From f735bb053bb944b84c70b117297c7559b8b7c61c Mon Sep 17 00:00:00 2001
From: gewlitys <gewlitys@8092fc87-c524-0410-9efc-e669fe64eaf9>
Date: Wed, 16 Jul 2003 00:06:47 +0000
Subject: [PATCH] Fixed overflow bug with 32bpp bilinear,biadapt,biadv scalers

git-svn-id: svn://svn.code.sf.net/p/sc2/code/trunk@1054 8092fc87-c524-0410-9efc-e669fe64eaf9
---
 sc2/ChangeLog                                 |  1 +
 sc2/src/sc2code/libs/graphics/sdl/2xscalers.c | 43 +++++++++++++------
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/sc2/ChangeLog b/sc2/ChangeLog
index a9e8cf78f..35c2941c4 100644
--- a/sc2/ChangeLog
+++ b/sc2/ChangeLog
@@ -1,4 +1,5 @@
 Changes towards version 0.3:
+- Fixed overflow problem with 32bpp bilinear,biadapt,biadv scalers -Mika
 - MixSDL now handles resampling correctly (less cracklings);
   added cubic interpolation for high quality mode -Mika
 - Removed the redundant "GameExiting" variable -Michael
diff --git a/sc2/src/sc2code/libs/graphics/sdl/2xscalers.c b/sc2/src/sc2code/libs/graphics/sdl/2xscalers.c
index a5b84b3d3..de0064cd4 100644
--- a/sc2/src/sc2code/libs/graphics/sdl/2xscalers.c
+++ b/sc2/src/sc2code/libs/graphics/sdl/2xscalers.c
@@ -186,7 +186,19 @@ Scale_BlendPixels (SDL_PixelFormat* fmt, Uint32 pix1, Uint32 pix2)
 			 ) >> 1) & fmt->Gmask) |
 			((((pix1 & fmt->Bmask) +
 			   (pix2 & fmt->Bmask)
-			) >> 1) & fmt->Bmask);
+			 ) >> 1) & fmt->Bmask);
+}
+
+// blends two pixels with ratio 50% - 50% (safe for 32bpp surfaces)
+__inline__ Uint32
+Scale_BlendPixels_32bpp_safe (SDL_PixelFormat* fmt, Uint32 pix1, Uint32 pix2)
+{
+	return ((((((pix1 & fmt->Rmask) >> fmt->Rshift) +
+			((pix2 & fmt->Rmask) >> fmt->Rshift)) >> 1) << fmt->Rshift) & fmt->Rmask) |
+			((((((pix1 & fmt->Gmask) >> fmt->Gshift) +
+			((pix2 & fmt->Gmask) >> fmt->Gshift)) >> 1) << fmt->Gshift) & fmt->Gmask) |
+			((((((pix1 & fmt->Bmask) >> fmt->Bshift) +
+			((pix2 & fmt->Bmask) >> fmt->Bshift)) >> 1) << fmt->Bshift) & fmt->Bmask);
 }
 
 // compare pixels by their RGB
@@ -706,6 +718,7 @@ Scale_BiAdaptFilter (SDL_Surface *src, SDL_Surface *dst, SDL_Rect *r)
 	#define BIADAPT_GETPIX(p)        ( *(Uint32 *)(p) )
 	#define BIADAPT_SETPIX(p, c)     ( *(Uint32 *)(p) = (c) )
 	#define BIADAPT_BUF              Uint32
+	#define Scale_BlendPixels Scale_BlendPixels_32bpp_safe
 	{
 		BIADAPT_BUF *src_p = (BIADAPT_BUF *)src->pixels;
 		BIADAPT_BUF *dst_p = (BIADAPT_BUF *)dst->pixels;
@@ -899,7 +912,7 @@ Scale_BiAdaptFilter (SDL_Surface *src, SDL_Surface *dst, SDL_Rect *r)
 	#undef BIADAPT_GETPIX
 	#undef BIADAPT_SETPIX
 	#undef BIADAPT_BUF
-	#undef BIADAPT_CLR
+	#undef Scale_BlendPixels
 
 	}
 }
@@ -1877,6 +1890,7 @@ Scale_BiAdaptAdvFilter (SDL_Surface *src, SDL_Surface *dst, SDL_Rect *r)
 	#define BIADAPT_GETPIX(p)        ( *(Uint32 *)(p) )
 	#define BIADAPT_SETPIX(p, c)     ( *(Uint32 *)(p) = (c) )
 	#define BIADAPT_BUF              Uint32
+	#define Scale_BlendPixels Scale_BlendPixels_32bpp_safe
 	{
 		BIADAPT_BUF *src_p = (BIADAPT_BUF *)src->pixels;
 		BIADAPT_BUF *dst_p = (BIADAPT_BUF *)dst->pixels;
@@ -2324,6 +2338,7 @@ Scale_BiAdaptAdvFilter (SDL_Surface *src, SDL_Surface *dst, SDL_Rect *r)
 	#undef BIADAPT_GETPIX
 	#undef BIADAPT_SETPIX
 	#undef BIADAPT_BUF
+	#undef Scale_BlendPixels
 	}
 
 	#undef BIADAPT_CMPRGB
@@ -2585,18 +2600,18 @@ void Scale_BilinearFilter (SDL_Surface *src, SDL_Surface *dst, SDL_Rect *r)
 				fd = bilinear_table[j][3];
 
 				*dst_p++ = 
-					(((((p[0] & fmt->Rmask) * fa) +
-					((p[1] & fmt->Rmask) * fb) +
-					((p[2] & fmt->Rmask) * fc) +
-					((p[3] & fmt->Rmask) * fd)) >> 4) & fmt->Rmask) |
-					(((((p[0] & fmt->Gmask) * fa) +
-					((p[1] & fmt->Gmask) * fb) +
-					((p[2] & fmt->Gmask) * fc) +
-					((p[3] & fmt->Gmask) * fd)) >> 4) & fmt->Gmask) |
-					(((((p[0] & fmt->Bmask) * fa) +
-					((p[1] & fmt->Bmask) * fb) +
-					((p[2] & fmt->Bmask) * fc) +
-					((p[3] & fmt->Bmask) * fd)) >> 4) & fmt->Bmask);
+					(((((((p[0] & fmt->Rmask) >> fmt->Rshift) * fa) +
+					(((p[1] & fmt->Rmask) >> fmt->Rshift) * fb) +
+					(((p[2] & fmt->Rmask) >> fmt->Rshift) * fc) +
+					(((p[3] & fmt->Rmask) >> fmt->Rshift) * fd)) >> 4) << fmt->Rshift) & fmt->Rmask) |
+					(((((((p[0] & fmt->Gmask) >> fmt->Gshift) * fa) +
+					(((p[1] & fmt->Gmask) >> fmt->Gshift) * fb) +
+					(((p[2] & fmt->Gmask) >> fmt->Gshift) * fc) +
+					(((p[3] & fmt->Gmask) >> fmt->Gshift) * fd)) >> 4) << fmt->Gshift) & fmt->Gmask) |
+					(((((((p[0] & fmt->Bmask) >> fmt->Bshift) * fa) +
+					(((p[1] & fmt->Bmask) >> fmt->Bshift) * fb) +
+					(((p[2] & fmt->Bmask) >> fmt->Bshift) * fc) +
+					(((p[3] & fmt->Bmask) >> fmt->Bshift) * fd)) >> 4) << fmt->Bshift) & fmt->Bmask);
 
 				if (j & 2)
 				{