dE(2000)
dE(2000)
- Subject: dE(2000)
- From: Steve Kale <email@hidden>
- Date: Sun, 25 Nov 2007 21:38:35 +0000
- Thread-topic: dE(2000)
Hi
Thanks. I actually found this before I got this digest. Turns out I had
misunderstood Bruce's annotation for the inverse tangents (whatever they
are) and had the coordinates around the wrong way. The spreadsheet you
referenced below helped me find the error. I have not been through their
paper in detail but noticed the mention of "minor discontinuities". What's
the sense out there as to 2000 vs 1974 dE? My assumption is that while
still not perfect, 2000 is still an improvement on 1974.
Regards
Steve
> From: <email@hidden>
> Reply-To: <email@hidden>
> Date: Sun, 25 Nov 2007 12:02:27 -0800 (PST)
> To: <email@hidden>
> Subject: Colorsync-users Digest, Vol 4, Issue 424
>
>
>
> From: Graeme Gill <email@hidden>
> Reply-To: <email@hidden>
> Date: Sun, 25 Nov 2007 13:29:54 +1100
> Cc: ColorSync Users Mailing List <email@hidden>
> Subject: Re: xyZ to LAB and dE (2000)
>
> Steve Kale wrote:
>> I¹m also getting errors in my dE calculations albeit I can¹t for the life of
>> me find the error. I¹m comparing target SMPTE-C Rec601 R, G, B, C, M, Y and
>> white values with measures from a calibrated display. My dE for R, G, M, Y
>> and White are very, very close but not exactly those generated by Bruce¹s
>> colour difference calculator but Blue and Cyan are way off. It¹s
>> frustrating because I¹ve been over the formulae a dozen times. Any ideas?
>
> What I've found is that the example spreadsheets created by the
> originators of such standards, are sometimes a bit loose on their
> accuracy compared with (say) implementing the same calculations with
> doubles in C. de2000 has some extra issues as well. These
> are mentioned in the following paper:
>
> "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.
>
> If you google the title, it's downloadable from Gaurav Sharma's website.
>
> I did an implementation in icclib in the Argyll source code.
> It's in argyll/icc/icclib.c and the function is called "icmCIE2Ksq",
> and the test harness testDE2K.c is also included in the source.
>
> Graeme Gill.
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