diff -r 56d2f2d5aad8 -r 59a6d65fcb60 hedgewars/uLand.pas
--- a/hedgewars/uLand.pas	Sun Jan 19 00:18:28 2014 +0400
+++ b/hedgewars/uLand.pas	Sun Jan 19 13:41:11 2014 +0100
@@ -60,6 +60,61 @@
     end;
 end;
 
+{ this will make invisible pixels that have a visible neighbor have the
+  same color as their visible neighbor, so that bilinear filtering won't
+  display a "wrongly" colored border when zoomed in }
+procedure PrettifyLandAlpha();
+var
+    x, y, lastx, lasty: Longword;
+    lpi, cpi, bpi: boolean; // was last/current/bottom neighbor pixel invisible?
+begin
+    lasty:= LAND_HEIGHT - 1;
+    lastx:= LAND_WIDTH - 1;
+    if (cReducedQuality and rqBlurryLand) <> 0 then
+        begin
+        lasty:= lasty div 2;
+        lastx:= lastx div 2;
+        end;
+    for y:= 0 to lasty do
+        for x:= 0 to lastx do
+            begin
+            // use first pixel in row as starting point
+            //LandPixels[y, x]:= (LandPixels[y, x] and (BMask or GMask or AMask));
+            if x = 0 then
+                lpi:= ((LandPixels[y, x] and AMask) = 0)
+            else
+                begin
+                cpi:= ((LandPixels[y, x] and AMask) = 0);
+                if lpi <> cpi then
+                    begin
+                    // invisible pixels get colors from visible neighbors
+                    if cpi then
+                        begin
+                        LandPixels[y, x]:= LandPixels[y, x-1] and not AMask;
+                        // as this pixel is invisible and already colored correctly now, no point in further comparing it
+                        lpi:= cpi;
+                        continue;
+                        end
+                    else
+                        LandPixels[y, x-1]:= LandPixels[y, x] and not AMask;
+                    lpi:= cpi;
+                    end;
+                end;
+            // also check bottom neighbor, lpi is now current pixel info
+            if y < lasty - 1 then
+                begin
+                bpi:= ((LandPixels[y+1, x] and AMask) = 0);
+                if cpi <> bpi then
+                    begin
+                    if cpi then
+                        LandPixels[y, x]:= LandPixels[y+1, x] and not AMask
+                    else
+                        LandPixels[y+1, x]:= LandPixels[y, x] and not AMask;
+                    end;
+                end
+            end;
+end;
+
 
 procedure DrawBorderFromImage(Surface: PSDL_Surface);
 var tmpsurf: PSDL_Surface;
@@ -811,6 +866,8 @@
                 LandPixels[y,x]:= w or (LandPixels[y div 2, x div 2] and AMask)
                 end
     end;
+
+PrettifyLandAlpha();
 end;
 
 procedure GenPreview(out Preview: TPreview);