--- a/src/blitter/32bpp_anim.cpp	Thu Jun 26 15:46:19 2008 +0000
+++ b/src/blitter/32bpp_anim.cpp	Thu Jun 26 16:47:29 2008 +0000
@@ -136,15 +136,24 @@
 					 *  we produce a result the newgrf maker didn't expect ;) */
 
 					/* Make the current color a bit more black, so it looks like this image is transparent */
-					src_px += n;
 					src_n += n;
-
-					do {
-						*dst = MakeTransparent(*dst, 192);
-						*anim = remap[*anim];
-						anim++;
-						dst++;
-					} while (--n != 0);
+					if (src_px->a == 255) {
+						src_px += n;
+						do {
+							*dst = MakeTransparent(*dst, 3, 4);
+							*anim = remap[*anim];
+							anim++;
+							dst++;
+						} while (--n != 0);
+					} else {
+						do {
+							*dst = MakeTransparent(*dst, (256 * 4 - src_px->a), 256 * 4);
+							*anim = remap[*anim];
+							anim++;
+							dst++;
+							src_px++;
+						} while (--n != 0);
+					}
 					break;
 
 				default:

--- a/src/blitter/32bpp_base.hpp	Thu Jun 26 15:46:19 2008 +0000
+++ b/src/blitter/32bpp_base.hpp	Thu Jun 26 16:47:29 2008 +0000
@@ -105,16 +105,17 @@
 	/**
 	* Make a pixel looks like it is transparent.
 	* @param colour the colour already on the screen.
-	* @param amount the amount of transparency, times 256.
+	* @param nom the amount of transparency, nominator, makes colour lighter.
+	* @param denom denominator, makes colour darker.
 	* @return the new colour for the screen.
 	*/
-	static inline uint32 MakeTransparent(uint32 colour, uint amount)
+	static inline uint32 MakeTransparent(uint32 colour, uint nom, uint denom = 256)
 	{
 		uint r = GB(colour, 16, 8);
 		uint g = GB(colour, 8,  8);
 		uint b = GB(colour, 0,  8);
 
-		return ComposeColour(0xFF, r * amount / 256, g * amount / 256, b * amount / 256);
+		return ComposeColour(0xFF, r * nom / denom, g * nom / denom, b * nom / denom);
 	}
 
 	/**

--- a/src/blitter/32bpp_optimized.cpp	Thu Jun 26 15:46:19 2008 +0000
+++ b/src/blitter/32bpp_optimized.cpp	Thu Jun 26 16:47:29 2008 +0000
@@ -142,13 +142,20 @@
 					 *  we produce a result the newgrf maker didn't expect ;) */
 
 					/* Make the current color a bit more black, so it looks like this image is transparent */
-					src_px += n;
 					src_n += n;
-
-					do {
-						*dst = MakeTransparent(*dst, 192);
-						dst++;
-					} while (--n != 0);
+					if (src_px->a == 255) {
+						src_px += n;
+						do {
+							*dst = MakeTransparent(*dst, 3, 4);
+							dst++;
+						} while (--n != 0);
+					} else {
+						do {
+							*dst = MakeTransparent(*dst, (256 * 4 - src_px->a), 256 * 4);
+							dst++;
+							src_px++;
+						} while (--n != 0);
+					}
 					break;
 
 				default: