From 7e6aa1b4a9cda2351c6716cfced0546aaa3d52d8 Mon Sep 17 00:00:00 2001
From: Willem Jan Palenstijn
Date: Thu, 4 Nov 2010 19:17:44 +0000
Subject: SCI: Use gamma 2.2 for blending undithered colours

svn-id: r54069
---
 engines/sci/graphics/palette.cpp | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

(limited to 'engines/sci/graphics')

diff --git a/engines/sci/graphics/palette.cpp b/engines/sci/graphics/palette.cpp
index 76b2ed53fc..96646237ee 100644
--- a/engines/sci/graphics/palette.cpp
+++ b/engines/sci/graphics/palette.cpp
@@ -192,6 +192,16 @@ void GfxPalette::modifyAmigaPalette(byte *data) {
 	_screen->setPalette(&_sysPalette);
 }
 
+static byte blendColours(byte c1, byte c2) {
+	// linear:
+	// return (c1/2+c2/2)+(c1&1+c2&1)/2;
+
+	// gamma 2.2
+	double t = 0.5 + (pow (c1/255.0, 2.2/1.0) * 255.0) + 
+	           0.5 + (pow (c2/255.0, 2.2/1.0) * 255.0);
+	return (byte)(0.5 + (pow (0.5*t/255.0, 1.0/2.2) * 255.0));
+}
+
 void GfxPalette::setEGA() {
 	int curColor;
 	byte color1, color2;
@@ -219,9 +229,10 @@ void GfxPalette::setEGA() {
 	for (curColor = 0x10; curColor <= 0xFE; curColor++) {
 		_sysPalette.colors[curColor].used = 1;
 		color1 = curColor & 0x0F; color2 = curColor >> 4;
-		_sysPalette.colors[curColor].r = (_sysPalette.colors[color1].r >> 1) + (_sysPalette.colors[color2].r >> 1);
-		_sysPalette.colors[curColor].g = (_sysPalette.colors[color1].g >> 1) + (_sysPalette.colors[color2].g >> 1);
-		_sysPalette.colors[curColor].b = (_sysPalette.colors[color1].b >> 1) + (_sysPalette.colors[color2].b >> 1);
+
+		_sysPalette.colors[curColor].r = blendColours(_sysPalette.colors[color1].r, _sysPalette.colors[color2].r);
+		_sysPalette.colors[curColor].g = blendColours(_sysPalette.colors[color1].g, _sysPalette.colors[color2].g);
+		_sysPalette.colors[curColor].b = blendColours(_sysPalette.colors[color1].b, _sysPalette.colors[color2].b);
 	}
 	_sysPalette.timestamp = 1;
 	setOnScreen();
-- 
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