From 2042c6d5701e5bf9431f5886e5440f68d3e57d38 Mon Sep 17 00:00:00 2001
From: Max Horn
Date: Mon, 26 Jan 2009 16:45:21 +0000
Subject: Slightly improved interpolate32_1_1

svn-id: r36075
---
 graphics/scaler/intern.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/graphics/scaler/intern.h b/graphics/scaler/intern.h
index 2e3760b70a..8f1b546685 100644
--- a/graphics/scaler/intern.h
+++ b/graphics/scaler/intern.h
@@ -40,12 +40,13 @@
 
 /**
  * Interpolate two 16 bit pixel *pairs* at once with equal weights 1.
- * In particular, A and B can contain two pixels/each in the upper
- * and lower halves.
+ * In particular, p1 and p2 can contain two pixels each in the upper
+ * and lower halves. Requires only 5 operations!
+ * See <http://www.slack.net/~ant/info/rgb_mixing.html> for details on how this works.
  */
 template<int bitFormat>
-static inline uint32 interpolate32_1_1(uint32 A, uint32 B) {
-	return (((A & kHighBitsMask) + (B & kHighBitsMask)) >> 1) + (A & B & kLowBitsMask);
+static inline uint32 interpolate32_1_1(uint32 p1, uint32 p2) {
+	return (p1 + p2 - ((p1 ^ p2) & kLowBitsMask)) >> 1; 
 }
 
 /**
-- 
cgit v1.2.3