From 3c572f8395e0735ae8dd1af62369a8eb43f84518 Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Sun, 17 Mar 2024 11:20:55 +0700
Subject: [PATCH] add comment about "Carmack's typo"

---
 src/v_video.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/v_video.c b/src/v_video.c
index 18dcadc0..2124e2aa 100644
--- a/src/v_video.c
+++ b/src/v_video.c
@@ -208,6 +208,8 @@ void V_InitColorTranslation(void)
         double green = *palsrc++ / 256.0;
         double blue  = *palsrc++ / 256.0;
 
+        // formula is taken from dcolors.c preseving "Carmack's typo"
+        // https://doomwiki.org/wiki/Carmack%27s_typo
         int gray = (red * 0.299 + green * 0.587 + blue * 0.144) * 255;
         invul_gray[i] = I_GetPaletteIndex(playpal, gray, gray, gray);
     }