0.1.2 add RGB565 16 bit

Kelvin2RGB.cpp

@@ -1,14 +1,22 @@
 //
 //    FILE: Kelvin2RGB.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
+// VERSION: 0.1.2
 //    DATE: 2018-01-31
 // PURPOSE: Arduino library for converting temperature to RGB values
 //     URL: https://github.com/RobTillaart/Kelvin2RGB
 
+//  HISTORY
+//  0.1.0    2018-01-31  initial version
+//  0.1.1    2020-12-30  ??
+//  0.1.2    2021-06-01  add RGB565() - 16 bit color - output
+
+
 #include "Kelvin2RGB.h"
 
-#define DIVIDE_255  0.0039215686274509803921568627451
+
+#define DIVIDE_255      (0.0039215686274509803921568627451)
+
 
 Kelvin2RGB::Kelvin2RGB()
 {
@@ -19,6 +27,7 @@ Kelvin2RGB::Kelvin2RGB()
   _blue  = 0;
 }
 
+
 void Kelvin2RGB::begin()
 {
 }
@@ -30,7 +39,7 @@ void Kelvin2RGB::convert_TH(float temperature, float brightness)
   _temperature = constrain(temperature, 0, 65500);
   _brightness = constrain(brightness, 0, 100);
 
-  _red = _green = _blue = 0;
+  _red = _green = _blue = 0;  
   float t = _temperature * 0.01;
 
   if (t <= 66)
@@ -49,16 +58,8 @@ void Kelvin2RGB::convert_TH(float temperature, float brightness)
     _green = 288.1221695283 * pow(t - 60, -0.0755148492);
     _blue  = 255;
   }
-  float f = 0.01 * _brightness;
-  _red   = constrain(f * _red,   0, 255);
-  _green = constrain(f * _green, 0, 255);
-  _blue  = constrain(f * _blue,  0, 255);
-  _rgb   = round(_red) * 65536UL + round(_green) * 256UL + round(_blue);
-
-  // divide by 255 to get factors between 0..1
-  _red   *=  DIVIDE_255;
-  _green *=  DIVIDE_255;
-  _blue  *=  DIVIDE_255;
+
+  _normalize();
 }
 
 
@@ -92,10 +93,35 @@ void Kelvin2RGB::convert_NB(float temperature, float brightness)
     _blue = 255;
   }
 
+  _normalize();
+}
+
+
+// 16 bit color
+uint16_t Kelvin2RGB::RGB565()
+{
+  uint16_t val = 0;
+  val  = uint8_t(_red * 32);
+  val <<= 6;
+  val |= uint8_t(_green * 64);
+  val <<= 5;
+  val |= uint8_t(_blue * 32);
+  return val; 
+}
+
+
+/////////////////////////////////////////////////////////////
+//
+// private
+//
+void Kelvin2RGB::_normalize()
+{
   float f = 0.01 * _brightness;
+
   _red   = constrain(f * _red,   0, 255);
   _green = constrain(f * _green, 0, 255);
   _blue  = constrain(f * _blue,  0, 255);
+
   _rgb   = round(_red) * 65536UL + round(_green) * 256UL + round(_blue);
 
   // divide by 255 to get factors between 0..1
@@ -104,4 +130,5 @@ void Kelvin2RGB::convert_NB(float temperature, float brightness)
   _blue  *=  DIVIDE_255;
 }
 
+
 // -- END OF FILE --

Kelvin2RGB.h

@@ -2,54 +2,24 @@
 //
 //    FILE: Kelvin2RGB.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.1
+// VERSION: 0.1.2
 //    DATE: 2018-01-31
 // PURPOSE: Arduino library for converting temperature to RGB values
 //     URL: https://github.com/RobTillaart/Kelvin2RGB
 //
-// Based upon article Tanner Helland  and Neil Bartlett
-// http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
-// http://www.zombieprototypes.com/?p=210  
-// https://en.wikipedia.org/wiki/Color_temperature#Categorizing_different_lighting
 
-#define KELVIN2RGB_LIB_VERSION "0.1.1"
 
-#include "Arduino.h"
+#define KELVIN2RGB_LIB_VERSION        (F("0.1.2"))
 
-// based on https://en.wikipedia.org/wiki/Color_temperature#Categorizing_different_lighting
-// TODO a memory efficient storage -> uint8_t 17 .. 255 (factor 100)
-//      how? hash function? parameter settings  convert(dayLightSetting)
-// enum DLS ?
+#include "Arduino.h"
 
-/*
-    NAME              TEMPERATURE
-    =============================
-    dark            = 0;
-    match           = 1700;
-    sodiumLamp      = 1700;
-    candleFlame     = 1850;
-    sunrise         = 1850;
-    sunset          = 1850;
-    bulb            = 2400;
-    bulbSoftWhite   = 2550;
-    LEDlamp         = 2700;
-    warmWhite       = 3000;
-    studioLight     = 3200;
-    studioCPlight   = 3350;
-    daylightHorizon = 5000;
-    flashLight      = 5700;
-    xenonLight      = 6200;
-    dayLightBright  = 6500;
-    normal          = 6500;
-    screenlow       = 6500;
-    screenMed       = 8000;
-    screenHigh      = 9500;
-    polewardSky0    = 15000;
-    polewardSky1    = 19000;
-    polewardSky2    = 23000;
-    polewardSky3    = 27000;
-*/
 
+//
+// Based upon article Tanner Helland  and Neil Bartlett
+// http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
+// http://www.zombieprototypes.com/?p=210  
+// https://en.wikipedia.org/wiki/Color_temperature#Categorizing_different_lighting
+//
 //
 // based on https://en.wikipedia.org/wiki/Color_temperature#Categorizing_different_lighting
 //
@@ -86,21 +56,26 @@ class Kelvin2RGB
 {
 public:
   Kelvin2RGB();
-  void begin();
+  void begin();         // empty function - obsolete?
 
   // temp = 0..65500   brightness = 0.0 .. 100.0%
   void convert_TH(float temperature, float brightness = 100);
   void convert_NB(float temperature, float brightness = 100);
 
   float    temperature() { return _temperature; };
   float    brightness()  { return _brightness;  };
-  inline float red()     { return _red;   };
-  inline float green()   { return _green; };
-  inline float blue()    { return _blue;  };
-  uint32_t RGB()         { return _rgb; }
 
-
+  // returns 0.0 .. 1.0
+  float    red()         { return _red;   };
+  float    green()       { return _green; };
+  float    blue()        { return _blue;  };
+
+  uint32_t RGB()         { return _rgb; };   // 32 bit color
+  uint16_t RGB565();                         // 16 bit color
+
 private:
+  void  _normalize();
+
   float    _temperature;
   float    _brightness;
   float    _red;

README.md

@@ -6,7 +6,8 @@
 
 # Kelvin2RGB
 
-Arduino library for converting temperature to RGB values
+Arduino library for converting temperature and brightness to RGB values
+
 
 ## Credentials
 
@@ -17,19 +18,21 @@ http://www.zombieprototypes.com/?p=210
 https://en.wikipedia.org/wiki/Color_temperature#Categorizing_different_lighting
 
 There are more approximation formulas, some claim to be better, 
-however these are not investigated.
+however these are not investigated. On request these can be added.
+
 
 ## Description
 
 The library converts a temperature in Kelvin and a brightness (0..100%) 
  to 3 numbers red, green and blue.
 These numbers are weights can be used to correct a colorimage for virtual white temperature.
 
-There are 2 convert functions where the **convert_NB()** is claimed to be the 
-more accurate one.
+There are 2 convert functions where the **convert_NB()** is claimed to be 
+the more accurate one.
+
+With the numbers R,G,B calculated one can convert images so they will look
+more like taken with candle light, sunrise or sunset etc. 
 
-With the numbers R,G,B calculated one can convert images so they will look more like 
-taken with candle light, sunrise or sunset etc. 
 
 **pseudo code**
 ```cpp
@@ -75,11 +78,20 @@ note this is different from Helland / Bartlett who both use an integer value 0 .
 - **float blue()** returns blue channel weight 0.0 .. 1.0
 - **uint32_t RGB()** retuns a 24 bit RGB value,  
 more efficient than 3 floats for communication. 
+- **uint16_t RGB565()** retuns a 16 bit RGB value, 
+5 bits for R 6 for green and 5 for blue. 
+
 
-## future
+## Future
 
 - separate brightness per color channel to mimic "artificial illumination"
 - define constants like candleLight as parameter.
+- investigate other formulas.
+- investigate usability for RGB ledstrip.
+- remove begin() ?
+- add reset() ?
+- add BGR() ?
+- add CMYK() ?
 
 
 ## Operations

examples/Kelvin2RGB565_diff_hex/Kelvin2RGB565_diff_hex.ino

@@ -0,0 +1,48 @@
+//
+//    FILE: Kelvin2RGB565_diff_hex.ino
+//  AUTHOR: Rob Tillaart
+// VERSION: 0.1.2
+// PURPOSE: demo - shows difference between 2 convert functions for the 565 16 bit coding
+//    DATE: 2021-06-01
+//     URL: https://github.com/RobTillaart/Kelvin2RGB
+//
+
+// shows difference between the two calculations
+//       best viewed in plotter.
+
+#include "Kelvin2RGB.h"
+
+Kelvin2RGB KRGB;
+Kelvin2RGB KRGB2;
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+
+  KRGB.begin();
+  KRGB2.begin();
+
+  test_difference();
+}
+
+void loop()
+{
+}
+
+void test_difference()
+{
+  float bright = 100.0;
+  for (uint32_t temp = 0; temp < 70000; temp += 200)
+  {
+    KRGB.convert_TH(temp, bright);
+    KRGB2.convert_NB(temp, bright);
+
+    Serial.print(KRGB.RGB565(), HEX);
+    Serial.print("\t");
+    Serial.print(KRGB2.RGB565(), HEX);
+    Serial.print("\n");
+  }
+}
+
+// -- END OF FILE --

examples/Kelvin2RGB_diff_hex/Kelvin2RGB_diff_hex.ino

@@ -0,0 +1,48 @@
+//
+//    FILE: Kelvin2RGB_diff_hex.ino
+//  AUTHOR: Rob Tillaart
+// VERSION: 0.1.2
+// PURPOSE: demo - shows difference between 2 convert functions for the 565 16 bit coding
+//    DATE: 2021-06-01
+//     URL: https://github.com/RobTillaart/Kelvin2RGB
+//
+
+// shows difference between the two calculations
+//       best viewed in plotter.
+
+#include "Kelvin2RGB.h"
+
+Kelvin2RGB KRGB;
+Kelvin2RGB KRGB2;
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+
+  KRGB.begin();
+  KRGB2.begin();
+
+  test_difference();
+}
+
+void loop()
+{
+}
+
+void test_difference()
+{
+  float bright = 100.0;
+  for (uint32_t temp = 0; temp < 70000; temp += 200)
+  {
+    KRGB.convert_TH(temp, bright);
+    KRGB2.convert_NB(temp, bright);
+
+    Serial.print(KRGB.RGB(), HEX);
+    Serial.print("\t");
+    Serial.print(KRGB2.RGB(), HEX);
+    Serial.print("\n");
+  }
+}
+
+// -- END OF FILE --

keywords.txt

@@ -12,6 +12,7 @@ red	KEYWORD2
 green	KEYWORD2
 blue	KEYWORD2
 RGB	KEYWORD2
+RGB565	KEYWORD2
 
 # Constants (LITERAL1)
 

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/Kelvin2RGB.git"
   },
-  "version": "0.1.1",
+  "version": "0.1.2",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*"

library.properties

@@ -1,5 +1,5 @@
 name=Kelvin2RGB
-version=0.1.1
+version=0.1.2
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for converting temperature to RGB values