+using std::max;
+using std::min;
+
+void
+ArdourCanvas::color_to_hsv (Color color, double& h, double& s, double& v)
+{
+ double r, g, b, a;
+ double cmax;
+ double cmin;
+ double delta;
+
+ color_to_rgba (color, r, g, b, a);
+
+ if (r > g) {
+ cmax = max (r, b);
+ } else {
+ cmax = max (g, b);
+ }
+
+ if (r < g) {
+ cmin = min (r, b);
+ } else {
+ cmin = min (g, b);
+ }
+
+ v = cmax;
+
+ delta = cmax - cmin;
+
+ if (cmax == 0) {
+ // r = g = b == 0 ... v is undefined, s = 0
+ s = 0.0;
+ h = -1.0;
+ }
+
+ if (delta != 0.0) {
+ if (cmax == r) {
+ h = fmod ((g - b)/delta, 6.0);
+ } else if (cmax == g) {
+ h = ((b - r)/delta) + 2;
+ } else {
+ h = ((r - g)/delta) + 4;
+ }
+
+ h *= 60.0;
+ }
+
+ if (delta == 0 || cmax == 0) {
+ s = 0;
+ } else {
+ s = delta / cmax;
+ }
+
+}
+
+ArdourCanvas::Color
+ArdourCanvas::hsv_to_color (double h, double s, double v, double a)
+{
+ s = min (1.0, max (0.0, s));
+ v = min (1.0, max (0.0, v));
+
+ if (s == 0) {
+ // achromatic (grey)
+ return rgba_to_color (v, v, v, a);
+ }
+
+ h = min (360.0, max (0.0, h));
+
+ double c = v * s;
+ double x = c * (1.0 - fabs(fmod(h / 60.0, 2) - 1.0));
+ double m = v - c;
+
+ if (h >= 0.0 && h < 60.0) {
+ return rgba_to_color (c + m, x + m, m, a);
+ } else if (h >= 60.0 && h < 120.0) {
+ return rgba_to_color (x + m, c + m, m, a);
+ } else if (h >= 120.0 && h < 180.0) {
+ return rgba_to_color (m, c + m, x + m, a);
+ } else if (h >= 180.0 && h < 240.0) {
+ return rgba_to_color (m, x + m, c + m, a);
+ } else if (h >= 240.0 && h < 300.0) {
+ return rgba_to_color (x + m, m, c + m, a);
+ } else if (h >= 300.0 && h < 360.0) {
+ return rgba_to_color (c + m, m, x + m, a);
+ }
+ return rgba_to_color (m, m, m, a);
+}
+
+void
+ArdourCanvas::color_to_rgba (Color color, double& r, double& g, double& b, double& a)
+{
+ r = ((color >> 24) & 0xff) / 255.0;
+ g = ((color >> 16) & 0xff) / 255.0;
+ b = ((color >> 8) & 0xff) / 255.0;
+ a = ((color >> 0) & 0xff) / 255.0;
+}
+
+ArdourCanvas::Color
+ArdourCanvas::rgba_to_color (double r, double g, double b, double a)
+{
+ /* clamp to [0 .. 1] range */
+
+ r = min (1.0, max (0.0, r));
+ g = min (1.0, max (0.0, g));
+ b = min (1.0, max (0.0, b));
+ a = min (1.0, max (0.0, a));
+
+ /* convert to [0..255] range */
+
+ unsigned int rc, gc, bc, ac;
+ rc = rint (r * 255.0);
+ gc = rint (g * 255.0);
+ bc = rint (b * 255.0);
+ ac = rint (a * 255.0);
+
+ /* build-an-integer */
+
+ return (rc << 24) | (gc << 16) | (bc << 8) | ac;
+}
+