WLED/wled00/colors.cpp

#include "wled.h"

/*
 * Color conversion & utility methods
 */

/*
 * color blend function
 */
uint32_t IRAM_ATTR color_blend(uint32_t color1, uint32_t color2, uint16_t blend, bool b16) {
  if(blend == 0)   return color1;
  uint16_t blendmax = b16 ? 0xFFFF : 0xFF;
  if(blend == blendmax) return color2;
  uint8_t shift = b16 ? 16 : 8;

  uint32_t w1 = W(color1);
  uint32_t r1 = R(color1);
  uint32_t g1 = G(color1);
  uint32_t b1 = B(color1);

  uint32_t w2 = W(color2);
  uint32_t r2 = R(color2);
  uint32_t g2 = G(color2);
  uint32_t b2 = B(color2);

  uint32_t w3 = ((w2 * blend) + (w1 * (blendmax - blend))) >> shift;
  uint32_t r3 = ((r2 * blend) + (r1 * (blendmax - blend))) >> shift;
  uint32_t g3 = ((g2 * blend) + (g1 * (blendmax - blend))) >> shift;
  uint32_t b3 = ((b2 * blend) + (b1 * (blendmax - blend))) >> shift;

  return RGBW32(r3, g3, b3, w3);
}

/*
 * color add function that preserves ratio
 * idea: https://github.com/Aircoookie/WLED/pull/2465 by https://github.com/Proto-molecule
 */
uint32_t color_add(uint32_t c1, uint32_t c2)
{
  uint32_t r = R(c1) + R(c2);
  uint32_t g = G(c1) + G(c2);
  uint32_t b = B(c1) + B(c2);
  uint32_t w = W(c1) + W(c2);
  uint16_t max = r;
  if (g > max) max = g;
  if (b > max) max = b;
  if (w > max) max = w;
  if (max < 256) return RGBW32(r, g, b, w);
  else           return RGBW32(r * 255 / max, g * 255 / max, b * 255 / max, w * 255 / max);
}

void setRandomColor(byte* rgb)
{
  lastRandomIndex = strip.get_random_wheel_index(lastRandomIndex);
  colorHStoRGB(lastRandomIndex*256,255,rgb);
}

void colorHStoRGB(uint16_t hue, byte sat, byte* rgb) //hue, sat to rgb
{
  float h = ((float)hue)/65535.0;
  float s = ((float)sat)/255.0;
  byte i = floor(h*6);
  float f = h * 6-i;
  float p = 255 * (1-s);
  float q = 255 * (1-f*s);
  float t = 255 * (1-(1-f)*s);
  switch (i%6) {
    case 0: rgb[0]=255,rgb[1]=t,rgb[2]=p;break;
    case 1: rgb[0]=q,rgb[1]=255,rgb[2]=p;break;
    case 2: rgb[0]=p,rgb[1]=255,rgb[2]=t;break;
    case 3: rgb[0]=p,rgb[1]=q,rgb[2]=255;break;
    case 4: rgb[0]=t,rgb[1]=p,rgb[2]=255;break;
    case 5: rgb[0]=255,rgb[1]=p,rgb[2]=q;
  }
}

//get RGB values from color temperature in K (https://tannerhelland.com/2012/09/18/convert-temperature-rgb-algorithm-code.html)
void colorKtoRGB(uint16_t kelvin, byte* rgb) //white spectrum to rgb, calc
{
  float r = 0, g = 0, b = 0;
  float temp = kelvin / 100;
  if (temp <= 66) {
    r = 255;
    g = round(99.4708025861 * log(temp) - 161.1195681661);
    if (temp <= 19) {
      b = 0;
    } else {
      b = round(138.5177312231 * log((temp - 10)) - 305.0447927307);
    }
  } else {
    r = round(329.698727446 * pow((temp - 60), -0.1332047592));
    g = round(288.1221695283 * pow((temp - 60), -0.0755148492));
    b = 255;
  } 
  //g += 12; //mod by Aircoookie, a bit less accurate but visibly less pinkish
  rgb[0] = (uint8_t) constrain(r, 0, 255);
  rgb[1] = (uint8_t) constrain(g, 0, 255);
  rgb[2] = (uint8_t) constrain(b, 0, 255);
  rgb[3] = 0;
}

void colorCTtoRGB(uint16_t mired, byte* rgb) //white spectrum to rgb, bins
{
  //this is only an approximation using WS2812B with gamma correction enabled
  if (mired > 475) {
    rgb[0]=255;rgb[1]=199;rgb[2]=92;//500
  } else if (mired > 425) {
    rgb[0]=255;rgb[1]=213;rgb[2]=118;//450
  } else if (mired > 375) {
    rgb[0]=255;rgb[1]=216;rgb[2]=118;//400
  } else if (mired > 325) {
    rgb[0]=255;rgb[1]=234;rgb[2]=140;//350
  } else if (mired > 275) {
    rgb[0]=255;rgb[1]=243;rgb[2]=160;//300
  } else if (mired > 225) {
    rgb[0]=250;rgb[1]=255;rgb[2]=188;//250
  } else if (mired > 175) {
    rgb[0]=247;rgb[1]=255;rgb[2]=215;//200
  } else {
    rgb[0]=237;rgb[1]=255;rgb[2]=239;//150
  }
}

#ifndef WLED_DISABLE_HUESYNC
void colorXYtoRGB(float x, float y, byte* rgb) //coordinates to rgb (https://www.developers.meethue.com/documentation/color-conversions-rgb-xy)
{
  float z = 1.0f - x - y;
  float X = (1.0f / y) * x;
  float Z = (1.0f / y) * z;
  float r = (int)255*(X * 1.656492f - 0.354851f - Z * 0.255038f);
  float g = (int)255*(-X * 0.707196f + 1.655397f + Z * 0.036152f);
  float b = (int)255*(X * 0.051713f - 0.121364f + Z * 1.011530f);
  if (r > b && r > g && r > 1.0f) {
    // red is too big
    g = g / r;
    b = b / r;
    r = 1.0f;
  } else if (g > b && g > r && g > 1.0f) {
    // green is too big
    r = r / g;
    b = b / g;
    g = 1.0f;
  } else if (b > r && b > g && b > 1.0f) {
    // blue is too big
    r = r / b;
    g = g / b;
    b = 1.0f;
  }
  // Apply gamma correction
  r = r <= 0.0031308f ? 12.92f * r : (1.0f + 0.055f) * pow(r, (1.0f / 2.4f)) - 0.055f;
  g = g <= 0.0031308f ? 12.92f * g : (1.0f + 0.055f) * pow(g, (1.0f / 2.4f)) - 0.055f;
  b = b <= 0.0031308f ? 12.92f * b : (1.0f + 0.055f) * pow(b, (1.0f / 2.4f)) - 0.055f;

  if (r > b && r > g) {
    // red is biggest
    if (r > 1.0f) {
      g = g / r;
      b = b / r;
      r = 1.0f;
    }
  } else if (g > b && g > r) {
    // green is biggest
    if (g > 1.0f) {
      r = r / g;
      b = b / g;
      g = 1.0f;
    }
  } else if (b > r && b > g) {
    // blue is biggest
    if (b > 1.0f) {
      r = r / b;
      g = g / b;
      b = 1.0f;
    }
  }
  rgb[0] = 255.0*r;
  rgb[1] = 255.0*g;
  rgb[2] = 255.0*b;
}

void colorRGBtoXY(byte* rgb, float* xy) //rgb to coordinates (https://www.developers.meethue.com/documentation/color-conversions-rgb-xy)
{
  float X = rgb[0] * 0.664511f + rgb[1] * 0.154324f + rgb[2] * 0.162028f;
  float Y = rgb[0] * 0.283881f + rgb[1] * 0.668433f + rgb[2] * 0.047685f;
  float Z = rgb[0] * 0.000088f + rgb[1] * 0.072310f + rgb[2] * 0.986039f;
  xy[0] = X / (X + Y + Z);
  xy[1] = Y / (X + Y + Z);
}
#endif // WLED_DISABLE_HUESYNC

//RRGGBB / WWRRGGBB order for hex
void colorFromDecOrHexString(byte* rgb, char* in)
{
  if (in[0] == 0) return;
  char first = in[0];
  uint32_t c = 0;
  
  if (first == '#' || first == 'h' || first == 'H') //is HEX encoded
  {
    c = strtoul(in +1, NULL, 16);
  } else
  {
    c = strtoul(in, NULL, 10);
  }

  rgb[0] = R(c);
  rgb[1] = G(c);
  rgb[2] = B(c);
  rgb[3] = W(c);
}

//contrary to the colorFromDecOrHexString() function, this uses the more standard RRGGBB / RRGGBBWW order
bool colorFromHexString(byte* rgb, const char* in) {
  if (in == nullptr) return false;
  size_t inputSize = strnlen(in, 9);
  if (inputSize != 6 && inputSize != 8) return false;

  uint32_t c = strtoul(in, NULL, 16);

  if (inputSize == 6) {
    rgb[0] = (c >> 16);
    rgb[1] = (c >>  8);
    rgb[2] =  c       ;
  } else {
    rgb[0] = (c >> 24);
    rgb[1] = (c >> 16);
    rgb[2] = (c >>  8);
    rgb[3] =  c       ;
  }
  return true;
}

float minf (float v, float w)
{
  if (w > v) return v;
  return w;
}

float maxf (float v, float w)
{
  if (w > v) return w;
  return v;
}

/*
uint32_t colorRGBtoRGBW(uint32_t c)
{
  byte rgb[4];
  rgb[0] = R(c);
  rgb[1] = G(c);
  rgb[2] = B(c);
  rgb[3] = W(c);
  colorRGBtoRGBW(rgb);
  return RGBW32(rgb[0], rgb[1], rgb[2], rgb[3]);
}

void colorRGBtoRGBW(byte* rgb) //rgb to rgbw (http://codewelt.com/rgbw). (RGBW_MODE_LEGACY)
{
  float low = minf(rgb[0],minf(rgb[1],rgb[2]));
  float high = maxf(rgb[0],maxf(rgb[1],rgb[2]));
  if (high < 0.1f) return;
  float sat = 100.0f * ((high - low) / high);   // maximum saturation is 100  (corrected from 255)
  rgb[3] = (byte)((255.0f - sat) / 255.0f * (rgb[0] + rgb[1] + rgb[2]) / 3);
}
*/

byte correctionRGB[4] = {0,0,0,0};
uint16_t lastKelvin = 0;

// adjust RGB values based on color temperature in K (range [2800-10200]) (https://en.wikipedia.org/wiki/Color_balance)
uint32_t colorBalanceFromKelvin(uint16_t kelvin, uint32_t rgb)
{
  //remember so that slow colorKtoRGB() doesn't have to run for every setPixelColor()
  if (lastKelvin != kelvin) colorKtoRGB(kelvin, correctionRGB);  // convert Kelvin to RGB
  lastKelvin = kelvin;
  byte rgbw[4];
  rgbw[0] = ((uint16_t) correctionRGB[0] * R(rgb)) /255; // correct R
  rgbw[1] = ((uint16_t) correctionRGB[1] * G(rgb)) /255; // correct G
  rgbw[2] = ((uint16_t) correctionRGB[2] * B(rgb)) /255; // correct B
  rgbw[3] =                                W(rgb);
  return RGBW32(rgbw[0],rgbw[1],rgbw[2],rgbw[3]);
}

//approximates a Kelvin color temperature from an RGB color.
//this does no check for the "whiteness" of the color,
//so should be used combined with a saturation check (as done by auto-white)
//values from http://www.vendian.org/mncharity/dir3/blackbody/UnstableURLs/bbr_color.html (10deg)
//equation spreadsheet at https://bit.ly/30RkHaN
//accuracy +-50K from 1900K up to 8000K
//minimum returned: 1900K, maximum returned: 10091K (range of 8192)
uint16_t approximateKelvinFromRGB(uint32_t rgb) {
  //if not either red or blue is 255, color is dimmed. Scale up
  uint8_t r = R(rgb), b = B(rgb);
  if (r == b) return 6550; //red == blue at about 6600K (also can't go further if both R and B are 0)

  if (r > b) {
    //scale blue up as if red was at 255
    uint16_t scale = 0xFFFF / r; //get scale factor (range 257-65535)
    b = ((uint16_t)b * scale) >> 8;
    //For all temps K<6600 R is bigger than B (for full bri colors R=255)
    //-> Use 9 linear approximations for blackbody radiation blue values from 2000-6600K (blue is always 0 below 2000K)
    if (b < 33)  return 1900 + b       *6;
    if (b < 72)  return 2100 + (b-33)  *10;
    if (b < 101) return 2492 + (b-72)  *14;
    if (b < 132) return 2900 + (b-101) *16;
    if (b < 159) return 3398 + (b-132) *19;
    if (b < 186) return 3906 + (b-159) *22;
    if (b < 210) return 4500 + (b-186) *25;
    if (b < 230) return 5100 + (b-210) *30;
                 return 5700 + (b-230) *34;
  } else {
    //scale red up as if blue was at 255
    uint16_t scale = 0xFFFF / b; //get scale factor (range 257-65535)
    r = ((uint16_t)r * scale) >> 8;
    //For all temps K>6600 B is bigger than R (for full bri colors B=255)
    //-> Use 2 linear approximations for blackbody radiation red values from 6600-10091K (blue is always 0 below 2000K)
    if (r > 225) return 6600 + (254-r) *50;
    uint16_t k = 8080 + (225-r) *86;
    return (k > 10091) ? 10091 : k;
  }
}