It might be worth noting that your Grayscale equation is the Y value in the YIQ colorspace https://en.wikipedia.org/wiki/YIQ#From_RGB_to_YIQ https://en.wikipedi

It might be worth noting that your Grayscale equation is the Y value in the YIQ colorspace https://en.wikipedia.org/wiki/YIQ#From_RGB_to_YIQ https://en.wikipedia.org/wiki/YIQ#From_RGB_to_YIQ -- a technique similar to using the lightness value in EG HSL for picking a foreground or background color (similar to what the article does here: http://notes.neeasade.net/color-spaces.html#h-cb3c6479-7d62-4028-8942-2b033bb1247a http://notes.neeasade.net/color-spaces.html#h-cb3c6479-7d62-...). (I'm the author of the article)