[Performous-commit] John Stumpo : Fix the SDL_image image loading code' s handling of images that contain an alpha channel.

[John S. <jst...@us...>]

Module: performous
Branch: master
Commit: 301e581350142cd2082eae906978218203e1b26a

Author: John Stumpo <st...@js...>
Date:   Sun Dec 27 15:37:52 2009 -0500

Fix the SDL_image image loading code's handling of images that contain an alpha channel.

---

 game/surface.cc |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/game/surface.cc b/game/surface.cc
index a72f769..54ff5f2 100644
--- a/game/surface.cc
+++ b/game/surface.cc
@@ -95,7 +95,12 @@ template <typename T> void loader(T& target, std::string filename, bool autocrop
 		if (imgsurf == NULL) {
 			throw std::runtime_error("Unable to load " + filename + ": " + IMG_GetError());
 		}
-		// Copy the image to an RGBA surface to ensure that it is indeed RGBA.
+		// If an alpha channel is present in the source, ensure that SDL_SRCALPHA is not set on it
+		// so the alpha actually makes it onto the destination surface.
+		if (imgsurf->format->Amask != 0) {
+			SDL_SetAlpha(imgsurf, 0, 0);
+		}
+		// Copy the image to an RGBA surface to ensure that it is indeed RGBA with the right pixel layout.
 		SDL_Surface* rgbasurf = SDL_CreateRGBSurface(SDL_SWSURFACE, imgsurf->w, imgsurf->h, 32,
 #if SDL_BYTEORDER == SDL_BIGENDIAN
 		  0xff000000, 0x00ff0000, 0x0000ff00, 0x000000ff