Complementary color definition

[mediatechnologic]

I have a question or a suggestion for Rickrack. I am using v2.9.10 on Win10pro x64.

It is about the "real" complementary colors. Called also "after image" optical colors. With this possible but important definition the complementary color of color A is the color B, which results in the linear sum of both colors A+B under the condition, that the result of this addition is a non-color gray value.

Here is an example: The complementary color to this yellow with sRGB = (199,167,000) is this blue with sRGB = (131,171,231). The calculation can be done by using the nonlinear transfer function of sRGB to convert to linear RGB values. The addition with correct perceived brightness (luminance) has to result in a gray value with R=G=B and then the colors are complementary. In this case the luminance of both colors is L = 39.7 %.

Please find attached a screenshot from Rickrack with the mentioned color values. The complementary color for the yellow circle is NOT directly opposite, but more to the center and a little bit shifted towards cyan.

Please find attached my related figure added on top of a publication graphic from MacAdam https://sites.socsci.uci.edu/~kjameson/macadam1938b.pdf Of course this correct calculation does also mean, that for some colors there do not exist complementary colors. Not only for sRGB, but also for other color spaces including the complete horse shoe shape of CIE.