USING THE COLORMATCH SCRIPT FOR ARGYLLCMS ICC …

USING THE COLORMATCH SCRIPT FOR ARGYLLCMS ICC CREATION OF RAW/JPG PAIRS

So this modification of the colormatch script was part of a wider experiment to run a Linux version of darktable on my Windows PC.

I had previously enabled WSL2 on Windows and installed Ubuntu 20.04 from the Microsoft app store.

This worked fine but I only had a terminal version of Linux.

So I followed the instructions from this video. There are lots of versions of this approach with small differences.

This worked pretty much out of the gate. I built and installed darktable from git and it runs smoothly.

I had wanted to try this just to see if it was possible and also just to compare the versions between Windows and Linux as there are glitches from time to time that appear in one but not the other.

Okay so now I had this linux environment and I was poking around and found Pascal's colormatch script on his git repo. . There are extensive notes and a description of the process for capturing and processing the images. Basically you need to do a linear noop export to a tiff file for your raw. Its not always clear but in darktable this means setting your input and output profiles to be the same. This creates a passthrough for your raw file. Details are provide on the git webpage.

I read through it and tried initially to print out the color tiff for his IT8 reference chart and use the script as is. My laser printer at work is a decent one but it really could not render a decent enough copy to try this out with. So I started to look at the script to try to figure it out. I knew a bit about ArgyllCMS so I could basically follow it but I am still not certain how the blending of the two images actually happens in the code. I thought could it be modified to work with my color card (Datacolor Spyderchecker24)

The script itself requires very little modification. You can get it here

There are three variables to address. First, where your Argyll reference files are installed (Argyll needs to be installed but I think it is part of the Ubuntu install if not then just install it -- sudo apt-get install

-y argyll)

Default: ARGYLL_REF=/usr/share/color/argyll/ref

What color space your jpg file was created in and so what file the script should reference when running Argyll. Options are srgb and adobergb from the Argyll reference directory. My jpgs are usually srgb so that is the change I made

COLORSPACE=${ARGYLL_REF}/ClayRGB1998sRGB.icm # ${ARGYLL_REF}/sRGB.icm

And you need to define the names of the cht layout file for your color checker and provide the matching reference values in a cie format file that Argyll understand, eg Spyder24.cht and Spyder24.cie.

Running the script is straightforward using the tif files as input:

./colormatch camera(jpg).tif raw.tif

The script will prompt you for a description which will be what the icc profile shows as in darktable and it will add Colormatch- as a prefix to this description when it saves the file. After entering the description press enter to run and that is it. The sript reads in the tif images using the scanin command and then does some manipulations (the parts I don't fully understand) and then it run the colprof Argyll command with the following optins which you can edit or add to to create different types of profiles

colprof -A "${MAKE}" -M "${MODEL}" -D "${DESCR}" -C "${COPY}" -r 1 -q h -b n -a x ${OUTPUT}

You can visit the Argyll site to see what these options are and how you might modify them



That is basically it to use the icc file that is created it must be copied to the \color\in\ folder in your darktable config file. By default this is in Users\"username"\Appdata\darktable\color\in for windows. I am not sure as I write this where it is in Linux. Depending on where you have installed and how you have it configured but something like home\usr\.config\darktable\color\in???

If you rename the script you will have to give the copy execute privileges using chmod +x "colormatch_renamed". No quotes in the command and use you new name for the script. I have copies that run the CC24 colorchart, the Spyderchecker24 chart and versions of those where I modified the colprof command line in the script to modify the resulting icc.

The final and most important part is that you must change the format in the Argyll cht/cie files or your own cht/cie files to match the format of the colormatch cht and cie used in the script. So the script requires minimal change. One thing I did find is you need to edit it in nano or some linux editor. Window notepad will mess with the bash script. I grabbed nano as it is dead easy to use.



Modify cie and cht files to allow for double digits. The default 1 needs to be entered as 01, 2 as 02 etc etc.

Also add a 0 before the 1 and 6 in the cht file header and add A1 as A01 A2 A02 etc in both cht and cie files.

The next pages will show you sample files for the Spyderchecker24 in the normal way that you see them in Argyll and as they need to be modified. The modified parts will be highlighted in bold. And that is basically it. Depending on your layout in the cht file it will expect the color chart in either portrait or landscape. The file I have modified for the Spyder24 are for portrait orientation with the white patch top left. The colorchecker files are for landscape with the white patch lower left so essentially 90 degrees counter to the spyderchecker. I may have overlooked something but these are the basic steps and modifications that I have used.

(A) Argyll Spyder24 CHT file

BOXES 25 F _ _ 11 11 405.5 11 D ALL ALL _ _ 415 619 X A D 1 6 88.5 88.5

405.5 609.5 11 609.5 0 0 0 0

11 11 102 102

BOX_SHRINK 8.0

REF_ROTATION 0.0

XLIST 8 11.0 1.0 1.0 99.5 1.0 1.0 113.0 1.0 1.0 201.5 1.0 1.0 215.0 1.0 1.0 303.5 1.0 1.0 317.0 1.0 1.0 405.5 1.0 1.0

YLIST 12 11.0 1.0 1.0 99.5 1.0 1.0 113.0 1.0 1.0 201.5 1.0 1.0 215.0 1.0 1.0 303.5 1.0 1.0 317.0 1.0 1.0 405.5 1.0 1.0 419.0 1.0 1.0 507.5 1.0 1.0 521.0 1.0 1.0 609.5 1.0 1.0

EXPECTED XYZ 24 A1 86.79568693 90.10426176 94.19984662 A2 55.08051541 57.46423605 60.28298406 A3 33.18279082 34.70711744 36.3096224 A4 17.31179393 18.1023397 18.9062329 A5 7.444384111 7.793939114 8.075868179 A6 2.236744998 2.283545551 2.594402184 B1 10.45228637 16.11116713 35.44158597 B2 29.89764083 18.83193867 28.6689314 B3 61.60693164 63.3191174 8.276546214 B4 21.9270034 11.8957815 4.128802731 B5 13.60755739 22.10666942 8.711745906 B6 5.168338634 4.33519734 23.36537978 C1 38.46785597 29.17981796 4.942695621 C2 10.40622338 9.976377158 34.08444037 C3 27.86668281 18.26003917 12.69484363 C4 7.328143078 5.791413539 14.38375528 C5 34.7946419 44.33222656 10.60860691

C6 49.22893482 43.14016418 6.669930906 D1 29.79588748 41.02009619 42.90228052 D2 23.13852821 22.33437582 43.28206274 D3 9.786320619 12.51940659 6.24309986 D4 15.69068648 17.44829971 33.36667992 D5 37.80428753 34.17343186 24.19994549 D6 10.36083441 9.075889655 5.537485335

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