From 6e45cfae05dccca77437f738a699583b6e6ed202 Mon Sep 17 00:00:00 2001
From: divverent <divverent@d7cf8633-e32d-0410-b094-e92efae38249>
Date: Wed, 15 Dec 2010 12:01:47 +0000
Subject: [PATCH] care for the premultiplied-alpha flag when handling DDS files
 (use DXT2/DXT4 FOURCC when writing, and show a warning when loading if the
 type is wrong)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@10663 d7cf8633-e32d-0410-b094-e92efae38249
---
 gl_textures.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/gl_textures.c b/gl_textures.c
index 1e7b4500..b5affacb 100644
--- a/gl_textures.c
+++ b/gl_textures.c
@@ -1671,6 +1671,15 @@ int R_SaveTextureDDSFile(rtexture_t *rt, const char *filename, qboolean skipunco
 	case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT: ddsfourcc = "DXT3";bytesperblock = 16;break;
 	case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT: ddsfourcc = "DXT5";bytesperblock = 16;break;
 	}
+	// if premultiplied alpha, say so in the DDS file
+	if(glt->flags & TEXF_RGBMULTIPLYBYALPHA)
+	{
+		switch(internalformat)
+		{
+			case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT: ddsfourcc = "DXT2";break;
+			case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT: ddsfourcc = "DXT4";break;
+		}
+	}
 	if (!bytesperblock && skipuncompressed)
 		return -3; // skipped
 	memset(mipinfo, 0, sizeof(mipinfo));
@@ -1875,6 +1884,20 @@ rtexture_t *R_LoadTextureDDSFile(rtexturepool_t *rtexturepool, const char *filen
 	}
 	else if (!memcmp(dds+84, "DXT3", 4) || !memcmp(dds+84, "DXT2", 4))
 	{
+		if(!memcmp(dds+84, "DXT2", 4))
+		{
+			if(!(flags & TEXF_RGBMULTIPLYBYALPHA))
+			{
+				Con_Printf("^1%s: expecting DXT3 image without premultiplied alpha, got DXT2 image with premultiplied alpha\n", filename);
+			}
+		}
+		else
+		{
+			if(flags & TEXF_RGBMULTIPLYBYALPHA)
+			{
+				Con_Printf("^1%s: expecting DXT2 image without premultiplied alpha, got DXT3 image without premultiplied alpha\n", filename);
+			}
+		}
 		if(!vid.support.ext_texture_compression_s3tc)
 		{
 			Mem_Free(dds);
@@ -1894,6 +1917,20 @@ rtexture_t *R_LoadTextureDDSFile(rtexturepool_t *rtexturepool, const char *filen
 	}
 	else if (!memcmp(dds+84, "DXT5", 4) || !memcmp(dds+84, "DXT4", 4))
 	{
+		if(!memcmp(dds+84, "DXT4", 4))
+		{
+			if(!(flags & TEXF_RGBMULTIPLYBYALPHA))
+			{
+				Con_Printf("^1%s: expecting DXT5 image without premultiplied alpha, got DXT4 image with premultiplied alpha\n", filename);
+			}
+		}
+		else
+		{
+			if(flags & TEXF_RGBMULTIPLYBYALPHA)
+			{
+				Con_Printf("^1%s: expecting DXT4 image without premultiplied alpha, got DXT5 image without premultiplied alpha\n", filename);
+			}
+		}
 		if(!vid.support.ext_texture_compression_s3tc)
 		{
 			Mem_Free(dds);
-- 
2.39.2