colour

Since my last visit to this subject I have been thinking about how to represent a collection of random colors so that it looks sorted and that no information is lost during that process. I quickly realised that I needed to use all three aspects of the color space, which lends itself to generating 3D objects. Indeed, the red, green, blue color space is built around a cube so it can often be represented as a cube.

The hue, saturation, and value color space is built around the concept of a cylinder, which means that 2 of the axis lend themselves to a circumference of a circle (the hue) and the diameter of a circle (the saturation). This is an example of the polar coordinate system. We can therefore draw a circle using hue and saturation and the value can be used to represent a different aspect of the color space.

Sorting colors is the sort of thing that you never really think about until you need to do it. Sorting a bunch of items by their color is useful in a number of applications, but the simplest is just to display items to the user in a more controlled manner. As it happens sorting with colors is a much more complex topic than I originally thought and required digging into quite a bit more maths than I expected.

Incidentally, there is a whole world of color maths that I didn't know existed until I started looking into this. It was worth learning about though.

Setting Up

To start with, I created a little Color class so that I could have a standard way of storing a color. This just takes the red, green and blue values for a color and allows a simple way of accessing those values.

Here is a short bit of code to generate a random hexadecimal colour using PHP. Essentially you just create a random number between 0 (000000) and 10,000,000 (ffffff) and turn this into a hexadecimal number using the PHP function dechex.