Color Calibration in Kubuntu (ColorHug)

Jun 19, 2024 3 min read howto

A long time ago, I bought a ColorHug2. Unfortunately, the project shut down in 2020. But the device is still usable, even on brand new distributions. Since it’s open hardware and software, you can still hack on it and even modify the firmware.

In Kubuntu 24.04 to apply an existing profile to a monitor, just install apt install colord-kde. Then use the “Color Management” section in System Settings under Hardware.

To build a new profile with a ColorHug:

apt install colord-kde colorhug-client argyll

colorhug-client will give you some tools to manage the ColorHug and should provide any drivers needed by argyll to use the ColorHug. You can at least use colorhug-cmd to sanity check your device:

user@thing:~$ colorhug-cmd get-leds
LEDs: 0
user@thing:~$ colorhug-cmd self-test
user@thing:~$ colorhug-cmd get-temperature
Temperature: 27.250000

Use the dispcal application from argyll to build an ICC profile. Somewhere, I read you should set your display’s brightness to 80% when calibrating. Seems reasonable, but don’t take my word for it.

Here’s what calibration looks like from the command line. I ran 5) Check all first, then 7) Continue on to calibration:

user@thing:~$ dispcal -o new-profile.icc
dispcal: Warning - new_dispwin: Expected VideoLUT depth 8 doesn't match actual 10
Place instrument on test window.
Hit Esc or Q to give up, any other key to continue:

Display adjustment menu:
Press 1 .. 7
1) Black level (CRT: Offset/Brightness)
2) White point (Color temperature, R,G,B, Gain/Contrast)
3) White level (CRT: Gain/Contrast, LCD: Brightness/Backlight)
4) Black point (R,G,B, Offset/Brightness)
5) Check all
6) Measure and set ambient for viewing condition adjustment
7) Continue on to calibration
8) Exit
Doing check measurements

  Current Brightness = 441.78
  Target 50% Level  = 83.703, Current = 93.681 (Aprox. Gamma 2.24), error =  2.3%
  Target Near Black = 4.4178, Current = 4.3661, error = -0.0%
  Current white = x 0.2837, y 0.3422, VDT 6750K DE 2K 18.8
  Target black = x 0.2837, y 0.3422, Current = x 0.2797, y 0.3384, error =  2.14 DE

Press 1 .. 7
1) Black level (CRT: Offset/Brightness)
2) White point (Color temperature, R,G,B, Gain/Contrast)
3) White level (CRT: Gain/Contrast, LCD: Brightness/Backlight)
4) Black point (R,G,B, Offset/Brightness)
5) Check all
6) Measure and set ambient for viewing condition adjustment
7) Continue on to calibration
8) Exit
Commencing display calibration
The instrument can be removed from the screen.

This will produce two files: new-profile.icc.cal and new-profile.icc.icc

You want the .icc.icc file.

Then go to the KDE system settings application. Select Hardware, then Color Management. Click on “Import Profile” and import the .icc file you just created. Then select your display, click “Assign Profile” and assign that profile to it. Click “Apply”. Success!