Interview with Øyvind Kolås, GIMP developer (2017)

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GIMP is Free and Libre Open Source Software, but none of it is possible without
the people who create with and contribute to it. Our project maintainer Jehan wanted to interview the volunteers
who make GIMP what it is, and share their stories so you can learn more about the awesome people behind GIMP!

Early interviews with co-maintainer Michael Natterer
and Michael Schumacher were
published shortly after the first Wilber Week. Unfortunately,
the rest of the interviews from that event have never seen the light of day - until now!

Our previously resurfaced interview was with Simon Budig.
The interview in this article is about Øyvind Kolås. He is the maintainer of GEGL and
babl, the color engines of GIMP. His work was instrumental in (among many other things) the
long-waited non-destructive filters implemented in GIMP 3.0!

This interview took place on February 4th, 2017. In addition to Jehan and Øyvind, Michael Schumacher, Simon Budig, and Debarshi Ray were also involved and asked questions.

[Øyvind Kolås, by Michael Schumacher, CC-BY-SA - 2019]

Øyvind Kolås, by Michael Schumacher, CC-BY-SA - 2019

Jehan: Okay, hello Pippin! So, first off, how should we call you, Pippin or Øyvind?

Øyvind: If people know how to pronounce ‘Øyvind’, that is perhaps easiest. In some contexts it is a difficult name to pronounce and I have to go by my nickname Pippin.

Jehan: Ah, and where does it come from?

Øyvind: The nickname Pippin originates from Lord of the Rings. The first time I went on IRC, must have been ‘95 or ‘96, I had to come up with a nickname for myself, and I chose the nickname of a hobbit. I used the nickname “Sméagol”.

Jehan: But you’re not very small.

Øyvind: No, but Sméagol is the hobbit in terms of Gollum, and I kind of decided that I didn’t want to have the association that came along with that hobbit. So after just one day of using that nickname I skimmed a little bit through the history of the Lord of the Rings again, and noticed that the “Pippin” hobbit might be more appropriate. He’s a hobbit that’s a little bit too curious – he throws stones in Morannon and stares into Saruman’s palantír and wonders how things work.

Jehan: So, how many times have you read Lord of the Rings?

Øyvind: Two or three times? I’ve seen the movies more than once.

Jehan: How are the movies?

Øyvind: They’re okay. They’re long!

Jehan: So, you’re the GEGL maintainer.
Maybe first, let’s explain what GEGL is. For people who read the website, they may know GIMP, maybe not necessarily GEGL.

Øyvind: GEGL is a library or system where you can plug components together. You can create chains of image manipulation filters or operations. So you can first adjust the colors of an image, and then apply some sharpening to it. So you can construct those as a flow chart or similar – “First do this then do that, then do that” – so programmers can create data structures representing such chains or flows of image data, and developers can use such components to use in the chain.

Jehan: And so how did you come into this project?

Øyvind: I had been using GIMP for quite a while, and then at some point I was experimenting with writing my own video editor. And I started implementing various transform tools and operations – I implemented perspective rotation tools and similar. And while I was doing that, I was also taking a look at how GIMP was doing some such transformation tools and operations. And I realized that the perspective transform in GIMP produced not quite the results that I would like it to produce.

It had big problems with moire and aliasing when you did severe perspective transforms, for instance. So with my newly gained knowledge of making something similar myself, I sat down and tried to figure out how to improve what GIMP was doing. So I made a patch fix to add adaptive subdivision super-sampling to the transform tools.

Jehan: So it was not GEGL?

Øyvind: It was for GIMP. That’s how I got involved in the GIMP project, it was my first patch that I did there. But even that was after I had ran into many of the people from the GIMP project at a GNOME conference in Copenhagen in, I believe, 2001.

Jehan: Okay. So, how does GEGL change GIMP? What is GEGL for GIMP?

Øyvind: Well, I’m the wrong person to ask that question. I know how GEGL works. I know many of the needs of GIMP. But the person who has the greatest knowledge and detail of how GEGL makes that work and happen for GIMP is
Mitch.

Jehan: We should have asked him yesterday then!
Thank you. So, maybe you can still explain some of the cool features in GIMP. Like what everyone has been talking about, such as non-destructive editing, which is enabled by GEGL?

Øyvind: So this graph-based data-flow chains of operations that you can do with GEGL – most parts of GIMP have been transformed to make use of that. The core thing that is currently non-destructive editing in GIMP is the layers dialog. Other software has more capabilities there, but it’s not easy for us to know what interface to provide and present to the user to add such capabilities as drop shadows, or blurs, or color adjustments.

Jehan: It’s easy or not easy?

Øyvind: It’s easy to do it as a hack or as a proof of concept, but it’s more difficult to figure out how to do it in a way we can guarantee will be stable for many years into the future. So where we are currently, as we are close to being able to release GIMP 2.10 is that we’re doing all the layer processing that GIMP 2.8 use to do, but there’s no hacks – we’re using GEGL as the engine instead.

Jehan: So, do you use GIMP a lot?

Øyvind: Sometimes GIMP is the appropriate tool, and sometimes there’s other existing software that I use as a tool. And sometimes the tools I want or need don’t exist, and then I try to make those tools.

Jehan: You also have a background as an artist. Could you maybe speak on this?

Øyvind: From when I was a teenager, I’ve been doing both visual arts such as painting and drawing, and being interested in creating media in various forms such as videos. The only form of creative expression that I haven’t much played with is music. My original education and training was in fine arts. Only after having done that for a few years did I go back to computers and digital media, and go more the academic route in computer science.

Jehan: So you studied computer science before, then you went to art?

Øyvind: No, but I’ve been doing computer graphics since I was 14 or 15 years old. I was inspired by the demoscene community and having access to dial-up bulletin boards systems with people discussing programming techniques and languages. They contained tutorials in C and Pascal and Assembly and also involving Turbo Pascal. Demoscene-style graphics are things I’ve done since before University level age, along with experimenting with painting and traditional physical drawing media.

[Illusion, CC-BY-2.0 - 2019]

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