Restore 54% transparency on title screen, use 70% on dialogs.

images/dialogs/README

@@ -3,5 +3,16 @@ images is named by the part before the first dash, which is a style
 referenced by name in the Wesnoth UI code.
 
 The 'transparent' images have some alpha transparency; they look like
-smoked-glass overlays on the terrain or whatever else is underneath them.
-The 'opaque' images are geometrically the same, but opaque.
+smoked-glass overlays on the terrain or whatever else is underneath
+them.  Each transparent style has a suffix which is its opacity
+percentage (100-alpha).  The 'opaque' images are geometrically the
+same, but opaque.  They could be called 'translucent100', but aren't
+for reasons that are basically historical.
+
+Note that the translucent and opaque styles differ only in the background
+images, sharing borders.  This uses a little more space but simplifies 
+the code.
+
+The directory also contains some background images of different opacity
+levels, just so they're handy for tuning.  They cost less than 0.5K each
+to keep around.

src/construct_dialog.hpp

@@ -276,7 +276,7 @@ class message_dialog : public gui::dialog
 {
 public:
 	message_dialog(display &disp, const std::string& title="", const std::string& message="", const gui::DIALOG_TYPE type=gui::MESSAGE)
-		: dialog(disp, title, message, type, "translucent"), prevent_misclick_until_(0)
+		: dialog(disp, title, message, type, "translucent70"), prevent_misclick_until_(0)
 	{}
 	~message_dialog();
 	int show(msecs minimum_lifetime = three_blinks);

src/titlescreen.cpp

@@ -296,7 +296,7 @@ TITLE_RESULT show_title(display& screen, config& tips_of_day, int* ntip)
 
 	SDL_Rect main_dialog_area = {menu_xbase-padding,menu_ybase-padding,max_width+padding*2,menu_yincr*(nbuttons-1)+buttons.back().height()+padding*2};
 
-    const std::string style = "opaque";
+    const std::string style = "translucent54";
 	gui::dialog_frame main_frame(screen.video(), "", &style);
 	main_frame.layout(main_dialog_area);
 	main_frame.draw_background();