Pages: [1]   Go Down

Author Topic: Argyll and SpyderPrint Lab data  (Read 1128 times)

bordac

  • Newbie
  • *
  • Offline Offline
  • Posts: 2
Argyll and SpyderPrint Lab data
« on: August 23, 2019, 03:58:49 am »

Hello everybody.
I'm trying to build profile by Argyll using Spyder Print measurements data (Lab).

I extracted and prepared Lab value from SpyderPrint xml file and encapsulate it to a .ti3 Argyll file:

CTI3   

DESCRIPTOR "Argyll Calibration Target chart information 3"
ORIGINATOR "Argyll printread"
CREATED "Tue Aug 20 19:16:40 2019"
DEVICE_CLASS "OUTPUT"
COLOR_REP "iRGB_LAB"

NUMBER_OF_FIELDS 7
BEGIN_DATA_FORMAT
SAMPLE_ID LAB_L LAB_A LAB_B
END_DATA_FORMAT

NUMBER_OF_SETS 441
BEGIN_DATA
1 25.13 10.5 14.31
2 24.51 21.49 -2.15
3 21.54 -24.67 -17.43
....
END_DATA


but when i trying to build profile by command:
colprof -v -D"Description" -qm -S AdobeRGB.icm -cmt -dpp MyTi3File

I get error:
colprof: Error - Input file doesn't contain field RGB_R

How to build RGB data from Lab or how make profile without thise RGB data?
Logged

Doug Gray

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2197
Re: Argyll and SpyderPrint Lab data
« Reply #1 on: August 23, 2019, 11:00:58 am »

Hello everybody.
I'm trying to build profile by Argyll using Spyder Print measurements data (Lab).

I extracted and prepared Lab value from SpyderPrint xml file and encapsulate it to a .ti3 Argyll file:

CTI3   

DESCRIPTOR "Argyll Calibration Target chart information 3"
ORIGINATOR "Argyll printread"
CREATED "Tue Aug 20 19:16:40 2019"
DEVICE_CLASS "OUTPUT"
COLOR_REP "iRGB_LAB"

NUMBER_OF_FIELDS 7
BEGIN_DATA_FORMAT
SAMPLE_ID LAB_L LAB_A LAB_B
END_DATA_FORMAT

NUMBER_OF_SETS 441
BEGIN_DATA
1 25.13 10.5 14.31
2 24.51 21.49 -2.15
3 21.54 -24.67 -17.43
....
END_DATA


but when i trying to build profile by command:
colprof -v -D"Description" -qm -S AdobeRGB.icm -cmt -dpp MyTi3File

I get error:
colprof: Error - Input file doesn't contain field RGB_R

How to build RGB data from Lab or how make profile without thise RGB data?

In short, you can't.

You must combine the RGB data that the printer used to create the target you measured and add it to the CGATs file. The colors that RGB data produces is specific to the printer you used and will vary a lot from printer to printer. Creating a profile is a way of determining the RGB values to be printed from PCS Lab space and it is not possible to determine the printer's RGB values from the measured Lab values.

See Patrick's explanation and suggestion below which is quite good.
« Last Edit: August 23, 2019, 06:16:32 pm by Doug Gray »
Logged

Pat Herold

  • Full Member
  • ***
  • Offline Offline
  • Posts: 161
Re: Argyll and SpyderPrint Lab data
« Reply #2 on: August 23, 2019, 04:28:43 pm »

Imagine your RGB data are the numbers on the face of a toaster, and also suppose that the color of toast that you want is represented by Lab values.  You can't actually convert the color of toast to a setting on your toaster until you know something about the toaster - until you've made a "profile" of how the toaster toasts.

http://www.colorwiki.com/wiki/The_Color_of_Toast

But to answer your problem:
There is usually a reference file that is associated with a target print that you've measured.   The RGB values in that file have to be married up with the Lab values you've measured.  This can be done with a spreadsheet program like Excel.   There are other methods too, if that does not work.
Logged
-Patrick Herold
  Tech Support,  chromix.com

bordac

  • Newbie
  • *
  • Offline Offline
  • Posts: 2
Re: Argyll and SpyderPrint Lab data
« Reply #3 on: August 24, 2019, 02:33:52 am »

Good day.
Thank You everybody for answers.

I got RGB value from my .ti2 file and inserted in .ti3 file and add my measured lab data (by Excel):

CTI3   

DESCRIPTOR "Argyll Calibration Target chart information 3"
ORIGINATOR "Argyll printread"
CREATED "Tue Aug 20 19:16:40 2019"
DEVICE_CLASS "OUTPUT"
COLOR_REP "iRGB_LAB"

NUMBER_OF_FIELDS 7
BEGIN_DATA_FORMAT
SAMPLE_ID SAMPLE_LOC RGB_R RGB_G RGB_B LAB_L LAB_A LAB_B
END_DATA_FORMAT

NUMBER_OF_SETS 441
BEGIN_DATA
1 "A1" 47.45098 23.13725 0.00000 25.13 10.5 14.31
2 "A10" 57.64706 17.64706 38.43137 24.51 21.49 -2.15
3 "A11" 0.00000 59.60784 48.23529 21.54 -24.67 -17.43
....
END_DATA


and built profile without error.

Another way is use argyll fakeread tool and
create a .ti3 file from .ti1 file, and paste L*a*b* values into the .ti3 file.

I hope it is correct =)
Logged

Pat Herold

  • Full Member
  • ***
  • Offline Offline
  • Posts: 161
Re: Argyll and SpyderPrint Lab data
« Reply #4 on: August 26, 2019, 01:39:08 pm »

There you go!  Good job.
For those reading this post in the future, another way to get a reference file when all you have is the image of the chart, is to bring the image into the Worksheet of ColorThink Pro.  You can create a custom grid for sampling the rows and columns of the target image, and it will allow you to save out the RGB or CMYK values.  You can then put them together with your measurement information in Excel as bordac has done.
Logged
-Patrick Herold
  Tech Support,  chromix.com
Pages: [1]   Go Up