[argyllcms] Re: How is delta E calculated in colprof?
- From: Stephen T <stwebvanuatu@xxxxxxxxxxxx>
- To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
- Date: Fri, 20 Jul 2012 07:06:56 -0700 (PDT)
Here are some examples. The input data is a direct cut-and-paste from the
colprof output. I have calculated delta E with Gaurav Sharma's spreadsheet and
Bruce Lindblooms web calculator:
http://www.ece.rochester.edu/~gsharma/ciede2000/
http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE2000.html
[5.790875] 0.018533 0.060767 0.188920 -> 16.184140 24.186926 -63.268069 should
be 19.349371 22.206153 -58.841773
DE00 spreadsheet = 2.4096
DE00 Lindbloom = 2.4096
DE76 Lindbloom = 5.7909
[1.906550] 0.863110 0.849700 0.848230 -> 94.689681 -0.383334 0.713823 should be
96.521931 -0.897156 0.596434
DE00 spreadsheet = 1.3233
DE00 Lindbloom = 1.3233
DE76 Lindbloom = 1.9066
[3.648782] 0.114370 0.224380 0.096200 -> 54.928708 -42.874429 37.209866 should
be 52.027751 -44.149537 39.018775
DE00 spreadsheet = 2.8834
DE00 Lindbloom = 2.883450
DE76 Lindbloom = 3.648781
[4.530066] 0.286760 0.036334 0.022012 -> 38.996835 61.855796 36.960859 should
be 36.036227 64.919159 38.501022
DE00 spreadsheet = 2.6417
DE00 Lindbloom = 2.6417
DE76 Lindbloom = 3.063
[5.273161] 0.651050 0.422930 0.106950 -> 79.796759 4.157840 84.383180 should be
80.569480 3.851387 89.590407
DE00 spreadsheet = 1.2209
DE00 Lindbloom = 1.2209
DE76 Lindbloom = 5.2732
[3.185483] 0.357800 0.131360 0.220400 -> 48.673987 54.123752 -12.755375 should
be 48.059068 55.331845 -15.638028
DE00 spreadsheet = 1.3801
DE00 Lindbloom = 1.3801
DE76 Lindbloom = 3.1855
[3.829559] 0.071679 0.252420 0.368150 -> 49.812685 -30.674000 -32.260727 should
be 47.791690 -33.193813 -30.203630
DE00 spreadsheet = 2.5854
DE00 Lindbloom = 2.5854
DE76 Lindbloom = 3.8296
[2.015927] 0.023399 0.024048 0.024181 -> 17.588819 -0.942403 -0.176957 should
be 15.938875 -0.417952 -1.209720
DE00 spreadsheet = 1.6780
DE00 Lindbloom = 1.6780
DE76 Lindbloom = 2.0159
[11.990115] 0.407720 0.321030 0.050649 -> 70.288554 -10.231232 101.435263
should be 72.415918 -9.806180 89.643040
DE00 spreadsheet = 2.7719
DE00 Lindbloom = 2.7719
DE76 Lindbloom = 11.9901
I must have not noticed before that the delta E reported by colprof (flag -y)
exactly matches DE76. Anyone can easily verify this with their own data and
calculation of delta E for just one patch will do. Graeme has also confirmed
that colprof returns DE76 (Euclidean distance).
The next question's are:
Is DE76 used only for reporting errors or is it used in colprof for model
fitting as well?
Which delta E function is most appropriate for profiling (my application is
graphic arts)? Note there's a huge difference between DE76 = 11.99 and DE00 =
2.77 for the last patch in the above examples.
Stephen.
________________________________
From: Graeme Gill <graeme@xxxxxxxxxxxxx>
To: argyllcms@xxxxxxxxxxxxx
Sent: Thursday, 19 July 2012 11:53 PM
Subject: [argyllcms] Re: How is delta E calculated in colprof?
Stephen T wrote:
> Both of the above are consistent but colprof's delta E values are different
> and do not match
> DE76 and DE94 either.
Hi,
do you have a specific example ?
> Which delta E is colprof reporting? The documentation states only that "a
> summary of the average
> and maximum Lab delta E's will be printed out if this flag [-y] is set".
There is no qualification, so this is plain delta E (ie. Euclidean distance).
It's
open source, so you can always look at the source code...
> Is colprof applying any weighting to the DE00 calculation: KL, KC, KH not
> equal to 1.0?
Again, it's open source - it's easy enough to check, and it's noted in the
source that the equations are taken from:
"The CIEDE2000 Color-Difference Formula: Implementation Notes,
Supplementary Test Data, and Mathematical Observations", by
Gaurav Sharma, Wencheng Wu and Edul N. Dalal,
Color Res. Appl., vol. 30, no. 1, pp. 21-30, Feb. 2005.
Graeme Gill.
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