I have managed to find code to convert RGB to XY. Can't make it work the other way around.
I have looked through Philips Hue SDK https://github.com/johnciech/PhilipsHueSDK/blob/master/ApplicationDesignNotes/RGB%20to%20xy%20Color%20conversion.md
I have found this javascript code: Philips hue, convert xy from api to HEX or RGB and converted it to c# but it doesn't work as expected. I think my math is not strong enough.. please advise.
public class PhilipsHueRgbObject
{
public int Red { get; set; }
public int Green { get; set; }
public int Blue { get; set; }
}
public static PhilipsHueRgbObject xyBriToRgb(double x, double y, double bri)
{
double z = 1.0d - x - y;
double Y = bri / 255.0d; // Brightness of lamp
double X = (Y / y) * x;
double Z = (Y / y) * z;
double r = X * 1.612d - Y * 0.203d - Z * 0.302d;
double g = -X * 0.509d + Y * 1.412d + Z * 0.066d;
double b = X * 0.026d - Y * 0.072d + Z * 0.962d;
r = (r <= 0.0031308d ? 12.92d * r : (1.0d + 0.055d) * Math.Pow(r, (1.0d / 2.4d)) - 0.055d);
g = (g <= 0.0031308d ? 12.92d * g : (1.0d + 0.055d) * Math.Pow(g, (1.0d / 2.4d)) - 0.055d);
b = (b <= 0.0031308d ? 12.92d * b : (1.0d + 0.055d) * Math.Pow(b, (1.0d / 2.4d)) - 0.055d);
double maxValue = Math.Max(r, Math.Max(g, b));
r /= maxValue;
g /= maxValue;
b /= maxValue;
r = r * 255;
if (r < 0)
{
r = 255;
}
g = g * 255;
if (g < 0)
{
g = 255;
}
b = b * 255;
if (b < 0)
{
b = 255;
}
return new PhilipsHueRgbObject()
{
Red = (int)r,
Green = (int)g,
Blue = (int)b
};
}
public static string groupRBG(string ipAddress, string userName, int groupNumber, int red, int green, int blue)
{
try
{
float redArg = (red > 0.04045f) ? (float) Math.Pow((red + 0.055f)/(1.0f + 0.055f), 2.4f) : (red/12.92f);
// Convert RGB to Hue
float greenArg = (green > 0.04045f)
? (float) Math.Pow((green + 0.055f)/(1.0f + 0.055f), 2.4f)
: (green/12.92f);
float blueArg = (blue > 0.04045f)
? (float) Math.Pow((blue + 0.055f)/(1.0f + 0.055f), 2.4f)
: (blue/12.92f);
float X = redArg*0.664511f + greenArg*0.154324f + blueArg*0.162028f;
float Y = redArg*0.283881f + greenArg*0.668433f + blueArg*0.047685f;
float Z = redArg*0.000088f + greenArg*0.072310f + blueArg*0.986039f;
float x = X/(X + Y + Z);
float y = Y/(X + Y + Z);
return
httpRequest(
@"http://" + ipAddress + @"/api/" + userName + @"/groups/" + groupNumber.ToString() +
@"/action/", @"{" + "\"on\": true,\"xy\": [" + x.ToString() + "," + y.ToString() + "]" + @"}");
}
catch (Exception ex)
{
ErrorLog.Error("Error : {0}", ex.Message);
return null;
}
}
function xyBriToRgb(x, y, bri){
z = 1.0 - x - y;
Y = bri / 255.0; // Brightness of lamp
X = (Y / y) * x;
Z = (Y / y) * z;
r = X * 1.612 - Y * 0.203 - Z * 0.302;
g = -X * 0.509 + Y * 1.412 + Z * 0.066;
b = X * 0.026 - Y * 0.072 + Z * 0.962;
r = r <= 0.0031308 ? 12.92 * r : (1.0 + 0.055) * Math.pow(r, (1.0 / 2.4)) - 0.055;
g = g <= 0.0031308 ? 12.92 * g : (1.0 + 0.055) * Math.pow(g, (1.0 / 2.4)) - 0.055;
b = b <= 0.0031308 ? 12.92 * b : (1.0 + 0.055) * Math.pow(b, (1.0 / 2.4)) - 0.055;
maxValue = Math.max(r,g,b);
r /= maxValue;
g /= maxValue;
b /= maxValue;
r = r * 255; if (r < 0) { r = 255 };
g = g * 255; if (g < 0) { g = 255 };
b = b * 255; if (b < 0) { b = 255 };
return {
r :r,
g :g,
b :b
}
}
I expect to see exact same values coming back for the group. http:// --HueBridgeIP --/api/ -- UserString --/groups
