Add MacAdam ellipses plotting example.

[KelSolaar]

References

• Macadam, D. L. (1942). Visual Sensitivities to Color Differences in Daylight. Journal of the Optical Society of America, 32(5), 247. doi:10.1364/JOSA.32.000247
• https://sites.google.com/site/malscolourscience/macadam

[iinnovations]

What is the plan for this? I have not found a well-reasoned MacAdam ellipse interpolation example from the literature. Or is the plan here to simply allow plotting of the data as recorded? There are a number of adhocs available, e.g. the fluorescent lighting standard.

[KelSolaar]

I created the issue more to remember to take a look at it but I have no particular plan for it right now.

[iinnovations]

Thanks Thomas. Do ellipse and/or ANSI bin generators currently exist in colour? Tests for inclusion? I have this code elsewhere and would consider porting them.

On Nov 16, 2014, at 10:26 AM, Thomas Mansencal notifications@github.com wrote:

I created the issue more to remember to take a look at it but I have no particular plan for it right now.

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Reply to this email directly or view it on GitHub.

[KelSolaar]

Neither of those exists right now! That would be very nice if you were to implement support for them actually!

[nschloe]

I'm currently trying to get MacAdams ellipses plotted in colorio, but I'm somewhat at loss on how to interpret the data in the original paper. Table 3 therein gives the ellipse data, but when plotting the x-y locations of the filter pairs, their connecting lines, and the average theta settings, I'm getting all but a coherent image from which one can deduce an ellipse:

How does everyone draw those at all?

[KelSolaar]

I have never looked at that beyond saying would be great to have :)

[nschloe]

Got it:

Turns out that you have to use the delta y/delta x and delta s data (plus a curve fit) to reproduce the ellipses. I still have no idea how to correlate this with the actual measurements, but I guess that goes to show that you'll have to be very cautious when using MacAdam data for any quantitative studies.

[KelSolaar]

Nice! PR Welcome ;)

[iinnovations]

You’re going to have to parametrize these so that you can feed them into a geometry point in feature function anyway. I’ve done this in other languages and will run into this shortly here in python. I’ll send a PR when I get to it. C

…

On Feb 28, 2018, at 11:55 AM, Thomas Mansencal ***@***.***> wrote: Nice! PR Welcome ;) — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[KelSolaar]

Thanks Colin (@iinnovations)!

[KelSolaar]

Gave it a stab as I needed to plot them in another diagram than CIE 1931 while using ellipse canonical form coefficients. We have a few new definitions to deal with that now, conversion from canonical to general form coefficients, ellipse fitting using Halir and Flusser (1998) method and a few plotting definitions.

Closing this one!

[vvclin-git]

You can calculate MacAdam ellipse using FMC equations.
https://www.osapublishing.org/josa/abstract.cfm?uri=josa-61-1-118