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[vrtris] / src / color.c

diff --git a/src/color.c b/src/color.c
new file mode 100644 (file)
index 0000000..f1de5f4
--- /dev/null
+++ b/src/color.c
@@ -0,0 +1,85 @@
+#include <math.h>
+#include "color.h"
+
+static float min3(float a, float b, float c)
+{
+       if(a < b && a < c) return a;
+       return b < c ? b : c;
+}
+
+static float max3(float a, float b, float c)
+{
+       if(a > b && a > c) return a;
+       return b > c ? b : c;
+}
+
+void rgb_to_hsv(float r, float g, float b, float *h, float *s, float *v)
+{
+       float min, max, delta;
+
+       min = min3(r, g, b);
+       max = max3(r, g, b);
+       *v = max;
+
+       delta = max - min;
+
+       if(max != 0) {
+               *s = delta / max;
+       } else {
+               *s = 0;
+               *h = -1;
+               return;
+       }
+
+       if(!delta) delta = 1.0f;
+
+       if(r == max)
+               *h = (g - b) / delta;
+       else if( g == max )
+               *h = 2 + (b - r) / delta;
+       else
+               *h = 4 + (r - g) / delta;
+
+       *h *= 60;
+       if(*h < 0) {
+               *h += 360.0f;
+       }
+       *h /= 360.0f;
+}
+
+#define RETRGB(red, green, blue) \
+       do { \
+               *r = (red); \
+               *g = (green); \
+               *b = (blue); \
+               return; \
+       } while(0)
+
+void hsv_to_rgb(float h, float s, float v, float *r, float *g, float *b)
+{
+       float sec, frac, o, p, q;
+       int hidx;
+
+       if(s == 0.0f) {
+               *r = *g = *b = v;
+               return;
+       }
+
+       sec = floor(h * (360.0f / 60.0f));
+       frac = (h * (360.0f / 60.0f)) - sec;
+
+       o = v * (1.0f - s);
+       p = v * (1.0f - s * frac);
+       q = v * (1.0f - s * (1.0f - frac));
+
+       hidx = (int)sec;
+       switch(hidx) {
+       default:
+       case 0: RETRGB(v, q, o);
+       case 1: RETRGB(p, v, o);
+       case 2: RETRGB(o, v, q);
+       case 3: RETRGB(o, p, v);
+       case 4: RETRGB(q, o, v);
+       case 5: RETRGB(v, o, p);
+       }
+}