Public bug reported:
I've been trying to calibrate my printer in Ubuntu 18.04.3LTS with
gnome-control-center:
Installed: 1:3.28.2-0ubuntu0.18.04.5
Candidate: 1:3.28.2-0ubuntu0.18.04.5
Version table:
*** 1:3.28.2-0ubuntu0.18.04.5 500
The least documented part of printer profiling is printing the target. Every
guide says turn off printer profile calibration, but no-one tells you how.
Through trial, error and a lot of paper and ink it seems to me as though the on
/ off button next to the printer description does nothing.
If the user deletes all existing profiles the field reads Not calibrated and no
button is displayed, though on a reboot this changes to a button showing colour
management (CMS) on and two default profiles are displayed (default RGB and
default grey) with RGB selected. The output of these two states is identical.
If the setting is default RGB profile with no others loaded, then changing Cups
in a browser to Colour Correction: uncorrected refreshes the state to Not
Calibrated, though this is the only time I could force this. Setting Cups to
Colour Correction: high accuracy does result in an altered output from the
printer. I am guessing this is no colour profiling being applied.
However if Cups Colour Correction: uncorrected is set, and a profile is loaded
in Device Colour Profiles the output from the printer is the same whether or
not the CMS on /off button is pressed. I think this is the result of the
profile applied by Device Colour Profiles in either case.
Similarly, using Cups Colour Correction: High Accuracy and a profile loaded in
Device Colour Profiles, the printer output is the same whether or not the CMS
on /off button is pressed, though the output is different from the preceding
example. I presume this is the result of two colour transformations being
carried out.
The attached images of my printer output should hopefully help explain this
situation.
** Affects: gnome-control-center (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "A series of jpgs showing the process"
https://bugs.launchpad.net/bugs/1855615/+attachment/5310861/+files/printer%20output%20pictures.zip
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https://bugs.launchpad.net/bugs/1855615
Title:
Device colour profiles - on / off button not working Ubuntu 18.04.3LTS
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