use W3C color difference computation to select black or white text for region name...

diff --git a/gtk2_ardour/time_axis_view_item.cc b/gtk2_ardour/time_axis_view_item.cc
index d8d3cee8078e387486dd50bdd6ed8836e4317c2e..24a1c711ba36de5bfa66b18386413af3e0212b2d 100644 (file)
--- a/gtk2_ardour/time_axis_view_item.cc
+++ b/gtk2_ardour/time_axis_view_item.cc
@@ -728,6 +728,61 @@ TimeAxisViewItem::set_colors()
        if (name_highlight) {
                name_highlight->set_fill_color (fill_color);
        }
+
+       if (name_text) {
+               double r, g, b, a;
+
+               const double black_r = 0.0;
+               const double black_g = 0.0;
+               const double black_b = 0.0;
+
+               const double white_r = 1.0;
+               const double white_g = 1.0;
+               const double white_b = 1.0;
+
+               ArdourCanvas::color_to_rgba (fill_color, r, g, b, a);
+               
+               /* Use W3C contrast guideline calculation */
+
+               double white_contrast = (max (r, white_r) - min (r, white_r)) +
+                       (max (g, white_g) - min (g, white_g)) + 
+                       (max (b, white_b) - min (b, white_b));
+
+               double black_contrast = (max (r, black_r) - min (r, black_r)) +
+                       (max (g, black_g) - min (g, black_g)) + 
+                       (max (b, black_b) - min (b, black_b));
+
+               if (white_contrast > black_contrast) {          
+                       /* use white */
+                       name_text->set_color (ArdourCanvas::rgba_to_color (1.0, 1.0, 1.0, 1.0));
+               } else {
+                       /* use black */
+                       name_text->set_color (ArdourCanvas::rgba_to_color (0.0, 0.0, 0.0, 1.0));
+               }
+
+#if 0
+               double h, s, v;
+
+               ArdourCanvas::color_to_hsv (fill_color, h, s, v);
+
+               if (v == 0.0) {
+                       /* fill is black, set text to white */
+                       name_text->set_color (ArdourCanvas::rgba_to_color (1.0, 1.0, 1.0, 1.0));
+               } else if (v == 1.0) {
+                       /* fill is white, set text to black */
+                       name_text->set_color (ArdourCanvas::rgba_to_color (0.0, 0.0, 0.0, 1.0));
+               } else {
+
+                       h = fabs (fmod ((h - 180), 360.0)); /* complementary color */
+                       s = 1.0; /* fully saturate */
+                       v = 0.9; /* increase lightness/brightness/value */
+
+                       name_text->set_color (ArdourCanvas::hsv_to_color (h, s, v, 1.0));
+               }
+#endif
+
+       }
+       
        set_trim_handle_colors();
 }