From 6974efece77c1abe99172a4ef1c4b06b3ccc04ce Mon Sep 17 00:00:00 2001
From: avolkov <avolkov@8092fc87-c524-0410-9efc-e669fe64eaf9>
Date: Mon, 28 Nov 2005 05:37:17 +0000
Subject: [PATCH] Alpha channel friendly collider

git-svn-id: svn://svn.code.sf.net/p/sc2/code/trunk@2018 8092fc87-c524-0410-9efc-e669fe64eaf9
---
 sc2/src/sc2code/libs/graphics/sdl/3do_funcs.c | 35 ++++++++++++++++---
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/sc2/src/sc2code/libs/graphics/sdl/3do_funcs.c b/sc2/src/sc2code/libs/graphics/sdl/3do_funcs.c
index d404768a9..b61b7cce1 100644
--- a/sc2/src/sc2code/libs/graphics/sdl/3do_funcs.c
+++ b/sc2/src/sc2code/libs/graphics/sdl/3do_funcs.c
@@ -189,7 +189,8 @@ _image_intersect (PIMAGE_BOX box1, PIMAGE_BOX box2, PRECT rect)
 	SDL_Surface *img1, *img2;
 	int img1w, img1xpos, img1ypos, img2w, img2xpos, img2ypos;
 	int x,y;
-	Uint32 img1colourkey, img2colourkey;
+	Uint32 img1key, img2key;
+	Uint32 img1mask, img2mask;
 	GetPixelFn getpixel1, getpixel2;
 
 	img1 = (SDL_Surface *)box1->FramePtr->image->NormalImg;
@@ -201,19 +202,43 @@ _image_intersect (PIMAGE_BOX box1, PIMAGE_BOX box2, PRECT rect)
 	img1w = img1->w;
 	img1xpos = box1->Box.corner.x;
 	img1ypos = box1->Box.corner.y;
-	img1colourkey = img1->format->colorkey;
+	if (img1->format->Amask)
+	{	// use alpha transparency info
+		img1mask = img1->format->Amask;
+		// consider any not fully transparent pixel collidable
+		img1key = 0;
+	}
+	else
+	{	// colorkey transparency
+		img1mask = ~img1->format->Amask;
+		img1key = img1->format->colorkey & img1mask;
+	}
 
 	img2w = img2->w;
 	img2xpos = box2->Box.corner.x;
 	img2ypos = box2->Box.corner.y;
-	img2colourkey = img2->format->colorkey;
+	if (img2->format->Amask)
+	{	// use alpha transparency info
+		img2mask = img2->format->Amask;
+		// consider any not fully transparent pixel collidable
+		img2key = 0;
+	}
+	else
+	{	// colorkey transparency
+		img2mask = ~img2->format->Amask;
+		img2key = img2->format->colorkey & img2mask;
+	}
 
 	for (y = rect->corner.y; y < rect->corner.y + rect->extent.height; ++y)
 	{
 		for (x = rect->corner.x; x < rect->corner.x + rect->extent.width; ++x)
 		{
-			if ((getpixel1(img1, x - img1xpos, y - img1ypos) != img1colourkey) &&
-					(getpixel2(img2, x - img2xpos, y - img2ypos) != img2colourkey))
+			Uint32 p1 = getpixel1(img1, x - img1xpos, y - img1ypos)
+						& img1mask;
+			Uint32 p2 = getpixel2(img2, x - img2xpos, y - img2ypos)
+						& img2mask;
+			
+			if ((p1 != img1key) && (p2 != img2key))
 			{
 				return TRUE;
 			}