Update: See the follow-up post here.
Aldo Cortesi posted a link today to allrgb.com, a site dedicated to images visualizing the RGB colour space - in particular, 4096x4096 images that use each RGB value exactly once. Inspired by his hilbert curve visualization and the urge to spend a day programming, I present to you: the all-RGB Mandelbrot set.
Sort by colour...My idea was this: instead of trying to visualize the colour space directly, why not use a base image for the "shape", and then map the RGB spectrum onto it? I thought that if I could find an image with an even spread of colours, this would let me make each pixel unique yet keep the overall look untouched.
To perform this mapping, I chose to define an ordering based on the 3 dimensional Hilbert curve. Cortesi explains it far better than I can, but the basic idea is this: the Hilbert curve can be used to find an ordering of all 16.8 million colours so that if you were to stretch them out on a line, every colour would be there and they would flow smoothly from one to another. Like this, except a lot smoother and a lot longer.
Choosing an imageWhen I started this morning, I had the idea that the output images would look reasonably close to the source images. I was half right; the images certainly have all the same features as before, but the colouring is all wrong. In hindsight the reason is obvious - unless the original had a perfectly even spectrum of colours, the mapping would be stretched in some places and shifted in others, and in general not line up nicely.
While interesting, this wasn't exactly what I was going for. Hmm...what image could I use where it wouldn't matter if the colours were all shifted? The first thing that came to mind was a visualization like the Mandelbrot set, where the colours are arbitrarily chosen anyways. A quick Google search found me this:
Which, when transformed, came out as this: