1 files changed, 14 insertions, 9 deletions

diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h
index 418294c56d..0f98b07229 100644
--- a/src/gui/painting/qdrawhelper_p.h
+++ b/src/gui/painting/qdrawhelper_p.h
@@ -171,6 +171,8 @@ extern MemRotateFunc qMemRotateFunctions[QImage::NImageFormats][3];
 extern DrawHelper qDrawHelper[QImage::NImageFormats];
 
 void qBlendTexture(int count, const QSpan *spans, void *userData);
+extern void qt_memfill32(quint32 *dest, quint32 value, int count);
+extern void qt_memfill16(quint16 *dest, quint16 value, int count);
 
 typedef void (QT_FASTCALL *CompositionFunction)(uint *Q_DECL_RESTRICT dest, const uint *Q_DECL_RESTRICT src, int length, uint const_alpha);
 typedef void (QT_FASTCALL *CompositionFunctionSolid)(uint *dest, int length, uint color, uint const_alpha);
@@ -386,8 +388,6 @@ static inline qreal qRadialDeterminant(qreal a, qreal b, qreal c)
     return (b * b) - (4 * a * c);
 }
 
-extern void (*qt_memfill32)(quint32 *dest, quint32 value, int count);
-
 template <class RadialFetchFunc> Q_STATIC_TEMPLATE_FUNCTION
 const uint * QT_FASTCALL qt_fetch_radial_gradient_template(uint *buffer, const Operator *op, const QSpanData *data,
                                                            int y, int x, int length)
@@ -691,12 +691,17 @@ static Q_ALWAYS_INLINE uint BYTE_MUL_RGB16_32(uint x, uint a) {
     return t;
 }
 
-#define INV_PREMUL(p)                                   \
-    (qAlpha(p) == 0 ? 0 :                               \
-    ((qAlpha(p) << 24)                                  \
-     | (((255*qRed(p))/ qAlpha(p)) << 16)               \
-     | (((255*qGreen(p)) / qAlpha(p))  << 8)            \
-     | ((255*qBlue(p)) / qAlpha(p))))
+static Q_ALWAYS_INLINE uint INV_PREMUL(uint p) {
+    const uint alpha = qAlpha(p);
+    if (alpha == 255)
+        return p;
+    if (alpha == 0)
+        return 0;
+    // (p*(0x00ff00ff/alpha)) >> 16 == (p*255)/alpha for all p and alpha <= 256.
+    const uint invAlpha = 0x00ff00ffU / alpha;
+    // We add 0x8000 to get even rounding. The rounding also ensures that PREMUL(INV_PREMUL(p)) == p for all p.
+    return qRgba((qRed(p)*invAlpha + 0x8000)>>16, (qGreen(p)*invAlpha + 0x8000)>>16, (qBlue(p)*invAlpha + 0x8000)>>16, alpha);
+}
 
 struct quint24 {
     quint24(uint value);
@@ -726,7 +731,6 @@ template<> inline void qt_memfill(quint32 *dest, quint32 color, int count)
 
 template<> inline void qt_memfill(quint16 *dest, quint16 color, int count)
 {
-    extern void (*qt_memfill16)(quint16 *dest, quint16 value, int count);
     qt_memfill16(dest, color, count);
 }
 
@@ -1031,6 +1035,7 @@ struct QPixelLayout
     BPP bpp;
     ConvertFunc convertToARGB32PM;
     ConvertFunc convertFromARGB32PM;
+    ConvertFunc convertFromRGB32;
 };
 
 typedef const uint *(QT_FASTCALL *FetchPixelsFunc)(uint *buffer, const uchar *src, int index, int count);