ESPHOME custom light that provides color temperature support to RGBW lights. This differs from the original (see link in the code) by mapping the RGBW from the

ColorTempRGBWLight.h

#include "esphome.h"

// Constants
const float maxMired = 500;
const float minMired = 153;
const float scale1 = 1.25f;
const float red_offset = 0.4f;
const float green_offset = 0.8f;

/**
 * Map a RGBW Light into a tunable color / RGB Light 
 * 
 * Bruce McDonald, Frank Evers (I think)
 *
 * derived from:
 * https://gist.github.com/madjam002/31cc88640efa370630fed6914fa4eb7f
 */
class ColorTempRGBWLight : public Component, public LightOutput {
public:

  ColorTempRGBWLight(
    FloatOutput *red, 
    FloatOutput *green,  
    FloatOutput *blue, 
    FloatOutput *white
  ) {
    red_ = red;
    green_ = green;
    blue_ = blue;
    white_ = white;
    
    // Create initial state
    colorTemp_ = -1.0f;
    brightness_ = -1.0f;
    rgbChanged_ = false;
    
    // default scaling
    cr = 1;
    br = 0;
    cg = 0.6;
    bg = 0;
    cb = -1.5;
    bb = 0.5;
    cw = -0.7;
    bw = 1;
  }
 
  /**
   * Constructor with scaling provided.
   */
  ColorTempRGBWLight(
    FloatOutput *red, 
    FloatOutput *green,  
    FloatOutput *blue, 
    FloatOutput *white,
    float _br,
    float _cr,
    float _bg,
    float _cg,
    float _bb,
    float _cb,
    float _bw,
    float _cw
  ) {
    red_ = red;
    green_ = green;
    blue_ = blue;
    white_ = white;
    
    // Create initial state
    colorTemp_ = -1.0f;
    brightness_ = -1.0f;
    rgbChanged_ = false;
    
    // Configured scaling
    cr = _cr;
    br = _br;
    cg = _cg;
    bg = _bg;
    cb = _cb;
    bb = _bb;
    cw = _cw;
    bw = _bw;
  }

  /** 
   * Get the traits for this light 
   */
  LightTraits get_traits() override {
    auto traits = LightTraits();
    
    traits.set_supports_brightness(true);
    traits.set_supports_rgb(true);
    traits.set_supports_rgb_white_value(false);
    traits.set_supports_color_temperature(true);
    traits.set_min_mireds(minMired); // home assistant minimum 153
    traits.set_max_mireds(maxMired); // home assistant maximum 500

    return traits;
  }

  /**
   * Write the state to this light
   */
  void write_state(LightState *state) override {
    float colorTemp, brightness;
    state->current_values_as_brightness(&brightness);
    colorTemp = state->current_values.get_color_temperature();

    // If the color temp changed or the color temp is unchanged but the brightness is changed then process that.
    if(colorTemp != colorTemp_ || (!rgbChanged_ && brightness != brightness_)) {
        // Normalize the colorTemp
        float xaxis = (colorTemp - minMired) / (maxMired - minMired);  // Varies from 0 to 1 as it moves from MIN to MAX
    
        // Place the rgb values on three lines
        float red = std::min(std::max((cr * xaxis + br) * brightness,0.0f), 1.0f);
        float green = std::min(std::max((cg * xaxis + bg) * brightness,0.0f), 1.0f);
        float blue = std::min(std::max((cb * xaxis + bb) * brightness,0.0f), 1.0f);
        float white = std::min(std::max((cw * xaxis + bw) * brightness,0.0f), 1.0f);

        this->red_->set_level(red);
        this->green_->set_level(green);
        this->blue_->set_level(blue);
        this->white_->set_level(white);
        
//        ESP_LOGD("custom",
//            "Outputs:  Xaxis: %f, Red %f, Green %f Blue %f White %f",
//            xaxis, xaxis * brightness, xaxis/2.5f * brightness, std::max(-xaxis * 2 + 2, 0.0f) * brightness,  (-xaxis * 0.6 + 1) * brightness);
        // Store this
        colorTemp_ = colorTemp;
        rgbChanged_ = false;
    } else {
        float red, green, blue, cwhite, wwhite;
        state->current_values_as_rgbww(&red, &green, &blue, &cwhite, &wwhite);

        this->red_->set_level(red);
        this->green_->set_level(green);
        this->blue_->set_level(blue);
        this->white_->set_level(0);
        
        // remember a color change
        rgbChanged_ = true;
    }
    
    brightness_ = brightness; 
  }


protected:
  FloatOutput *red_;
  FloatOutput *green_;
  FloatOutput *blue_;
  FloatOutput *white_;
  
  float colorTemp_;
  float brightness_;
  
  bool rgbChanged_;
  
  // red intercept and scale
  float br;
  float cr;
  
  // green intercept and scale
  float bg;
  float cg;
  
  // blue intercept and scale
  float bb;
  float cb;
  
  // white intercept and scale
  float bw;
  float cw;
};

The original author is Jamie Greeff - https://gist.github.com/madjam002

Thanks for this! I added another check around setting RGB values -- one of my automations would turn off the White channel when the light was already on and set to white.

https://gist.github.com/vandarin/5782958e9eca16b3caf4c7742e8d9d24

Is there any reason why this hasn't been submitted as a PR for ESPHome?

Go for it.

…

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