Fix bug in hsv-rgb conversion

colours.c

@@ -1,6 +1,5 @@
 #include <SDL2/SDL.h>
 #include <stdbool.h>
-#include <time.h>
 
 SDL_Color get_random_color(unsigned int seed) {
     int red = rand_r(&seed) % 255;
@@ -39,7 +38,6 @@ bool m_equal(double a, double b) {
     return (a - b) * (a - b)  < 0.00001;
 }
 
-
 enum colour_space {
     CS_HSV,
     CS_HSL,
@@ -54,7 +52,9 @@ struct colour {
     enum colour_space sp;
 };
 
- // h = [0,360], s = [0,1], v = [0,1] //              if s == 0, then h = -1 (undefined)
+// https://en.wikipedia.org/wiki/HSL_and_HSV#From_RGB
+// h = [0,360], s = [0,1], v = [0,1] 
+// if s == 0, then h = -1 (undefined)
 struct colour get_hs_l_v(SDL_Color c, enum colour_space sp) {
     struct colour ret;
     memset(&ret, 0, sizeof(struct colour));
@@ -116,12 +116,13 @@ struct colour get_hsv(SDL_Color c) {
     return get_hs_l_v(c, CS_HSV); 
 }
 
-// https://en.wikipedia.org/wiki/HSI_color_space
 double magic_hsv_function(int n, struct colour c) {
-    double res =  c.v - c.v * c.s;
+    double res = 0;
     double k = fmod(n + (c.h / 60), 6);
     double arr[] = {k, 4 - k, 1};
-    res = res * m_max(arr, 3); 
+    double k_b = m_min(arr, 3);
+    double k_c = 0 > k_b ? 0 : k_b;
+    res = c.v - c.v * c.s * k_c; 
     return res;
 }
 
@@ -216,35 +217,23 @@ void test(int seed) {
     printf("\n");
 }
 
+void wheel() {
+    struct colour c;
+    c.s = 0.999;
+    c.v = 0.99;
+    c.l = 0.5;
+    c.sp = CS_HSV;
+    for(int i = 0; i < 360; i+=5) {
+        c.h = (double)i;
+        SDL_Color rgb = get_rgb(c);
+        /*printf("HSL: %f %f %f\n",c.h, c.s, c.l);*/
+        /*printf("RGB: %d %d %d\n",rgb.r,rgb.g,rgb.b);*/
+        print_colour(rgb);
+    }
+}
+
+
 int main() {
-    test(1231);
-    test(2131);
-    test(123);
-    test(121);
-    test(1802);
-}
-
-//"#d48d47
-//"#88934c
-//"#c88153
-//"#7c9f58
-//"#bc755f
-
-//"#c67c64
-//"#cc825e
-//"#ba6f70
-//"#d98e51
-//"#ad637d
-
-//"#221534
-//"#241336
-//"#1f1831
-//"#271423
-//"#1c1b2e
-
-//"#77f0a6
-//"#83fb9a
-//"#61dabc
-//"#0b128b
-//"#4ac3d3
+    wheel();
+}