Skip to content

Instantly share code, notes, and snippets.

@EDais

EDais/colourTemperature.js

Created August 30, 2017 14:50
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save EDais/1ba1be0fe04eca66bbd588a6c9cbd666 to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save EDais/1ba1be0fe04eca66bbd588a6c9cbd666 to your computer and use it in GitHub Desktop.
Download ZIP

Revisions

  1. EDais created this gist Aug 30, 2017.
    27 changes: 27 additions & 0 deletions colourTemperature.js
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,27 @@
    "use strict";

    const clamp = (num, min, max) => num < min ? min : num > max ? max : num;

    /** Given a temperature (in Kelvin), estimate an RGB equivalent
    * @param {number} tmpKelvin - Temperature (in Kelvin) between 1000 and 40000
    * @returns {{r:number, g:number, b:number}} - RGB channel intensities (0-255)
    * @description Ported from: http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
    */
    exports.getRGBFromTemperature = function(tmpKelvin) {
    // All calculations require tmpKelvin \ 100, so only do the conversion once
    tmpKelvin = clamp(tmpKelvin, 1000, 40000) / 100;

    // Note: The R-squared values for each approximation follow each calculation
    return {
    r: tmpKelvin <= 66 ? 255 :
    clamp(329.698727446 * (Math.pow(tmpKelvin - 60, -0.1332047592)), 0, 255), // .988

    g: tmpKelvin <= 66 ?
    clamp(99.4708025861 * Math.log(tmpKelvin) - 161.1195681661, 0, 255) : // .996
    clamp(288.1221695283 * (Math.pow(tmpKelvin - 60, -0.0755148492)), 0, 255), // .987

    b: tmpKelvin >= 66 ? 255 :
    tmpKelvin <= 19 ? 0 :
    clamp(138.5177312231 * Math.log(tmpKelvin - 10) - 305.0447927307, 0, 255) // .998
    };
    };