Re: [gentoo-user] CMYK comparison to sRGB between platforms

[Mick]

On Sunday 27 Sep 2015 09:58:43 Peter Humphrey wrote:
> On Saturday 26 September 2015 16:11:04 Mick wrote:
> > Thank you all for your answers.  They guided me to do some reading in
> > this field, which is quite a science all on its own!
>
> --->8
>
> > Peter's description does not mention which application loads the .icc
> > file that the hughski creates, but I'm guessing there must be something
> > that does read it, if the monitor settings are indeed altered.
>
> As far as I remember, it's the colorhug's own program that sets the monitor
> at the end of its calibration process. After that, the monitor has kept
> those settings and hasn't needed any further tweaking.
>
> I do have the two .icc files in .local/share/icc:
>
> $ ls -l .local/share/icc
> total 28K
> -rw-r--r-- 1 prh prh 1.2K Sep  9 16:51
> edid-fbec4f9c1804ea718b6e1b585fc234ad.icc -rw-rw-r-- 1 prh prh  21K Sep 10
> 10:41 GCM - Samsung - SMS27A350H - unknown (2015-09-10) [04-58-44].icc
>
> /usr/bin/file shows them both as "ColorSync ICC Profile". I don't know why
> there are two, nor why they have such different sizes.

I'm guessing that the 'edid-fbec4f9c1804ea718b6e1b585fc234ad.icc' was 
extracted from your monitor's EEPROM chip through the i2c bus and saved on 
disk by the LiveCD you ran, but the 'GCM - Samsung - SMS27A350H - unknown 
(2015-09-10) [04-58-44].icc' was generated by the colorimeter during your 
calibration exercise.

I'm also guessing that the smaller size of the first file is because your 
monitor's EDID is of an earlier version, e.g. EDID-v1.1 or some such, which 
used to only contain a 128-byte data structure.  I seem to recall that very 
early EDID versions didn't even contain colospace and Gamma data, but may be 
wrong.

These are the sizes :

ls -n ~/.local/share/color/icc/devices/Display/
total 800
-rw-r--r-- 1 1001 1001   1944 Sep 18 18:16 ACI ASUS VS239 
EALMTF200702_edid.icc
-rw-r--r-- 1 1001 1001   2016 Sep 18 18:16 Dell Computer DELL ST2320L 
MP82K0712EJL_edid.icc
-rw-r--r-- 1 1001 1001  20884 Sep 18 19:01 P2311H 2012-06-20 2.2 MQ-HQ 
3xCurve+MTX.icc
-rw-r--r-- 1 1001 1001 783804 Sep 18 19:02 PA248 2015-04-18 S XYZLUT+MTX.icc

The first two are from the monitors' EDID content, the latter are the profiles 
I downloaded from the Taxi DB.  Some of these contributors' profiles were 
created with spyder or other expensive colorimeters, so I am surmising that 
they capture more data points and contain more information, than the 
manufacturers EDID which is primarily contains other than colorspace and Gamma 
data.


> Maybe I'm mistaken and KDE is reading what it needs at startup from those
> Files. I'll try moving them and see what happens.
>
> > With the monitors sorted as best as I could adjust them manually I loaded
> > the icc files with Kolor-manager.  I could not see any change in the
> > colors displayed by the monitors.  They are both wide gamut monitors, so
> > perhaps the RGB changes were within the narrower RGB spectrum and that's
> > why I did not notice a difference - not to mention that my eyes are not
> > they used to be. :p
> >
> > Having done all this, I revisited ImageMagick.  I ran identify -verbose
> > and discovered that the original jpg image did not have an embedded icc
> > profile. So I reran the command specifying a cmyk profile for the input
> > file and an sRGB for the output file.  The result is now satisfactory
> > and comparable on all operating systems.
> >
> > I am still a bit unclear if on non-KDE dekstops xserver will pick up any
> > icc files for the monitor from ~/.local/share/color/icc and load them at
> > start up all on its own, or if any additional software is necessary to
> > achieve this.
>
> Yes, I'm also unclear on this.

-- 
Regards,
Mick