From 8f980fe24cb3144bf7bcb6dbcb4f29ef554fbaa3 Mon Sep 17 00:00:00 2001
From: Simon Howard
Date: Sun, 16 Oct 2011 16:59:19 +0000
Subject: Zero out bottom two bits of palette data, to more accurately emulate
 the PC hardware that only supports 6 bits per channel (thanks GhostlyDeath).

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 2433
---
 NEWS          |  2 ++
 src/i_video.c | 11 +++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index 425da376..36d7180a 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,8 @@
      * Updated COPYING to current version of GPL2 (thanks Rahul
        Sundaram).
      * Fix bug with detection of IWAD type by filename (thanks mether).
+     * Reduce palette accuracy to 6 bits per channel, to more accurately
+       emulate the PC VGA hardware (thanks GhostlyDeath).
 
 1.6.0 (2011-05-17):
 
diff --git a/src/i_video.c b/src/i_video.c
index 15e4a6b7..d671a228 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -956,11 +956,14 @@ void I_SetPalette (byte *doompalette)
 {
     int i;
 
-    for (i=0; i<256; ++i) 
+    for (i=0; i<256; ++i)
     {
-        palette[i].r = gammatable[usegamma][*doompalette++];
-        palette[i].g = gammatable[usegamma][*doompalette++];
-        palette[i].b = gammatable[usegamma][*doompalette++];
+        // Zero out the bottom two bits of each channel - the PC VGA
+        // controller only supports 6 bits of accuracy.
+
+        palette[i].r = gammatable[usegamma][*doompalette++] & ~3;
+        palette[i].g = gammatable[usegamma][*doompalette++] & ~3;
+        palette[i].b = gammatable[usegamma][*doompalette++] & ~3;
     }
 
     palette_to_set = true;
-- 
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