change rendering technique for waveforms, add back optional gradient, add back amplitude scaling, add rgb/hsv conversion utilities to canvas

libs/canvas/utils.cc

@@ -17,10 +17,132 @@
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
+#include <algorithm>
+#include <cmath>
 #include <stdint.h>
 #include <cairomm/context.h>
 #include "canvas/utils.h"
 
+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;
+}
+
 void
 ArdourCanvas::set_source_rgba (Cairo::RefPtr<Cairo::Context> context, Color color)
 {