Reenigne blog

For various visualization programming tasks, it’s useful to have a set of colours that are as far apart as possible. I set out to write a program to generate such sets.

The first problem is that we must work in a perceptual colour space such as Lab rather than the usual sRGB, or our colours will be overly concentrated in the areas where sRGB over-represents.

Next, I set up a system of mutually repelling particles and let them arrange themselves (sliding along the sides and edges as required). This didn’t work too well even just in sRGB space – the trouble is that I don’t care about minimizing the distance to the most distant colours, only the nearest ones. I thought about do a Delaunay triangulation to find the nearest neighbours of each point, but it turns out that’s overkill – all you need to do is just repel the 6 nearest particles (and recalculate what those particles are after each frame). If you end up with the closest points all on one side, the particle will be repelled away until one of the closest points is on the other side.

Even with this fix, I was still getting strange results. After some head-scratching, I realized that it was just to the “kinks” in the some of the edges of the sRGB gamut in Lab space:

The particles tend get “stuck” in these kinks.

I’m not quite sure what to do about this. Perhaps I can find optimal sets in a rectilinear gamut and then gradually morph this into sRGB while continuing to let the particles repel.

Inspired by this XKCD comic:

I made this:

And this, going in the opposite direction:

Here is a concept that I feel that there ought to be words for but which there don’t seem to be.

Suppose we arrange the spectrum of colours into the familiar colour wheel:

What is the word that corresponds to “clockwise” on this diagram (and “anticlockwise” on the mirror image of this diagram)? I.e. the word that means “more blue than red”, “more green than blue” and “more red than green” simultaneously? What is the word for the opposite hue angle direction?

Bonus points for the best neologisms for these equal and opposite concepts.

I’m reading a great book at the moment, Dave Gorman’s Googlewhack adventure. This book chronicles the epic procrastination techniques Dave Gorman used to avoid starting to write a novel. The novel he was going to write was about a guy who sees a brand new colour in a dream and travels the world searching for an example of it.

Sounds pretty far fetched, no? Well, quite by accident I came across this page in which a physicist Andrew Hamilton comes up with an entirely new colour.

In case you’re put off by the maths on that page, here’s a basic explanation. The human eye contains 3 types of colour receptors (call them red, green and blue for the sake of argument). When we see a particular colour, these receptors are triggered in some ratio – the ratio determines the hue of the colour you are looking at. The red receptors detect long wavelengths, the blue receptors detect short wavelengths and the green receptors detect wavelengths in between. However, even when looking at even the purest green light the red and/or blue receptors are triggered to some extent because their ranges of sensitivity all overlap.

So what would you see if you could trigger just the green receptors? It would be a colour that no-one had ever seen before, since light with this colour isn’t physically possible. Hamilton hypothesizes that this colour (which he calls “psychedelic aquamarine”) would be the colour you got if you took the colour of the water around the reefs of Heron Island in the Great Barrier Reef of Australia and subtracted white to make the colour even more saturated:

In this picture, psychedelic aquamarine would be to the bottom left image as the top right image is to the top left image. When I tried to apply the same transformation the bottom left image that I applied to the top left image to get the top right image, nothing happened (which is hardly surprising since obviously my computer is not capable of displaying psychedelic aquamarine).

According to Hamilton, people who are red/green colour-blind see psychadelic aquamarine all the time, whenever they look at something which us non-colour-blind people would see as red. Such a colour would stimulate the green receptors, but not the blue receptors (as it’s too red) nor the red receptors (since these don’t exist in such people). However, since we can only describe colours by mentioning things which are that colour, a colour-blind person’s description of psychendelic aquamarine would probably sound very much like a colour-seeing person’s description of the colour red.

I wonder if it would be possible to make a machine that would allow people to see this colour. It would have to work by scanning someone’s retinas, identifying where the green receptors are and firing out photons in such directions that they only hit the green receptors. If someone built such a machine and stared into it, would they just see a very vivid (bluish) green or would they have the incredible experience of seeing a brand new colour that they would never have seen before?