From 49049d90470eb3e94bda77d19ab7f7c57a0bd57f Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
Date: Tue, 30 Jun 2015 11:22:32 +0200
Subject: Fix simple semi-transparent blending of RGB32 on RGB30

We can not rely on the alpha being preserved as part of the source when
the source is converted to a2rgb30 which has much less alpha accuracy
instead we need to apply the alpha on the result.

Change-Id: Iac3104666980825e44ed3490370cdbe21dc68008
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
---
 src/gui/painting/qblendfunctions.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/gui/painting/qblendfunctions.cpp b/src/gui/painting/qblendfunctions.cpp
index b3710411c9..dbdd82e432 100644
--- a/src/gui/painting/qblendfunctions.cpp
+++ b/src/gui/painting/qblendfunctions.cpp
@@ -422,8 +422,8 @@ static void qt_blend_argb32pm_on_a2rgb30pm(uchar *destPixels, int dbpl,
         const_alpha = (const_alpha * 255) >> 8;
         for (int y=0; y<h; ++y) {
             for (int x=0; x<w; ++x) {
-                uint s = BYTE_MUL(src[x], const_alpha);
-                dst[x] = qConvertArgb32ToA2rgb30<PixelOrder>(s) + BYTE_MUL_RGB30(dst[x], 255 - qAlpha(s));
+                uint s = src[x];
+                dst[x] = BYTE_MUL_RGB30(qConvertArgb32ToA2rgb30<PixelOrder>(s), const_alpha) + BYTE_MUL_RGB30(dst[x], 255 - qt_div_255(qAlpha(s) * const_alpha));
             }
             dst = (quint32 *)(((uchar *) dst) + dbpl);
             src = (const quint32 *)(((const uchar *) src) + sbpl);
-- 
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