node-red-contrib-chroma

A Node-RED node for color conversions This node mostly is based on chroma.js with additional formats like RGBW and CIExyz

chroma.js is a small-ish zero-dependency JavaScript library (13.5kB) for all kinds of color conversions and color scales

features

• conversion between various color formats
• conversion between array format (chroma.js default) and objects
• scaling of relative values either as 0..1 or 0..100
• support of floating point and integer values
• chroma.js api accessible to
  • manipulate colors
  • generate color scales

latest updates

0.0.3

• fix: return callback function
• updated examples
• various minor fixes and typos

Install

Either use the Editor - Menu - Manage Palette - Install option, or run the following command in your Node-RED user directory (typically ~/.node-red) after installing Node-RED-dashboard.

npm i node-red-contrib-chroma

Examples

Examples can be imported via import/examples in the top right menu of the editor

1. conversions test of all (except alpha channel) available formats
2. mix use of chroma
3. interactive scale use of chroma scales using the api (with a dashboard slider as input and a button to show the resulting color)

inputs

msg.payload

Alpha channel is supported to most color formats.

For relative values select the format 0..1 or 0..100 to be expected.

chroma.js input formats

• Hex string: "#ff0000"
• RGB string: "rgb(255, 0, 0)"
• RGB object: {r: 255, g: 0, b: 0}
• HSL string: "hsl(360, 50%, 100%)"
• HSL object: {h: 360, s: 50, l: 100}
• HSV object: {h: 360, s: 100, v: 50}
• HSI object: {h: 360, s: 100, i: 50}
• LAB object: {l: 1, a: 1, b: 1}
• LCH object: {l: 1, c: 1, h: 1}
• named colors: string
• temperature: number 1000..40,000 k
• luminance: number 0..1

additional formats

• RGBW object {r:255, g:255, b:255, w:255} *useful for RGBW LEDs
• CIExyz object {x:1, y:1, z:1} for home automation like zigbee

Node: CIExy can't be used as input as it can't be converted clearly to RGB (or somebody can to show me how)

msg.api

the api can be accessed by sending an arrayof objects

The first example of the chroma.js api documentation:

chroma.scale(['#fafa6e','#2A4858']).mode('lch').colors(6)

translates to

[
    { "scale": ["#fafa6e","#2A4858"] },
    { "mode": "lch" },
    { "colors": 6 }
]

This example will generate a six colors scale form yellow to dark green

If the api call returns a function msg.payload will be used as it's parameter. Subsequent messages (without msg.api) will return the result of the returned callback function

If no msg.payload is sent the callback function is send to the output (to be tested further).

output

All supported input formats can be selected as output. In addition CIExy can be selected

All chroma.js multi value results are formatted as an array. Tick the option to get the result as an object

For relative values select the format 0..1 or 0..100 to be emitted.

Numerical values can be rounded integers or returned as float values