(svn r13640) -Codechange: make colours behind not fully solid objects less darker for BM_TRANSPARENT (for 32bpp blitters)

3 files changed, 34 insertions, 17 deletions

diff --git a/src/blitter/32bpp_anim.cpp b/src/blitter/32bpp_anim.cpp
index 9523c2dec..1c91911ff 100644
--- a/src/blitter/32bpp_anim.cpp
+++ b/src/blitter/32bpp_anim.cpp
@@ -136,15 +136,24 @@ inline void Blitter_32bppAnim::Draw(const Blitter::BlitterParams *bp, ZoomLevel
 					 *  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:
diff --git a/src/blitter/32bpp_base.hpp b/src/blitter/32bpp_base.hpp
index 30df9dd0e..1e9ae1d16 100644
--- a/src/blitter/32bpp_base.hpp
+++ b/src/blitter/32bpp_base.hpp
@@ -105,16 +105,17 @@ public:
 	/**
 	* 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);
 	}
 
 	/**
diff --git a/src/blitter/32bpp_optimized.cpp b/src/blitter/32bpp_optimized.cpp
index 6a6ad6542..717701bce 100644
--- a/src/blitter/32bpp_optimized.cpp
+++ b/src/blitter/32bpp_optimized.cpp
@@ -142,13 +142,20 @@ inline void Blitter_32bppOptimized::Draw(const Blitter::BlitterParams *bp, ZoomL
 					 *  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: