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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 :class:`Colorwheels` (using the :class:`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
...