From 6d4ef0ff8fd30e5f50f6f770d651a51584e5cfdc Mon Sep 17 00:00:00 2001
From: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>
Date: Tue, 15 Mar 2011 09:39:13 +0100
Subject: Fix grayscale antialiasing with DirectWrite engine

The code that converted DirectWrite's output to grayscale in
alphaMapForGlyph() had a bunch of copy-paste errors and had obviously
not been tested properly. We invert the input to the gamma function to
get the right curve and then invert the output back. See windows
font engine for comparison.

Reviewed-by: Jiang Jiang
---
 src/gui/text/qfontenginedirectwrite.cpp | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/src/gui/text/qfontenginedirectwrite.cpp b/src/gui/text/qfontenginedirectwrite.cpp
index 23fff0d..af5bab2 100644
--- a/src/gui/text/qfontenginedirectwrite.cpp
+++ b/src/gui/text/qfontenginedirectwrite.cpp
@@ -485,12 +485,7 @@ QImage QFontEngineDirectWrite::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPo
         uint *src = (uint*) im.scanLine(y);
         uchar *dst = indexed.scanLine(y);
         for (int x=0; x<im.width(); ++x) {
-            *dst = qGray(*src);
-            if (QNativeImage::systemFormat() == QImage::Format_RGB16)
-                *dst = 255 - qGray(*src);
-            else
-                *dst = 255 - (qt_pow_gamma[qGray(*src)] * 255. / 2047.);
-
+            *dst = 255 - (qt_pow_gamma[qGray(0xffffffff - *src)] * 255. / 2047.);
             ++dst;
             ++src;
         }
-- 
cgit v0.12