From f384349dfb857247a9f0dcc367b501eea4b0d520 Mon Sep 17 00:00:00 2001
From: reimar <reimar@b3059339-0415-0410-9bf9-f77b7e298cf2>
Date: Sun, 25 Sep 2005 16:17:03 +0000
Subject: [PATCH] contrast 0 should lead to a grey, not a black image

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@16590 b3059339-0415-0410-9bf9-f77b7e298cf2
---
 libvo/gl_common.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libvo/gl_common.c b/libvo/gl_common.c
index 936c4618a3..63f70cee90 100644
--- a/libvo/gl_common.c
+++ b/libvo/gl_common.c
@@ -563,6 +563,11 @@ static void glSetupYUVFragprog(float brightness, float contrast,
   rc = (-16 * ry + (-128) * ru + (-128) * rv) / 255.0 + brightness;
   gc = (-16 * gy + (-128) * gu + (-128) * gv) / 255.0 + brightness;
   bc = (-16 * by + (-128) * bu + (-128) * bv) / 255.0 + brightness;
+  // these "center" contrast control so that e.g. a contrast of 0
+  // leads to a grey image, not a black one
+  rc += 0.5 - contrast / 2.0;
+  gc += 0.5 - contrast / 2.0;
+  bc += 0.5 - contrast / 2.0;
   rgamma = 1.0 / rgamma;
   ggamma = 1.0 / ggamma;
   bgamma = 1.0 / bgamma;