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

[Rich Freeman <rich0@gentoo.org>]

On Tue, Sep 8, 2015 at 2:42 PM, Mick <michaelkintzios@gmail.com> wrote:
> On the same hardware I noticed that a CMYK photograph converted to sRGB looked
> mostly the same (indistinguishable) on Linux, but the sRGB colours were
> brighter on MSWindows.
>

If everything is working correctly then the CMYK original and sRGB
copy should look identical, with the exception of any out-of-gamut
colors (as I understand it, very little of CYMK is out-of-gamut for
sRGB).

If they're not identical then something is wrong, so I wouldn't assume
that Linux is at fault (though it could be if the file looks wrong
when created on Linux and viewed on another OS, and both OSes are
using calibration).

Imagine if your original email read like this:

On the same hardware I noticed that when I saved my simple OpenOffice
document in MS Word format in Linux, and then opened the MS Word file,
the text was identical.  I tried doing the same thing on both Windows
and OSX and in both cases there were lots of weird symbols in the text
of the document.  What is wrong with my Linux OpenOffice program? Why
doesn't it mke my dcment lok lik ths like the other OSes?

or like this:

On the same hardware I noticed that when I copied a file from a fat32
USB stick to an ext4 USB stick the md5sum of the files remained
unchanged.  However, if I perform the copy on OSX or Windows the
md5sum changes.  What is wrong with my linux filesystem drivers?  Why
doesn't it randomly modify my data when I try to copy it?  And, darn
it, why does it seem like I never have to reboot the thing to keep it
from crashing?

Now if one OS or another isn't properly calibrated to your monitor the
same file could have different appearances, and if for whatever reason
your viewer for the CYMK file applies calibration data differently
than the viewer for the sRGB file that would also cause issues.  So,
the problem might be in the viewing of the files, or in the
conversion.  Based solely on the testing you performed I can't really
be sure which if any of your conversions are being done correctly.
The file might appear unchanged on Linux but it could be a result of
cancelling errors in the creation and rendering of the file.

However, since the whole goal of the conversion process is to avoid
making visible changes to the file to the greatest degree possible,
I'd tend to look at the other OSes for problems first.

-- 
Rich