(Originally published in 2010)
I bet you've seen color pickers before. They are neat UI elements that allow you to select a particular color that you may have in mind. They do that by organizing the entire color space in a way that's easily browsed. Usually, pickers show you a 2D panel that displays all colors along two of the dimensions, and a slider for the third dimension; or they only show you a small-ish subset of all the colors.
I’m fascinated with color, especially when there’s math or technology involved. And so I set out to build a picker that displays all the colors, yet requires only a single two-dimensional surface.
To learn all the details of how I generated this new color picker, see this post. In short, however, the idea is this: we want to map a 3D space (0..255, 0..255, 0..255) into a 2D space (0..4095, 0..4095) in a smooth way, so we'll use space-filling curves. "Walking" the R, G and B dimensions, however, gives a pretty unsmooth picker, so instead I "walked" the color intensity, and for each intensity, "walked" over all possible colors of that intensity. I then picked the order in which the colors would appear by sorting by R, G and then B.
The resulting color picker has the interesting property that it displays all possible colors (up to the image's resolution) in a single image: