Sorry for late reply.
It is possible to do this with Ghostscript but not with the ink_cov device as you say. However, it is possible to do this by measuring the coverage on tiff files exported by Ghostscript by using Python. Attached are two scripts. One batch file and one python script.
The batch file:
"C:\Program Files\gs\gs9.50\bin\gswin64c.exe" -dNOPAUSE -dNOCACHE -dBATCH -dNOSAFER -sDEVICE=tiffsep1 -r300x300 -sOutputFile="C:\tmp\%~nx1_p%%03d.tif" %1
"C:\Program Files\Python37\python.exe" "C:\Xerox\FreeFlow\Core\00000000-0000-0000-0000-000000000000\Data\Scripts\inkcov.py" %~nx1
The batch file does two things:
It first calls Ghostscript and saves the PDF as .tif files to C:\tmp using the tiffsep1 device. One tif for each separation, also for spot colors.
It then runs the python script that looks like this:
import numpy as np
report = open('C:/tmp/' + sys.argv + '.txt',"w+")
files = os.listdir('C:/tmp/')
for pic in files:
if sys.argv in pic and '.tif' in pic:
img = cv2.imread(os.path.join('C:/tmp/', pic), 0)
assert not isinstance(img,type(None)), 'image not found'
inkcovIMG = img/np.full(img.shape, 255)
#print (round(100*(1-np.mean(inkcovIMG)), 1))
report.write(str(round(100*(1-np.mean(inkcovIMG)), 1))) # Coverage in percent with one decimal
The python script uses something called numpy and opencv to be able to calculate the ink coverage for each tif file in C:\tmp corresponding to the specific job and then writes the result to a txt file with the job name. To get the report as csv or similar some more scripting has to be done.
To install python as required for this you could use this as a reference: https://www.youtube.com/watch?v=d3AT9EGp4iw
You can then run this is an External Process in FFCore pointing to the batch file and use the default parameters. However, only $FFin$ is necessary in this case.
Ghostscript has a device named ink_cov that you could try.
This script that you can use in an External process in FFCore will run ink_cov on a pdf and save the report to C:\temp using the job name.
"C:\Program Files\gs\gs9.50\bin\gswin64c.exe" -o - -sDEVICE=ink_cov %1 > C:\temp\%2.report.txt
The report will be a text file with the CMYK coverage values for each page like this:
50.62684 42.02598 25.07010 19.32347 CMYK OK
4.18561 5.82315 9.58333 3.07993 CMYK OK
and so on.
Is this what you are looking for? This is from Callas 10. Presently, FFCore support Callas 10. We are working on support for Callas 11.