Reveal and document MakeColorHSB

These "secret" functions are very useful and shouldn't be kept hidden.  Let's start documenting them.

drawing.cpp

@@ -311,12 +311,6 @@ void SaveImage(unsigned int suffix)
 //
 
 
-// Creates a color using a (hue, saturation, value) triple instead of (red, green, blue).
-//
-// - S and V are in the usual [0, 256) range, but H is in degrees: [0, 360)
-//
-Color MakeColorHSV(int h, int s, int v);
-
 // If your program is going to be writing every pixel every frame, this is a simple optimization
 // over issuing Width*Height calls to DrawPixel.  Instead of spending time on the thread-safety
 // overhead Width*Height times, the entire operation is performed in bulk behind a single lock.
@@ -391,12 +385,12 @@ Color MakeColor(int r, int g, int b, int a)
 
 constexpr Color MakeColor(int r, int g, int b)
 {
-    return (0xFF << 24) | ((r & 0xFF) << 16) | ((g & 0xFF) << 8) | ((b & 0xFF) << 0);
+    return 0xFF000000 | ((r & 0xFF) << 16) | ((g & 0xFF) << 8) | ((b & 0xFF) << 0);
 }
 
-Color MakeColorHSV(int hue, int sat, int val)
+Color MakeColorHSB(int hue, int sat, int val)
 {
-    float h = fmod(hue / 360.0f, 1.0f);
+    float h = min(1.0f, max(0.0f, (hue % 360) / 360.0f));
     float s = min(1.0f, max(0.0f, sat / 255.0f));
     float v = min(1.0f, max(0.0f, val / 255.0f));
 

drawing.h

@@ -90,6 +90,22 @@ static const Color LightMagenta = MakeColor(255,  85, 255);
 static const Color Yellow =       MakeColor(255, 255,  85);
 static const Color White =        MakeColor(255, 255, 255);
 
+// MakeColorHSB is like MakeColor but instead of using red, green, and blue
+// values, you get to specify the hue.  This is ideal for making rainbows!
+//
+// hue is an angle (in degrees) between 0 and 360.
+// (0 is red, 30 is orange, 60 is yellow, 240 is blue...)
+//
+// saturation and brightness should be between 0 and 255.
+// 
+// saturation=0 makes everything grayscale.
+// saturation=255 will be the most vivid version of that color.
+//
+// brightness=0 is always black.
+// brightness=255 is the brightest version of that color.
+//
+Color MakeColorHSB(int hue, int saturation, int brightness);
+
 
 
 

example8_smoke.cpp

@@ -163,7 +163,6 @@ void velocityStep(vector<float> &u, vector<float> &v, vector<float> &u0, vector<
 
 
 // Secret functions from drawing.cpp!
-Color MakeColorHSV(int h, int s, int v);
 void Present(const vector<Color> &screen);
 void DrawString(int x, int y, const string &s, const Color c, bool centered, function<void(int x, int y, Color c)> customDraw);
 
@@ -177,11 +176,11 @@ Color FluidColor(float u, float v, float density, bool showVelocity)
     {
         int h = min(360, max(0, int(sqrt(u*u + v*v) * 1500.0)));
         int v = min(255, max(0, int(density * 500.0)));
-        return MakeColorHSV(h, 255, v);
+        return MakeColorHSB(h, 255, v);
     }
 
     const int value = min(360, max(0, int(density * 100.0f)));
-    return MakeColorHSV(max(0, value - 310), value / 2, value);
+    return MakeColorHSB(max(0, value - 310), value / 2, value);
 }
 
 // Returns a list of points between the given coordinates