box, however… If it’s too high, when you fill your image in, the corners will seem more like a gradient, than an anti-alias.
2 pixels suits me most of the time.
Click OK and your selection is ready to be filled. I filled mine with a simple black paint from the paint bucket.
If we zoom into the corners, we’ll see the feathering at work…
Notice the gray line right inside the selection? That’s the feathering that gives your fill a nice soft edge; otherwise, it would fill to the selection and stop, leaving a very harsh edge everywhere.
What you’re left with are very nice, rounded corners in your image! Happy Gimping!