Safe as Milk

Color management in the GIMP

With the recent GIMP 2.3.3 release, color management in the GIMP is now well past what we have had before. Recently, someone asked me what color management is, in simple terms, so I wrote the following. There might be some error in here, unfortunately I don’t always have the time to research what I write. Corrections welcome.

Color is one of the most subjective things around – what are “red”, “green”, and “blue” quantitavely? Every input device has a slightly different perception of color – try scanning a photo with 2 different scanners, or taking a photo of the same scene with 2 different cameras. The results will be almost, but not quite, the same.

There are similar problems for output – two screens will show the same data with slightly different colors, and the same image printed to 2 different printers may be different.

Usually, the differences are small enough that we don’t really care (although if you do the test, you might be surprised at how big the difference is). But for print work and graphics design, color is everything. We want to start from a photograph, have colors from the photo appear exactly the same on the screen, and then after airbrushing away those freckles and printing the photo, we want the colors to look the same as the original.

Company logos and art-work are chosen with their colors by meticulous people who couldn’t tolerate a slightly different shade of pink being in the logo than the one they chose – imagine a graphics designer ripping his hair out while passing a billboard add saying “No, no, they ruined my work.” because the charcoal grey he had chosen was slightly darker than the printed result.

So to address all these issues, an international standards body was established, to decide what color is. In fact, there are two groups – the first, the CIE (Commission Internationale de l’Eclairage) defined the standard for colorspaces, and the ICC (International Color Consortium) defined a standard way to convert between these standard colorspaces and device-specific colorspaces. The CIE colorspaces are XYZ for linear additive color (plates in a printer, or diodes on a screen, for example) and La*b* for “perceptive” color – which doesn’t quite work the same way. So a value in one of these colorspaces is the same, everywhere.

They also defined a means of converting from these standards to other colorspaces. Our typical RGB colorspace represents the way light waves combine to create color. CMYK, for cyan, magenta, yellow, blacK, is the way that paints mix to generate colors (since paints absorb rather than reflect colors, this is called a subtractive colorspace – as you know if you’ve ever painted, when you add more & more paint to a mix, the color gets darker & darker, until every addition just gives a murky brown).

The means to changing between colorspaces is a color profile (also called an ICC profile). These can be embedded in images to say what colorspace was used to capture the data, to allow it to be converted to XYZ, and from there to another colorspace.

High-end scanners and digital cameras embed these profiles in the images that come from them. Screens and printers have profiles associated with them too. So we can load an image, and by applying the embedded profile, in combination with the display’s profile, the projection on the screen should be exactly the same as what we started with. And by combining with the printer’s profile during printing, the result on paper will look the same too.

This functionality has long been missing from the GIMP, but now we have it. Admittedly, it is of limited usefulness while we are limited to 8 bits per channel, because the application of a color profile results in what is called banding – when you squeeze one colorspace into another, sometimes colors close together map to the same color in the output, which means that we lose some quality. However, this is a massive step forward over what we have had until now.

Do you RPM?

I have been talking to someone recently who is looking for some help packaging GNOME for an RPM based distribution. The distribution has some special things going for it which make the task a bit more interesting…

If you have some experience making RPMs, and you like trying out new distros, drop me an e-mail, and I’ll put you in touch with the guy.

Mac keyboard update

Many thanks to Frank Murphy for an updated fr keymap to use for Ubuntu. Now I just need to figure out how to get the bootloader back…

For shame…

I finally got around to backing up all my data, music & photos for the past few months this evening, with the intention of installing Ubuntu on my PPC, and kicking the MacOS X habit.

Alas, I’m back in MacOS X again. I wa going to install it in any case, because my wife likes it, but given that I can’t type # or @ in Ubuntu on a standard Macintosh French keyboard, I can’t see myself booting into it regularly for the next while. When I have more time, I’ll maybe try to figure out XKeyMap stuff again.

Also, I was a little annoyed that the (marginally unusual) case of English language and a French keyboard would cause so many issues. During the installation, I was asked for a country, language preference, and keyboard config (which worked fine). Then after the first boot into GDM, my keyboard was in US layout (very useful when you have numbers in your password).

And after logging in, and configuring the keyboard for myself, I still have no idea how to configure the keyboard layout system-wide, even though it’s obvious that I’m not going to have a different keyboard plugged in for each user…

I’m not quite a JWZ’s “last time”, but I have had far too much trouble configuring keyboards, sound cards and fonts in my short life, once every 4 or 5 years is more than enough, thanks.

Still no titles

There is a discussion going on over at foundation-list about membership of the foundation, which has gotten interesting. There was a good comment from Luis Villa:

[You] assume ‘more members’ == ‘good’, and
I’m not sure I follow that, given that much of the current membership
is apathetic and uninvolved [in the foundation] and increasing the numbers doesn’t actually solve that. I’d prefer we figure out why we have membership (besides the obvious legal/voting reasons), what we offer the membership, and what the membership offers ‘us’ (the community, the foundation, etc.), then talk about having a membership drive if it is still appropriate.

I get what Luis is saying, but I think the problem is more one of perception that reality. It seems to me, when I look around, that lots of people are working on communication, advocacy, marketing and all of the other things that the foundation is supposed to do. The foundation is not the board, after all, even if it’s sometimes easy to think that.

What do you think? What should the foundation represent? What does it represent to you? What’s wrong with it? How can we fix it?

KDE in Vienna

Congratulations to our freedom-loving brothers and sisters in KDEland on their success – KDE and Debian has been adopted by the city of Vienna as an official supported operating system (with about 5000 client machines expected to switch). A nice win for free software.

Software patents

Jordi:

The commission can’t come back on this one. The process is a bit twisted, but this is the end of the road. The process is

1. The commission writes the law
2. In parallel, the council of ministers and the parliament vote the law, possibly making reccommendations for changes
3. The commission reviews the reccommendations, and approves or refuses them
4. The council of ministers votes on the resulting text (or a modified version they agree on by qualified majority)
5. The resulting text gets sent to the parlianent, where they can accept the text presented, make amendments to it, or reject it as presented. Any modification or rejection requires an absolute majority of MEPs
6. If they make changes and accept it, the resulting text must be approved by an arbitration committee made up half of MEPs and half of ministers on the council of ministers

We were at the second last stage today, and if the law has been rejected, the only option that the commission now has is to modify the law, and go through the whole process again (the infamous restart requested by JURI some months ago).

Given the completely polarised result of the vote, I’m now wondering whether JURI (which was favourable to the parliament’s position some months ago) rejected all of Rocard’s amendments to polarise the parliament and avoid a dodgy law going through on a split decision.

Fair play to the FFII. I hate to bring it up in our hour of glory, but doesn’t this mean we stay at the current ambiguous “software patents are not allowed, but are granted anyway” situation, though? Wasn’t one of the goals of this law to regularise the situation one way or the other?

Live8

For those of you who don’t know yet (haven’t seen anyone blogging about it), the Live8 concerts are on today. Afterwards, there’s the Long March to G8 going from Mondon to Edinburgh, in time for the G8 meeting on Wednesday.

This is a bunch of people trying to change the world by people power (a bit like us). Worth a mention, worth support. If you can go to the concerts, have a laugh. If not, sign the petition, maybe go to Edinburgh…

I have some nice news today (unusual for a Monday afternoon).

A couple of months ago I went around a few French magazines hawking the idea of a regular GNOME column with a mix of original articles and translated GNOME Journal content.

Denis Bodor and Fleur Brosseau at Diamond Editions were interested, and so starting next month, we will have a new column called “GNOME Corner” in the French magazine “Linux Pratique”, a magazine aimed at Linux beginners still discovering the joys of free software.

The first issue includes 2 articles from the GNOME Journal (a little bird tells me that Claus Schwarm is actively hunting for article authors), Audio CD Ripping and Burning in GNOME by Ken VanDine of Foresight Linux and Evolution 2.2 by Jorge Castro (Jorge, if you’re reading, please mail me, I haven’t got an e-mail address for you). Both articles were translated by GNOME-fr member Laurent Richard.

Congrats to all involved. More exposure in print media is necessary if we want to improve GNOME’s image among hackers, Linux beginners and ourselves.

Since GNOME Journal articles won’t always fill the space allotted to us (4 pages per month!) I also hope to poke some people for original articles in French. Anyone interested please contact me.

Update: I just noticed that there is a GUADEC report in this month’s GNU/Linux Magazine France as well.

PS. Help Seth! I can’t add a title!

Advogato.org introduced me to the world of blogging a little over a year ago. Now I can’t figure out how I lived without a blog before then.

Image uploads are what have finally moved me away from it (that and blogs.gnome.org opening up shop), but since I’ve decided to move I’ve had a few problems. First, I no longer exist and haven’t yet managed to get hold of Raph to get stuff fixed. Thankfully, my old blog entries are safe. But the mod_virgule import didn’t work right with my account, so I only managed to import the 10 most recent entries via RSS. Bummer.

Hopefully I can get my planet feed updated to point here soon (go Jeff!).