From 9e90f1407e5cc4b10b3a0e249674ceefc156c30b Mon Sep 17 00:00:00 2001
From: Ton Roosendaal <ton@blender.org>
Date: Thu, 24 Mar 2005 21:01:12 +0000
Subject: Bug fix 2303

The gamma functions in gammaCorrectionTables.c cannot be used to correct
and correct back with identical results... causing banding in rendering
pictures with halos.
---
 source/blender/render/intern/source/gammaCorrectionTables.c |  4 ++--
 source/blender/render/intern/source/rendercore.c            | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/source/blender/render/intern/source/gammaCorrectionTables.c b/source/blender/render/intern/source/gammaCorrectionTables.c
index 0e27aacd9e3..9273aa899ee 100644
--- a/source/blender/render/intern/source/gammaCorrectionTables.c
+++ b/source/blender/render/intern/source/gammaCorrectionTables.c
@@ -40,8 +40,8 @@
 #include <config.h>
 #endif
 
-/* There are two parts here: one for the old renderer, one for the unified   */
-/* renderer. we start with the latter.                                       */
+/* WARNING; optimized, cannot be used to do gamma(invgamma()) and expect    */
+/* result remain identical (ton)                                            */   
 
 /* Default gamma. For most CRTs, gamma ranges from 2.2 to 2.5 (Foley), so    */
 /* 2.35 seems appropriate enough. Experience teaches a different number      */
diff --git a/source/blender/render/intern/source/rendercore.c b/source/blender/render/intern/source/rendercore.c
index 75f106be7ab..e73c1a63413 100644
--- a/source/blender/render/intern/source/rendercore.c
+++ b/source/blender/render/intern/source/rendercore.c
@@ -451,9 +451,9 @@ static void scanlinehaloPS(int *rectz, long *rectdelta, float *rowbuf, short ys)
 							float *buf= rowbuf;
 							int xt;
 							for(xt=0; xt<R.rectx; xt++, buf+=4) {
-								buf[0]= invGammaCorrect(buf[0]);
-								buf[1]= invGammaCorrect(buf[1]);
-								buf[2]= invGammaCorrect(buf[2]);
+								buf[0]= sqrt(buf[0]);	// invers gamma 2.0
+								buf[1]= sqrt(buf[1]);
+								buf[2]= sqrt(buf[2]);
 							}
 							didgamma= 1;
 						}
@@ -526,9 +526,9 @@ static void scanlinehaloPS(int *rectz, long *rectdelta, float *rowbuf, short ys)
 		float *buf= rowbuf;
 		int xt;
 		for(xt=0; xt<R.rectx; xt++, buf+=4) {
-			buf[0]= gammaCorrect(buf[0]);
-			buf[1]= gammaCorrect(buf[1]);
-			buf[2]= gammaCorrect(buf[2]);
+			buf[0]*= (buf[0]);	// gamma 2.0
+			buf[1]*= (buf[1]);
+			buf[2]*= (buf[2]);
 		}
 	}
 
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