[Freeciv-Dev] (PR#11433) Fog of War rendering improvement

["Andreas Røsdal" <andrearo@xxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=11433 >

Following the discussion on how to do fog of war with alpha blending, I
did a little test to implement an improvement to the fog of war rendering.

It doesn't use alpha-blending, since you would need to use pixbufs.
Instead the brightness of every pixel is reduced by 50%, by iterating over
each pixel in the pixmap.

There is little or no performance hit that I can notice, but it would be a
good idea to do some benchmarking. Is is possible to get a frames/s
output?

Patch against CVS head, for the Gtk 2.x client.

Screenshot: http://www.stud.ntnu.no/~andrearo/scr.png

Andreas Røsdal

diff -ruN -X freeciv-cvs-Dec-08/diff_ignore 
freeciv-cvs-Dec-08/client/gui-gtk-2.0/mapview.c 
freeciv-fow/client/gui-gtk-2.0/mapview.c
--- freeciv-cvs-Dec-08/client/gui-gtk-2.0/mapview.c     2004-12-09 
17:06:35.000000000 +0100
+++ freeciv-fow/client/gui-gtk-2.0/mapview.c    2004-12-09 17:05:51.000000000 
+0100
@@ -877,22 +877,48 @@
     return;
   }
 
-  pixmap_put_sprite(pixmap, canvas_x, canvas_y, ssprite,
-                   0, 0, ssprite->width, ssprite->height);
-
-  /* I imagine this could be done more efficiently. Some pixels We first
-     draw from the sprite, and then draw black afterwards. It would be much
-     faster to just draw every second pixel black in the first place. */
   if (fog) {
+    int x, y;
+    GdkImage* ftile = gdk_drawable_get_image(ssprite->pixmap,
+                                             0, 0,
+                                             ssprite->width,
+                                             ssprite->height);
+    /* Iterate over all pixels, reducing brightness by 50%. */
+    for (x = 0; x < ssprite->width; x++) {
+      for (y = 0; y < ssprite->height; y++) {
+        guint32 pixel =  gdk_image_get_pixel(ftile, x, y);
+
+        guint8 red = (((pixel & ftile->visual->red_mask) << 
+             (32 - ftile->visual->red_shift 
+              - ftile->visual->red_prec)) >> 24) / 2; 
+        guint8 green = (((pixel & ftile->visual->green_mask) <<
+             (32 - ftile->visual->green_shift 
+              - ftile->visual->green_prec)) >> 24) / 2;
+        guint8 blue = (((pixel & ftile->visual->blue_mask) <<
+             (32 - ftile->visual->blue_shift 
+              - ftile->visual->blue_prec)) >> 24) / 2;
+        guint32 result = red << ftile->visual->red_shift
+                        | green << ftile->visual->green_shift          
+                        | blue << ftile->visual->blue_shift;
+
+        gdk_image_put_pixel(ftile, x , y, result);
+      }
+    }
+
     gdk_gc_set_clip_origin(fill_tile_gc, canvas_x, canvas_y);
     gdk_gc_set_clip_mask(fill_tile_gc, ssprite->mask);
-    gdk_gc_set_foreground(fill_tile_gc, colors_standard[COLOR_STD_BLACK]);
     gdk_gc_set_ts_origin(fill_tile_gc, canvas_x, canvas_y);
-    gdk_gc_set_stipple(fill_tile_gc, black50);
 
-    gdk_draw_rectangle(pixmap, fill_tile_gc, TRUE,
-                      canvas_x, canvas_y, ssprite->width, ssprite->height);
+    gdk_draw_image(pixmap, fill_tile_gc,
+                   ftile,
+                   0, 0,
+                   canvas_x, canvas_y,
+                   ssprite->width, ssprite->height);
     gdk_gc_set_clip_mask(fill_tile_gc, NULL);
+
+  } else {
+    pixmap_put_sprite(pixmap, canvas_x, canvas_y, ssprite,
+                      0, 0, ssprite->width, ssprite->height);
   }
 }