From e39de97136c03c3fb6cb571a0b645616a2e9a15f Mon Sep 17 00:00:00 2001
From: Tim Allen <screwtape@froup.com>
Date: Mon, 12 Nov 2012 10:05:27 +1100
Subject: [PATCH] Update the SABR shader.

I read a little further in the thread and discovered an updated version
of the SABR shader:

    "Thanks to screwtape's sharp eyes I was able to adjust weighting and
    threshold values to prevent the curve flattening he described."

From:

    http://board.byuu.org/viewtopic.php?p=76944#p76944
---
 shaders/OpenGL/v1.0/SABR.shader | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/shaders/OpenGL/v1.0/SABR.shader b/shaders/OpenGL/v1.0/SABR.shader
index 2b6b66b..b5539e1 100644
--- a/shaders/OpenGL/v1.0/SABR.shader
+++ b/shaders/OpenGL/v1.0/SABR.shader
@@ -23,8 +23,6 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
-   (The original Cg version of the xBR family of shaders is available on
-   Github: https://github.com/twinaphex/common-shaders/tree/master/xBR )
 -->
 <shader language="GLSL">
   <vertex><![CDATA[
@@ -68,9 +66,9 @@
 
     const float coef = 2.0;
     // Threshold for if luminance values are "equal"
-    const float threshold = 15.0;
+    const float threshold = 20.0;
 
-    const float lum_weight = 64.0;
+    const float lum_weight = 48.0;
     // Conversion from RGB to Luminance
     const vec3 lum = vec3(0.2126, 0.7152, 0.0722);
     const vec3 lum_weighted = lum * lum_weight;
@@ -101,11 +99,11 @@
     }
 
     bvec4 lum_eq(vec4 A, vec4 B) {
-       return lessThan(lum_df(A, B), vec4(threshold));
+      return lessThan(lum_df(A, B), vec4(threshold));
     }
 
     vec4 lum_wd(vec4 a, vec4 b, vec4 c, vec4 d, vec4 e, vec4 f, vec4 g, vec4 h) {
-       return lum_df(a, b) + lum_df(a, c) + lum_df(d, e) + lum_df(d, f) + 4.0 * lum_df(g, h);
+      return lum_df(a, b) + lum_df(a, c) + lum_df(d, e) + lum_df(d, f) + 4.0 * lum_df(g, h);
     }
 
     void main() {
-- 
2.1.4