Technical Blog of Richard Hughes

Work on gnome-color-manager continues. Display, scanner and camera profiling seems to work very well now, but I would really like to move on to creating profiles for printers. To do this I need to buy some expensive kit, something like a ColorMunki. If anyone has one of these sitting in a draw being unloved, it would be all I need to add support to gnome-color-manager. It’s not something I can expense, as it’s not really part of the day job. Anybody?

Does anybody know of any standard CMYK color space ICC profiles that exist in the wild? I’m hoping to convince the copyright owners to release them under a free licence. The Adobe, ECI and IDEAlliance profiles are all really non-free and thus we can’t ship them by default. Thanks!

I’ve been hacking at gnome-color-manager for a few weeks now. We had a first release last week, and we’ve since been adding in more new features and a couple of nice bugfixes. But that’s not what this blog post is all about.

A typical target

To calibrate a device, you need to scan in (or take a photograph of) a very accurately printed image. These printed images are called “targets” and usually come with a CD-ROM of the calibration data for that batch, or a URL of where to get the calibration data from.

Now, the number of people wanting to use a calibration target is going to increase in the future, as they’ll want to have a color-calibrated workflow whilst using Linux. These random CD-ROMs that get lost and URLs that might vanish don’t seem so easy to use when you’re calibrating 200 workstations, maybe using a different type of target for scanner, camera and film. And re-calibrating them all two years later doesn’t look like fun either.

So, ideally, we would ask the manufacturers of the calibration data (just big text files of numbers), and we could ship it in a shared package, that the distros can ship. Unfortunately, a lot of the targets in existence have NDA or horrible licensing terms shipped with them. This makes distros like Fedora that can only ship free software and content sad.

Enter Wolf Faust. He’s the bloke that’s been shipping high quality IT8 targets all over the world for the last few years. He’ll ship you just a single target (there is no minimum order), so it’s enthusiast friendly. The pricing is cheap (25 Euro) and postage and packaging is reasonable (5 Euro), which makes him the obvious choice for someone that just needs a target or two to calibrate their photographic or graphics workflow.

Wolf Faust has just released his entire set of calibration data under a free license. This means we can ship it in a distro package, so that calibrating a scanner is as simple as borrowing a target from a friend and taking a photo of it and then selecting a target name from a GUI drop-down. No need to fumble about with CDROMs or downloading the correct target from a website, now it just works.

Now, I guess Wolf has realized by making the calibration data “free” content, he’ll sell more targets; and I hope he does. If you make it easier for people to use your product more people will buy it for sure. It makes no sense keeping this data secret and wrapped up in legalese. It might not be much, but this for me is an advance of freedom, as much as just-another-package in a repository.

Note, gnome-color-manager will install shared-color-targets automatically using PackageKit if you try to calibrate a device and it’s not already installed. We’ll do the first official release of shared-color-targets just after Christmas.

A few days ago I created the shared-color-profiles project. This contains redistributable ICC profiles from different vendors (some free, some non-free). The configure script allows a distro to install just the profile types that are acceptable. In Fedora, that boils down to the profiles in public domain, but we’re hoping to add CC-BY-SA and CC-BY-ND manufacturer submitted profiles really soon. At the moment I’ve added Adobe, Argyll, ECI, ICC and IDEAlliance profiles. A few people are interested in creating profiles for common cameras models, although this would probably be a community supported effort rather than a vendor-supported effort. Anyway, doing this allows us to define proper color working spaces and default spaces to use in applications.

Anyway, if you know of any vendors or standard bodies that have released profiles that allow distribution as part of a combined package, or as CC-BY-foo or public domain then please let me know as a comment on this blog. Thanks.

Next Monday I intend to release the first supported version of gnome-color-manager (2.29.1) into the wild.

There have been quite a few new features added to git master recently, and very many bugs squashed. I wanted to thank Pascal de Bruijn for the hours and hours of regression testing he’s been doing, and quite a few other people on the mailing list that have also been reporting bugs before the release. There are quite a few translations already committed, so the first release should look really good.

New features added in the last couple of weeks:

• Ability to support and manage “disconnected” devices
• Cairo CIE widget showing gamut ranges
• Ability to delete and import existing profiles
• Adding of the rendering intent settings to the DBus interface for applications to use

More testing is always welcome. Thanks!

And so, long story short, we decided to revert the change for F12.

Part of being an open source maintainer (and also my job at Red Hat) is to ignore trolls, but some of the messages I was getting yesterday were just personal attacks and abuse. That’s not cricket at all.

GNOME Color Manager now a mailing list – It’s for discussion about colour management in GNOME, and that sort of thing.

Late last night, after a few hours of intense refactoring (to allow udev based devices, as well as xrandr based devices) we got the initial scanner support working:

Scanner support

This lets us support printers and digital cameras pretty easily too. At the moment we just need to figure out how to make gnome-scan make a scan for us and save it in tiff format, and then we can get the calibration working for all types of scanners. Of course, you need a precision printed reference image, but you can get these pretty cheaply from Wolf Faust.

Then, we need to work with the gnome-scan guys to agree an interface so that gnome-scan knows what profile to use for each device. Either a library or DBus interface (with calls in either direction) are being considered, although I think the session-activated dbus interface is probably going to win. There’s still quite a bit of integration work to make CUPS ICC profile aware, but that’s on the list after scanners are working. After all, you need a calibrated scanner to calibrate the printer. Help is always welcome, so please checkout the code and help find bugs.

GNOME Color Manager now has a website. The mailing list will be set up soon, which means we can start building a community.

I’ve also recently completed the calibration integration, using the great ArgyllCMS to do the heavy lifting. This means it’s literally two clicks (with no options!) to generate an accurate screen profile with hardware that costs less than $50. And it only takes about 15 minutes. Anyone that takes photos or cares about colour accuracy should really invest in one of these things.

Calibration stage 4 of 5

Also, a few people have been telling me to just write a GNOME front end for Oyranos and scrap what’s already been done. While I think Oyranos is a great project, I needed something that “just worked” and did the bare minimum integration without a hundred configuration options or integration points. I’ve also been told that some parts of colour management are heavily patented, and so I’m going to keep things as simple as possible for now so gnome-color-manager can be used in as many places as possible. If the Oyranos guys want to hook into gnome-color-manager then that would be great, but I think for now, GNOME Color Manager should aim to do much less than what the Oyranos guys have been trying to achieve.

Well, you could say I’ve been busy. I’ve had a couple of days off this week, and instead of relaxing like normal people, I wanted to fix ICC profiles on GNOME.

First the hard bit. You have to go to your screen vendors website, and download the “drivers” for your monitor. They’ll likely come in a zip file with other junk like .inf, .cat and other windows driver stuff. Somewhere in there should be a .icm or .icc file which contains the data you need specific for your monitor.

Double click on a ICM or ICC file.

Then go to System->Prefrerences->Color Profiles and select the correct file for your monitor. There are also some other test files you can play with.

The default display

Then you can set any gamma or contrast or brightness settings if you wish. The gamma defaults to 2.2 just like newer Apple systems and Windows XP, but if you don’t like this you can set it back to 1.0.

The advanced display

You’ll need shared-mime-info from git master (for the double click to work) and gnome-color-manager from gnome git.

There’s still lots of work to do, such as:

• New project icon
• Help and man documentation
• A website of some description
• A mailing list
• The calibration button to be wired up with hardware devices

I’ve ordered myself a Pantone Huey hardware calibration device, and soon hope to have this wired up to gnome-color-manager to make accuratly calibrating a device as easy as a single click.

Now, I’m all out of time for this little bit of fun, as I have to return back to fixing PackageKit and DeviceKit-power for the impending F12 release, but if anyone wants to help me with this I would be very grateful.