1 files changed, 59 insertions, 0 deletions
diff --git a/src/hsv2rgb.c b/src/hsv2rgb.c
new file mode 100644
index 0000000..9f445e9
--- /dev/null
+++ b/src/hsv2rgb.c
@@ -0,0 +1,59 @@
+/* hsv2rgb.c
+ * Convert Hue Saturation Value to Red Green Blue
+ *
+ * P.J. 08-Aug-98
+ *
+ * Reference:
+ * D. F. Rogers
+ * Procedural Elements for Computer Graphics
+ * McGraw Hill 1985
+ */
+
+#include "hsv2rgb.h"
+ 
+int hsv2rgb( struct hsv_colour *hsv, struct rgb_colour *rgb ) {
+   /*
+    * Purpose:
+    * Convert HSV values to RGB values
+    * All values are in the range [0.0 .. 1.0]
+    */
+   float S, H, V, F, M, N, K;
+   int   I;
+   
+   S = hsv->s;  /* Saturation */
+   H = hsv->h;  /* Hue */
+   V = hsv->v;  /* value or brightness */
+   
+   if ( S == 0.0 ) {
+      /* 
+       * Achromatic case, set level of grey 
+       */
+      rgb->r = V;
+      rgb->g = V;
+      rgb->b = V;
+   } else {
+      /* 
+       * Determine levels of primary colours. 
+       */
+      if (H >= 1.0) {
+         H = 0.0;
+      } else {
+         H = H * 6;
+      } /* end if */
+      I = (int) H;   /* should be in the range 0..5 */
+      F = H - I;     /* fractional part */
+
+      M = V * (1 - S);
+      N = V * (1 - S * F);
+      K = V * (1 - S * (1 - F));
+
+      if (I == 0) { rgb->r = V; rgb->g = K; rgb->b = M; }
+      if (I == 1) { rgb->r = N; rgb->g = V; rgb->b = M; }
+      if (I == 2) { rgb->r = M; rgb->g = V; rgb->b = K; }
+      if (I == 3) { rgb->r = M; rgb->g = N; rgb->b = V; }
+      if (I == 4) { rgb->r = K; rgb->g = M; rgb->b = V; }
+      if (I == 5) { rgb->r = V; rgb->g = M; rgb->b = N; }
+   } /* end if */
+
+   return 0;
+} /* end function hsv2rgb */