Distil: a colour palette generator

WIP - Not ready for production use

Distil is a Rust library that creates a colour palette from the most frequently used colours in an image.

| Examples | How does it work? | 1.0 checklist |

How does it work?

Lets go through it step by step.

Downsampling

Distil starts by scaling the image down—whilst preserving its aspect ratio—until it consists of no more that 1000 pixels.

Quantization

From there, it's run through the NeuQuant algorithm to reduce it to an 8-bit image composed of 256 colours.

Colour differentiation

Next, the number of appearances each unique colour makes in the image is counted and put into a Vec. That Vec is then sorted by most frequently used colour to least frequently used. Lets name it palette for the sake of clarity going forward.

A separate Vec, which we'll dub refined_palette, is now created and it's from that Vec that the final palette will be built.

Starting from the top (i.e. the most frequently used colour), the program then works its way down palette comparing how similar x — the current colour from palette being processed — is by human eye standards to each and every colour in refined_palette.

If there are no colours similar to x already in refined_palette, then x gets added to refined_palette. If, however, there is a similar colour already in refined_palette then an average is made of the two colours which takes into account their frequency in the image.

The difference between two colours from the human eye perspective is calculated with the CIEDE2000 colour difference algorithm.

Colour weight

With all of the colours now processed, the colours in the refined_palette Vec are once again sorted from most frequently used to least frequently used. An important note here though is that the sorting is done taking into account the occurrence count of each of the pixels that were deemed similar in colour and merged together when building refined_palette.

1.0 checklist

• Handle a pure-white or pure-black image being processed. Pixels that are too dark or too light to be interesting in a palette currently get filtered out during quantization.
• Add a way to create a distillation from multiple Distils. i.e. A way to get one Distil from the colours of multiple images.

Examples