Add color conversion from RGB to XY.

Bounds to closest representable color of the gamut.

Add color conversion from RGB to XY.
Bounds to closest representable color of the gamut.
Jojo-1000 · Moritz Wirger
1 parent aec7baeb
Showing 4 changed files with 142 additions and 11 deletions
include/hueplusplus/Units.h
src/CMakeLists.txt
src/SimpleColorHueStrategy.cpp
src/Units.cpp
@@ -27,7 +27,6 @@
 namespace hueplusplus
 {
-
 struct HueSaturation
 {
     int hue;
@@ -40,11 +39,30 @@ struct XY
     float y;
 };
+struct XYBrightness
+{
+    XY xy;
+    float brightness;
+};
+
+struct ColorGamut
+{
+    XY redCorner;
+    XY greenCorner;
+    XY blueCorner;
+
+    XY corrected(const XY& xy) const;
+};
+
 struct RGB
 {
     uint8_t r;
     uint8_t g;
     uint8_t b;
+
+    XYBrightness toXY() const;
+    XYBrightness toXY(const ColorGamut& gamut) const;
+    static RGB fromXY(const XYBrightness& xy);
 };
 } // namespace hueplusplus
@@ -16,8 +16,9 @@ set(hueplusplus_SOURCES
     SimpleColorTemperatureStrategy.cpp
     StateTransaction.cpp
     TimePattern.cpp
+    Units.cpp
     UPnP.cpp
-    Utils.cpp)
+    Utils.cpp )
 # on windows we want to compile the WinHttpHandler
 if(WIN32)
@@ -287,14 +287,5 @@ std::pair&lt;float, float&gt; SimpleColorHueStrategy::getColorXY(const HueLight&amp; light
 {
     return std::make_pair(light.state.getValue()["state"]["xy"][0].get<float>(), light.state.getValue()["state"]["xy"][1].get<float>());
 }
-/*bool SimpleColorHueStrategy::pointInTriangle(float pointx, float pointy, float
-x0, float y0, float x1, float y1, float x2, float y2)
-{
-float A = (-y1 * x2 + y0*(-x1 + x2) + x0*(y1 - y2) + x1 * y1);
-int8_t sign = A < 0 ? -1 : 1;
-float s = (y0 * x2 - x0 * y2 + (y2 - y0) * pointx + (x0 - x2) * pointy) * sign;
-float t = (x0 * y1 - y0 * x1 + (y0 - y1) * pointx + (x1 - x0) * pointy) * sign;
-return s > 0 && t > 0 && (s + t) < A * sign;
-}*/
 } // namespace hueplusplus
+#include <cmath>
+
+#include <hueplusplus/Units.h>
+
+namespace hueplusplus
+{
+namespace
+{
+float sign(const XY& p0, const XY& p1, const XY& p2)
+{
+    return (p0.x - p2.x) * (p1.y - p2.y) - (p1.x - p2.x) * (p0.y - p2.y);
+}
+
+bool isInTriangle(const XY& xy, const ColorGamut& triangle)
+{
+    const float d1 = sign(xy, triangle.redCorner, triangle.greenCorner);
+    const float d2 = sign(xy, triangle.greenCorner, triangle.blueCorner);
+    const float d3 = sign(xy, triangle.blueCorner, triangle.redCorner);
+
+    const bool hasNeg = (d1 < 0) || (d2 < 0) || (d3 < 0);
+    const bool hasPos = (d1 > 0) || (d2 > 0) || (d3 > 0);
+    return !(hasNeg && hasPos);
+}
+
+bool isRightOf(const XY& xy, const XY& p1, const XY& p2)
+{
+    return sign(xy, p1, p2) < 0;
+}
+
+XY projectOntoLine(const XY& xy, const XY& p1, const XY& p2)
+{
+    // Using dot product to project onto line
+    // Vector AB = B - A
+    // Vector AX = X - A
+    // Projected length l = (AX dot AB) / len(AB)
+    // Result: E = A + l*AB/len(AB) = A + AB * (AX dot AB) / (len(AB))^2
+
+    const float abX = p2.x - p1.x;
+    const float abY = p2.y - p1.y;
+    const float lenABSquared = abX * abX + abY * abY;
+
+    const float dot = (xy.x - p1.x) * abX + (xy.y - p1.y) * abY;
+    const float eX = p1.x + abX * dot / lenABSquared;
+    const float eY = p1.y + abY * dot / lenABSquared;
+    return XY {eX, eY};
+}
+} // namespace
+
+XY ColorGamut::corrected(const XY& xy) const
+{
+    // red, green and blue are in counterclockwise orientation
+    if (isRightOf(xy, redCorner, greenCorner))
+    {
+        // Outside of triangle, check whether to use nearest corner or point on line
+        if (isRightOf(xy, greenCorner, blueCorner))
+        {
+            // Point is outside of red-green line, closest to green corner
+            return greenCorner;
+        }
+        else if (isRightOf(xy, blueCorner, redCorner))
+        {
+            // Point is outside of red-green line, closest to red corner
+            return redCorner;
+        }
+        else
+        {
+            // Point is closest to line, project onto it
+            return projectOntoLine(xy, redCorner, greenCorner);
+        }
+    }
+    else if (isRightOf(xy, greenCorner, blueCorner))
+    {
+        // Green corner already checked above
+        if (isRightOf(xy, blueCorner, redCorner))
+        {
+            // Point is outside of green-blue line, closest to blue corner
+            return blueCorner;
+        }
+        else
+        {
+            return projectOntoLine(xy, greenCorner, blueCorner);
+        }
+    }
+    else if (isRightOf(xy, blueCorner, redCorner))
+    {
+        // All corners already checked
+        return projectOntoLine(xy, blueCorner, redCorner);
+    }
+    return xy;
+}
+
+XYBrightness RGB::toXY() const
+{
+    const float red = r / 255.f;
+    const float green = g / 255.f;
+    const float blue = b / 255.f;
+
+    const float redCorrected = (red > 0.04045f) ? pow((red + 0.055f) / (1.0f + 0.055f), 2.4f) : (red / 12.92f);
+    const float greenCorrected = (green > 0.04045f) ? pow((green + 0.055f) / (1.0f + 0.055f), 2.4f) : (green / 12.92f);
+    const float blueCorrected = (blue > 0.04045f) ? pow((blue + 0.055f) / (1.0f + 0.055f), 2.4f) : (blue / 12.92f);
+
+    const float X = redCorrected * 0.664511f + greenCorrected * 0.154324f + blueCorrected * 0.162028f;
+    const float Y = redCorrected * 0.283881f + greenCorrected * 0.668433f + blueCorrected * 0.047685f;
+    const float Z = redCorrected * 0.000088f + greenCorrected * 0.072310f + blueCorrected * 0.986039f;
+
+    const float x = X / (X + Y + Z);
+    const float y = Y / (X + Y + Z);
+    return XYBrightness {XY {x, y}, Y};
+}
+
+XYBrightness RGB::toXY(const ColorGamut& gamut) const
+{
+    XYBrightness xy = toXY();
+    xy.xy = gamut.corrected(xy.xy);
+
+    return xy;
+}
+
+RGB RGB::fromXY(const XYBrightness& xy) {}
+
+} // namespace hueplusplus
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