YAML Color Definitions

Introduction

Defining a color sequence in code is tedious. Definining more sequences even more so. Our package depends on color definitions coming from a YAML file.

This page describes the structure of such a file.

Specification

One or more color definitions are located in a YAML file, defining color sequences used in your program.

YAML structure

The base YAML structure is as follows:

meta:
    release: "0.5.0.0"
wheels:
    - wheel:
        name: "white"
        colors:
            - rgb: [255, 255, 255]
    - wheel:
        name: "RGB"
        colors:
            - rgb: [255, 0, 0]
            - rgb: [0, 255, 0]
            - rgb: [0, 0, 255]
    ...

The structure contains 2 segments:

• meta - containing metadata about the file, version (for compatibility reasons) and similar. In the current release, this section is ignored.

• wheels - a list of different (named) colorwheels. Each colorwheel item is defined within a wheel section.

Wheel Definitions

Wheels can be represented in several ways, depending on the color effect we want to achieve. Generally, we have 2 types of wheel elements: listed, or calculated.

For example:

...
- wheel:
    name: "long-rainbow"
    type: "rainbow"
    size: 64
    amplitude: 127
    center: 128
    frequency: 0.3
- wheel:
    name: "RGB"
    type: "sequence" # default value, need not be specified
    colors:
        - rgb: [255, 0, 0]
        - rgb: [0, 255, 0]
        - rgb: [0, 0, 255]
...

Above, we can see a standard RGB sequence, plus a ‘calculated’ sequence from parameters. The differentiator is the type field. This field identifies what to do with parameters, and defaults to sequence.

If you load the above definition into Colorwheels (using the ColorwheelsConfig load_wheels method), there will be 2 named color wheels you can switch back and forth.

Wheel types

sequence

Sequence is the basic type of a wheel, and if not specified, this type becomes the default value. A ‘sequence’ contains a ‘colors’ list, where every list item is defined by it’s RGB elements.

Below a usage example:

...
- wheel:
    name: "RGB"
    type: "sequence" # default value, need not be specified
    colors:
        - rgb: [255, 0, 0]
        - rgb: [0, 255, 0]
        - rgb: [0, 0, 255]
...

rainbow

Rainbow is a generated wheel. You specify how many elements to use, plus some algorithm parameters. You can generate rainbow sequences without really looking into the detail of the implementation: just specify ‘size’ (i.e. number of colors) and leave the rest to defaults.

Below a rainbow wheel:

...
- wheel:
    name: "my-rainbow"
    type: "rainbow"
    size: 32        # default value, need not be specified
    amplitude: 127  # default value, need not be specified
    center: 128     # default value, need not be specified
    frequency: 0.3  # default value, need not be specified
...