move canvas colors code into its own file(s)

2 files changed, 228 insertions, 0 deletions

diff --git a/libs/canvas/canvas/colors.h b/libs/canvas/canvas/colors.h
new file mode 100644
index 0000000000..80d57c698f
--- /dev/null
+++ b/libs/canvas/canvas/colors.h
@@ -0,0 +1,35 @@
+/*
+    Copyright (C) 2011-2013 Paul Davis
+    Author: Carl Hetherington <cth@carlh.net>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <cairomm/context.h>
+
+#include "canvas/visibility.h"
+#include "canvas/types.h"
+
+namespace ArdourCanvas {
+
+	extern LIBCANVAS_API void color_to_hsv (Color color, double& h, double& s, double& v);
+	extern LIBCANVAS_API Color hsv_to_color (double h, double s, double v, double a);
+
+	extern LIBCANVAS_API void color_to_rgba (Color, double& r, double& g, double& b, double& a);
+	extern LIBCANVAS_API Color rgba_to_color (double r, double g, double b, double a);
+
+        uint32_t LIBCANVAS_API contrasting_text_color (uint32_t c);
+}
+
diff --git a/libs/canvas/colors.cc b/libs/canvas/colors.cc
new file mode 100644
index 0000000000..3c638935ec
--- /dev/null
+++ b/libs/canvas/colors.cc
@@ -0,0 +1,193 @@
+/*
+    Copyright (C) 2014 Paul Davis
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <algorithm>
+#include <cmath>
+#include <stdint.h>
+
+#include "canvas/colors.h"
+
+using namespace std;
+using namespace ArdourCanvas;
+
+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;
+}
+
+// Inverse of sRGB "gamma" function.
+static inline double 
+inv_gam_sRGB (double c) 
+{
+        if (c <= 0.04045) {
+                return c/12.92;
+        } else {
+                return pow(((c+0.055)/(1.055)),2.4);
+        }
+}
+
+// sRGB "gamma" function
+static inline int 
+gam_sRGB(double v) 
+{
+        if (v <= 0.0031308) {
+                v *= 12.92;
+        } else {
+                v = 1.055 * pow (v, 1.0 / 2.4) - 0.055;
+        }
+        return int (v*255+.5);
+}
+
+static double 
+luminance (uint32_t c)
+{
+        // sRGB luminance(Y) values
+        const double rY = 0.212655;
+        const double gY = 0.715158;
+        const double bY = 0.072187;
+
+        double r, g, b, a;
+
+        ArdourCanvas::color_to_rgba (c, r, g, b, a);
+        
+        return (gam_sRGB (rY*inv_gam_sRGB(r) + gY*inv_gam_sRGB(g) + bY*inv_gam_sRGB(b))) / 255.0;
+}    
+
+uint32_t
+ArdourCanvas::contrasting_text_color (uint32_t c)
+{
+        static const uint32_t white = ArdourCanvas::rgba_to_color (1.0, 1.0, 1.0, 1.0);
+        static const uint32_t black = ArdourCanvas::rgba_to_color (0.0, 0.0, 0.0, 1.0);
+
+	return (luminance (c) < 0.50) ? white : black;
+}