Add Grayscale16 Image Format

[ChangeLog][QtGui][QImage] Added support for 16-bit grayscale format.

Together-with: Aaron Linville<aaron@linville.org>
Task-number: QTBUG-41176
Change-Id: I5fe4f54a55ebe1413aa71b882c19627fe22362ac
Reviewed-by: Nick D'Ademo <nickdademo@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

14 files changed, 348 insertions, 89 deletions

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 0105f1decd..b6d93331e6 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -288,6 +288,7 @@ bool QImageData::checkForAlphaPixels() const
     case QImage::Format_BGR30:
     case QImage::Format_RGB30:
     case QImage::Format_Grayscale8:
+    case QImage::Format_Grayscale16:
     case QImage::Format_RGBX64:
         break;
     case QImage::Format_Invalid:
@@ -710,6 +711,7 @@ bool QImageData::checkForAlphaPixels() const
     \value Format_A2RGB30_Premultiplied    The image is stored using a 32-bit premultiplied ARGB format (2-10-10-10). (added in Qt 5.4)
     \value Format_Alpha8     The image is stored using an 8-bit alpha only format. (added in Qt 5.5)
     \value Format_Grayscale8 The image is stored using an 8-bit grayscale format. (added in Qt 5.5)
+    \value Format_Grayscale16 The image is stored using an 16-bit grayscale format. (added in Qt 5.13)
     \value Format_RGBX64     The image is stored using a 64-bit halfword-ordered RGB(x) format (16-16-16-16).
                              This is the same as the Format_RGBX64 except alpha must always be 65535. (added in Qt 5.12)
     \value Format_RGBA64     The image is stored using a 64-bit halfword-ordered RGBA format (16-16-16-16). (added in Qt 5.12)
@@ -2038,6 +2040,7 @@ static bool highColorPrecision(QImage::Format format)
     case QImage::Format_RGBX64:
     case QImage::Format_RGBA64:
     case QImage::Format_RGBA64_Premultiplied:
+    case QImage::Format_Grayscale16:
         return true;
     default:
         break;
@@ -2531,6 +2534,10 @@ QColor QImage::pixelColor(int x, int y) const
     case Format_RGBA64_Premultiplied:
         c = reinterpret_cast<const QRgba64 *>(s)[x];
         break;
+    case Format_Grayscale16: {
+        quint16 v = reinterpret_cast<const quint16 *>(s)[x];
+        return QColor(qRgba64(v, v, v, 0xffff));
+    }
     default:
         c = QRgba64::fromArgb32(pixel(x, y));
         break;
@@ -2641,6 +2648,7 @@ bool QImage::allGray() const
     case Format_Alpha8:
         return false;
     case Format_Grayscale8:
+    case Format_Grayscale16:
         return true;
     case Format_RGB32:
     case Format_ARGB32:
@@ -2707,7 +2715,7 @@ bool QImage::isGrayscale() const
     if (d->format == QImage::Format_Alpha8)
         return false;
 
-    if (d->format == QImage::Format_Grayscale8)
+    if (d->format == QImage::Format_Grayscale8 || d->format == QImage::Format_Grayscale16)
         return true;
 
     switch (depth()) {
@@ -3341,6 +3349,7 @@ QImage QImage::rgbSwapped_helper() const
         break;
     case Format_Alpha8:
     case Format_Grayscale8:
+    case Format_Grayscale16:
         return *this;
     case Format_Mono:
     case Format_MonoLSB:
@@ -3452,6 +3461,7 @@ void QImage::rgbSwapped_inplace()
         break;
     case Format_Alpha8:
     case Format_Grayscale8:
+    case Format_Grayscale16:
         return;
     case Format_Mono:
     case Format_MonoLSB:
@@ -5349,6 +5359,19 @@ static Q_CONSTEXPR QPixelFormat pixelformats[] = {
                      /*PREMULTIPLIED*/     QPixelFormat::Premultiplied,
                      /*INTERPRETATION*/    QPixelFormat::UnsignedShort,
                      /*BYTE ORDER*/        QPixelFormat::CurrentSystemEndian),
+        //QImage::Format_Grayscale16:
+        QPixelFormat(QPixelFormat::Grayscale,
+                    /*GRAY*/               16,
+                    /*SECOND*/             0,
+                    /*THIRD*/              0,
+                    /*FOURTH*/             0,
+                    /*FIFTH*/              0,
+                    /*ALPHA*/              0,
+                    /*ALPHA USAGE*/       QPixelFormat::IgnoresAlpha,
+                    /*ALPHA POSITION*/    QPixelFormat::AtBeginning,
+                    /*PREMULTIPLIED*/     QPixelFormat::NotPremultiplied,
+                    /*INTERPRETATION*/    QPixelFormat::UnsignedShort,
+                    /*BYTE ORDER*/        QPixelFormat::CurrentSystemEndian),
 };
 Q_STATIC_ASSERT(sizeof(pixelformats) / sizeof(*pixelformats) == QImage::NImageFormats);
 
diff --git a/src/gui/image/qimage.h b/src/gui/image/qimage.h
index 4b7a3b1ead..7a1f37c5cf 100644
--- a/src/gui/image/qimage.h
+++ b/src/gui/image/qimage.h
@@ -128,10 +128,7 @@ public:
         Format_RGBX64,
         Format_RGBA64,
         Format_RGBA64_Premultiplied,
-#if 0
-        // reserved for future use
         Format_Grayscale16,
-#endif
 #ifndef Q_QDOC
         NImageFormats
 #endif
diff --git a/src/gui/image/qimage_conversions.cpp b/src/gui/image/qimage_conversions.cpp
index 215dd33499..ea9347183e 100644
--- a/src/gui/image/qimage_conversions.cpp
+++ b/src/gui/image/qimage_conversions.cpp
@@ -1447,6 +1447,56 @@ static bool convert_RGBA64PM_to_RGBA64_inplace(QImageData *data, Qt::ImageConver
     return true;
 }
 
+static void convert_gray16_to_RGBA64(QImageData *dest, const QImageData *src, Qt::ImageConversionFlags)
+{
+    Q_ASSERT(src->format == QImage::Format_Grayscale16);
+    Q_ASSERT(dest->format == QImage::Format_RGBA64 || dest->format == QImage::Format_RGBX64 ||
+             dest->format == QImage::Format_RGBA64_Premultiplied);
+    Q_ASSERT(src->width == dest->width);
+    Q_ASSERT(src->height == dest->height);
+
+    const qsizetype sbpl = src->bytes_per_line;
+    const qsizetype dbpl = dest->bytes_per_line;
+    const uchar *src_data = src->data;
+    uchar *dest_data = dest->data;
+
+    for (int i = 0; i < src->height; ++i) {
+        const quint16 *src_line = reinterpret_cast<const quint16 *>(src_data);
+        QRgba64 *dest_line = reinterpret_cast<QRgba64 *>(dest_data);
+        for (int j = 0; j < src->width; ++j) {
+            quint16 s = src_line[j];
+            dest_line[j] = qRgba64(s, s, s, 0xFFFF);
+        }
+        src_data += sbpl;
+        dest_data += dbpl;
+    }
+}
+
+static void convert_RGBA64_to_gray16(QImageData *dest, const QImageData *src, Qt::ImageConversionFlags)
+{
+    Q_ASSERT(dest->format == QImage::Format_Grayscale16);
+    Q_ASSERT(src->format == QImage::Format_RGBX64 ||
+             src->format == QImage::Format_RGBA64_Premultiplied);
+    Q_ASSERT(src->width == dest->width);
+    Q_ASSERT(src->height == dest->height);
+
+    const qsizetype sbpl = src->bytes_per_line;
+    const qsizetype dbpl = dest->bytes_per_line;
+    const uchar *src_data = src->data;
+    uchar *dest_data = dest->data;
+
+    for (int i = 0; i < src->height; ++i) {
+        const QRgba64 *src_line = reinterpret_cast<const QRgba64 *>(src_data);
+        quint16 *dest_line = reinterpret_cast<quint16 *>(dest_data);
+        for (int j = 0; j < src->width; ++j) {
+            QRgba64 s = src_line[j].unpremultiplied();
+            dest_line[j] = qGray(s.red(), s.green(), s.blue());
+        }
+        src_data += sbpl;
+        dest_data += dbpl;
+    }
+}
+
 static QVector<QRgb> fix_color_table(const QVector<QRgb> &ctbl, QImage::Format format)
 {
     QVector<QRgb> colorTable = ctbl;
@@ -2291,7 +2341,7 @@ static bool convert_Grayscale8_to_Indexed8_inplace(QImageData *data, Qt::ImageCo
 Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormats] =
 {
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     },
     {
         0,
@@ -2312,7 +2362,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_Mono
 
     {
@@ -2334,7 +2384,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_MonoLSB
 
     {
@@ -2359,7 +2409,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0, 0, 0, 0, 0,
         convert_Indexed8_to_Alpha8,
         convert_Indexed8_to_Grayscale8,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_Indexed8
 
     {
@@ -2387,7 +2437,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_RGB_to_RGB30<PixelOrderRGB, false>,
         0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_RGB32
 
     {
@@ -2417,7 +2467,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0, 0,
         0,
         convert_ARGB32_to_RGBA64<false>,
-        0
+        0, 0
     }, // Format_ARGB32
 
     {
@@ -2442,7 +2492,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_ARGB_to_RGBA,
         0, 0, 0, 0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     },  // Format_ARGB32_Premultiplied
 
     {
@@ -2464,7 +2514,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB16
 
     {
@@ -2486,7 +2536,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB8565_Premultiplied
 
     {
@@ -2508,7 +2558,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB666
 
     {
@@ -2530,7 +2580,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB6666_Premultiplied
 
     {
@@ -2552,7 +2602,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB555
 
     {
@@ -2574,7 +2624,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB8555_Premultiplied
 
     {
@@ -2597,7 +2647,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_RGB888_to_RGB<true>,
         convert_RGB888_to_RGB<true>,
         convert_RGB888_to_RGB<true>,
-        0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB888
 
     {
@@ -2619,7 +2669,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB444
 
     {
@@ -2640,7 +2690,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB4444_Premultiplied
     {
         0,
@@ -2667,7 +2717,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_RGB_to_RGB30<PixelOrderRGB, true>,
         0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_RGBX8888
     {
         0,
@@ -2696,7 +2746,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0, 0,
         0,
         convert_ARGB32_to_RGBA64<true>,
-        0
+        0, 0
     }, // Format_RGBA8888
 
     {
@@ -2718,7 +2768,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGBA8888_Premultiplied
 
     {
@@ -2746,7 +2796,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_BGR30_to_RGB30,
         convert_BGR30_to_RGB30,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_BGR30
     {
         0,
@@ -2773,8 +2823,8 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_A2RGB30_PM_to_RGB30<true>,
         convert_BGR30_to_RGB30,
         0, 0,
-        0, 0, 0
-    }, // Format_BGR30A2_Premultiplied
+        0, 0, 0, 0
+    }, // Format_A2BGR30_Premultiplied
     {
         0,
         0,
@@ -2799,7 +2849,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_BGR30_to_RGB30,
         0,
         convert_passthrough,
-        0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0
     }, // Format_RGB30
     {
         0,
@@ -2826,8 +2876,8 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         convert_A2RGB30_PM_to_RGB30<false>,
         0,
         0, 0,
-        0, 0, 0
-    }, // Format_RGB30A2_Premultiplied
+        0, 0, 0, 0
+    }, // Format_A2RGB30_Premultiplied
     {
         0,
         0,
@@ -2846,7 +2896,7 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_Alpha8
     {
         0,
@@ -2872,7 +2922,8 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, // self
         convert_passthrough,
-        convert_passthrough
+        convert_passthrough,
+        convert_RGBA64_to_gray16
     }, // Format_RGBX64
     {
         0,
@@ -2898,7 +2949,8 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0, 0,
         convert_RGBA64_to_RGBx64,
         0, // self
-        convert_RGBA64_to_RGBA64PM
+        convert_RGBA64_to_RGBA64PM,
+        0
     }, // Format_RGBA64
     {
         0,
@@ -2927,20 +2979,51 @@ Image_Converter qimage_converter_map[QImage::NImageFormats][QImage::NImageFormat
         0, 0,
         convert_RGBA64PM_to_RGBA64<true>,
         convert_RGBA64PM_to_RGBA64<false>,
-        0 // self
-    } // Format_RGBA64_Premultiplied
+        0, // self
+        convert_RGBA64_to_gray16
+    }, // Format_RGBA64_Premultiplied
+    {
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0, 0,
+        convert_gray16_to_RGBA64,
+        convert_gray16_to_RGBA64,
+        convert_gray16_to_RGBA64,
+        0  // self
+    }, // Format_Grayscale16
 };
 
 InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QImage::NImageFormats] =
 {
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     },
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_Mono
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_MonoLSB
     {
         0,
@@ -2964,7 +3047,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         0, 0, 0, 0, 0,
         convert_Indexed8_to_Alpha8_inplace,
         convert_Indexed8_to_Grayscale8_inplace,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_Indexed8
     {
         0,
@@ -2991,7 +3074,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_RGB_to_RGB30_inplace<PixelOrderRGB, false>,
         0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_RGB32
     {
         0,
@@ -3018,7 +3101,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_RGB_to_RGB30_inplace<PixelOrderRGB, false>,
         0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_ARGB32
     {
         0,
@@ -3042,34 +3125,34 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_ARGB_to_RGBA_inplace<QImage::Format_RGBA8888_Premultiplied>,
         0, 0, 0, 0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     },  // Format_ARGB32_Premultiplied
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB16
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB8565_Premultiplied
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB666
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB6666_Premultiplied
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB555
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB8555_Premultiplied
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB888
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGB444
     {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_ARGB4444_Premultiplied
     {
         0,
@@ -3096,7 +3179,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_RGB_to_RGB30_inplace<PixelOrderRGB, true>,
         0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_RGBX8888
     {
         0,
@@ -3123,7 +3206,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_RGB_to_RGB30_inplace<PixelOrderRGB, true>,
         0,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_RGBA8888
     {
         0,
@@ -3145,7 +3228,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         0,
         0,
         0,
-        0, 0, 0, 0, 0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0
     }, // Format_RGBA8888_Premultiplied
     {
         0,
@@ -3172,7 +3255,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_BGR30_to_RGB30_inplace,
         convert_BGR30_to_A2RGB30_inplace,
         0, 0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_BGR30
     {
         0,
@@ -3198,8 +3281,8 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         0, // self
         convert_A2RGB30_PM_to_RGB30_inplace<true>,
         convert_BGR30_to_RGB30_inplace,
-        0, 0, 0, 0, 0
-    }, // Format_BGR30A2_Premultiplied
+        0, 0, 0, 0, 0, 0
+    }, // Format_A2BGR30_Premultiplied
     {
         0,
         0,
@@ -3224,7 +3307,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_BGR30_to_A2RGB30_inplace,
         0, // self
         convert_passthrough_inplace<QImage::Format_A2RGB30_Premultiplied>,
-        0, 0, 0, 0, 0
+        0, 0, 0, 0, 0, 0
     }, // Format_RGB30
     {
         0,
@@ -3251,8 +3334,8 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         convert_A2RGB30_PM_to_RGB30_inplace<false>,
         0, // self
         0, 0,
-        0, 0, 0
-    }, // Format_RGB30A2_Premultiplied
+        0, 0, 0, 0
+    }, // Format_A2RGB30_Premultiplied
     {
         0,
         0,
@@ -3276,7 +3359,7 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         0, 0, 0, 0,
         0, // self
         0,
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_Alpha8
     {
         0,
@@ -3301,26 +3384,32 @@ InPlace_Image_Converter qimage_inplace_converter_map[QImage::NImageFormats][QIma
         0, 0, 0, 0,
         0,
         0, // self
-        0, 0, 0
+        0, 0, 0, 0
     }, // Format_Grayscale8
     {
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, // self
         convert_passthrough_inplace<QImage::Format_RGBA64>,
         convert_passthrough_inplace<QImage::Format_RGBA64_Premultiplied>,
+        0
     }, // Format_RGBX64
     {
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         convert_RGBA64_to_RGBx64_inplace,
         0, // self
-        convert_RGBA64_to_RGBA64PM_inplace
+        convert_RGBA64_to_RGBA64PM_inplace,
+        0
     }, // Format_RGBA64
     {
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         convert_RGBA64PM_to_RGBA64_inplace<true>,
         convert_RGBA64PM_to_RGBA64_inplace<false>,
-        0 // self
-    }  // Format_RGBA64_Premultiplied
+        0, // self
+        0
+    }, // Format_RGBA64_Premultiplied
+    {
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+    }, // Format_Grayscale16
 };
 
 static void qInitImageConversions()
diff --git a/src/gui/image/qimage_p.h b/src/gui/image/qimage_p.h
index e3a6c53833..de12a313e8 100644
--- a/src/gui/image/qimage_p.h
+++ b/src/gui/image/qimage_p.h
@@ -189,6 +189,7 @@ inline int qt_depthForFormat(QImage::Format format)
     case QImage::Format_RGB16:
     case QImage::Format_RGB444:
     case QImage::Format_ARGB4444_Premultiplied:
+    case QImage::Format_Grayscale16:
         depth = 16;
         break;
     case QImage::Format_RGB666:
diff --git a/src/gui/image/qpixmap_raster.cpp b/src/gui/image/qpixmap_raster.cpp
index 13c1c29d5b..2732bbd197 100644
--- a/src/gui/image/qpixmap_raster.cpp
+++ b/src/gui/image/qpixmap_raster.cpp
@@ -203,6 +203,9 @@ void QRasterPlatformPixmap::fill(const QColor &color)
         pixel = qAlpha(color.rgba());
     } else if (image.format() == QImage::Format_Grayscale8) {
         pixel = qGray(color.rgba());
+    } else if (image.format() == QImage::Format_Grayscale16) {
+        QRgba64 c = color.rgba64();
+        pixel = qGray(c.red(), c.green(), c.blue());
     } else
     {
         pixel = 0;
diff --git a/src/gui/image/qpnghandler.cpp b/src/gui/image/qpnghandler.cpp
index 8ae03d5d38..3655c39326 100644
--- a/src/gui/image/qpnghandler.cpp
+++ b/src/gui/image/qpnghandler.cpp
@@ -266,6 +266,18 @@ void setup_qt(QImage& image, png_structp png_ptr, png_infop info_ptr, QSize scal
                 else if (g == 1)
                     image.setColor(0, qRgba(255, 255, 255, 0));
             }
+        } else if (bit_depth == 16
+                   && png_get_channels(png_ptr, info_ptr) == 1
+                   && !png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
+            if (image.size() != QSize(width, height) || image.format() != QImage::Format_Grayscale16) {
+                image = QImage(width, height, QImage::Format_Grayscale16);
+                if (image.isNull())
+                    return;
+            }
+
+            png_read_update_info(png_ptr, info_ptr);
+            if (QSysInfo::ByteOrder == QSysInfo::LittleEndian)
+                png_set_swap(png_ptr);
         } else if (bit_depth == 16) {
             bool hasMask = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS);
             if (!hasMask)
@@ -687,7 +699,7 @@ QImage::Format QPngHandlerPrivate::readImageFormat()
             if (bit_depth == 1 && png_get_channels(png_ptr, info_ptr) == 1) {
                 format = QImage::Format_Mono;
             } else if (bit_depth == 16) {
-                format = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) ? QImage::Format_RGBA64 : QImage::Format_RGBX64;
+                format = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) ? QImage::Format_RGBA64 : QImage::Format_Grayscale16;
             } else if (bit_depth == 8 && !png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
                 format = QImage::Format_Grayscale8;
             } else {
@@ -861,7 +873,8 @@ bool QPNGImageWriter::writeImage(const QImage& image, volatile int compression_i
         else
             color_type = PNG_COLOR_TYPE_PALETTE;
     }
-    else if (image.format() == QImage::Format_Grayscale8)
+    else if (image.format() == QImage::Format_Grayscale8
+             || image.format() == QImage::Format_Grayscale16)
         color_type = PNG_COLOR_TYPE_GRAY;
     else if (image.hasAlphaChannel())
         color_type = PNG_COLOR_TYPE_RGB_ALPHA;
@@ -877,6 +890,7 @@ bool QPNGImageWriter::writeImage(const QImage& image, volatile int compression_i
     case QImage::Format_RGBX64:
     case QImage::Format_RGBA64:
     case QImage::Format_RGBA64_Premultiplied:
+    case QImage::Format_Grayscale16:
         bpc = 16;
         break;
     default:
@@ -988,6 +1002,7 @@ bool QPNGImageWriter::writeImage(const QImage& image, volatile int compression_i
         case QImage::Format_RGBX64:
         case QImage::Format_RGBA64:
         case QImage::Format_RGBA64_Premultiplied:
+        case QImage::Format_Grayscale16:
             png_set_swap(png_ptr);
             break;
         default:
@@ -1018,6 +1033,7 @@ bool QPNGImageWriter::writeImage(const QImage& image, volatile int compression_i
     case QImage::Format_MonoLSB:
     case QImage::Format_Indexed8:
     case QImage::Format_Grayscale8:
+    case QImage::Format_Grayscale16:
     case QImage::Format_RGB32:
     case QImage::Format_ARGB32:
     case QImage::Format_RGB888:
diff --git a/src/gui/opengl/qopenglpaintengine.cpp b/src/gui/opengl/qopenglpaintengine.cpp
index 001cb839fa..042b9ebd79 100644
--- a/src/gui/opengl/qopenglpaintengine.cpp
+++ b/src/gui/opengl/qopenglpaintengine.cpp
@@ -1574,14 +1574,15 @@ void QOpenGL2PaintEngineEx::drawImage(const QRectF& dest, const QImage& image, c
     case QImage::Format_Alpha8:
         if (ctx->functions()->hasOpenGLFeature(QOpenGLFunctions::TextureRGFormats)) {
             d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::AlphaImageSrc);
-            bindOption = QOpenGLTextureUploader::UseRedFor8BitBindOption;
+            bindOption = QOpenGLTextureUploader::UseRedForAlphaAndLuminanceBindOption;
         } else
             d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
         break;
     case QImage::Format_Grayscale8:
+    case QImage::Format_Grayscale16:
         if (ctx->functions()->hasOpenGLFeature(QOpenGLFunctions::TextureRGFormats)) {
             d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::GrayscaleImageSrc);
-            bindOption = QOpenGLTextureUploader::UseRedFor8BitBindOption;
+            bindOption = QOpenGLTextureUploader::UseRedForAlphaAndLuminanceBindOption;
         } else
             d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
         break;
diff --git a/src/gui/opengl/qopengltextureuploader.cpp b/src/gui/opengl/qopengltextureuploader.cpp
index 42e309b733..90253546c8 100644
--- a/src/gui/opengl/qopengltextureuploader.cpp
+++ b/src/gui/opengl/qopengltextureuploader.cpp
@@ -104,7 +104,7 @@ qsizetype QOpenGLTextureUploader::textureImage(GLenum target, const QImage &imag
     const bool isOpenGLES3orBetter = context->isOpenGLES() && context->format().majorVersion() >= 3;
     const bool sRgbBinding = (options & SRgbBindOption);
     Q_ASSERT(isOpenGL12orBetter || context->isOpenGLES());
-    Q_ASSERT((options & (SRgbBindOption | UseRedFor8BitBindOption)) != (SRgbBindOption | UseRedFor8BitBindOption));
+    Q_ASSERT((options & (SRgbBindOption | UseRedForAlphaAndLuminanceBindOption)) != (SRgbBindOption | UseRedForAlphaAndLuminanceBindOption));
 
     switch (image.format()) {
     case QImage::Format_RGB32:
@@ -213,7 +213,7 @@ qsizetype QOpenGLTextureUploader::textureImage(GLenum target, const QImage &imag
         if (sRgbBinding) {
             // Always needs conversion
             break;
-        } else if (options & UseRedFor8BitBindOption) {
+        } else if (options & UseRedForAlphaAndLuminanceBindOption) {
             externalFormat = internalFormat = GL_RED;
             pixelType = GL_UNSIGNED_BYTE;
             targetFormat = image.format();
@@ -223,7 +223,7 @@ qsizetype QOpenGLTextureUploader::textureImage(GLenum target, const QImage &imag
         if (sRgbBinding) {
             // Always needs conversion
             break;
-        } else if (options & UseRedFor8BitBindOption) {
+        } else if (options & UseRedForAlphaAndLuminanceBindOption) {
             externalFormat = internalFormat = GL_RED;
             pixelType = GL_UNSIGNED_BYTE;
             targetFormat = image.format();
@@ -243,7 +243,7 @@ qsizetype QOpenGLTextureUploader::textureImage(GLenum target, const QImage &imag
         if (sRgbBinding) {
             // Always needs conversion
             break;
-        } else if (options & UseRedFor8BitBindOption) {
+        } else if (options & UseRedForAlphaAndLuminanceBindOption) {
             externalFormat = internalFormat = GL_RED;
             pixelType = GL_UNSIGNED_BYTE;
             targetFormat = image.format();
@@ -259,6 +259,26 @@ qsizetype QOpenGLTextureUploader::textureImage(GLenum target, const QImage &imag
             targetFormat = image.format();
         }
         break;
+    case QImage::Format_Grayscale16:
+        if (sRgbBinding) {
+            // Always needs conversion
+            break;
+        } else if (options & UseRedForAlphaAndLuminanceBindOption) {
+            externalFormat = internalFormat = GL_RED;
+            pixelType = GL_UNSIGNED_SHORT;
+            targetFormat = image.format();
+        } else if (context->isOpenGLES() || context->format().profile() != QSurfaceFormat::CoreProfile) {
+            externalFormat = internalFormat = GL_LUMINANCE;
+            pixelType = GL_UNSIGNED_SHORT;
+            targetFormat = image.format();
+        } else if (funcs->hasOpenGLExtension(QOpenGLExtensions::TextureSwizzle)) {
+            GLint swizzle[4] = { GL_RED, GL_RED, GL_RED, GL_ONE };
+            funcs->glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_RGBA, swizzle);
+            externalFormat = internalFormat = GL_RED;
+            pixelType = GL_UNSIGNED_SHORT;
+            targetFormat = image.format();
+        }
+        break;
     default:
         break;
     }
diff --git a/src/gui/opengl/qopengltextureuploader_p.h b/src/gui/opengl/qopengltextureuploader_p.h
index d758b3787b..0dcf709d7e 100644
--- a/src/gui/opengl/qopengltextureuploader_p.h
+++ b/src/gui/opengl/qopengltextureuploader_p.h
@@ -65,7 +65,7 @@ public:
     enum BindOption {
         NoBindOption                            = 0x0000,
         PremultipliedAlphaBindOption            = 0x0001,
-        UseRedFor8BitBindOption                 = 0x0002,
+        UseRedForAlphaAndLuminanceBindOption    = 0x0002,
         SRgbBindOption                          = 0x0004,
         PowerOfTwoBindOption                    = 0x0008
     };
diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index 9ef210cc68..af9375fcec 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -857,6 +857,44 @@ static const QRgba64 *QT_FASTCALL fetchGrayscale8ToRGB64(QRgba64 *buffer, const
     return buffer;
 }
 
+static void QT_FASTCALL convertGrayscale16ToRGB32(uint *buffer, int count, const QVector<QRgb> *)
+{
+    for (int i = 0; i < count; ++i) {
+        const uint x = qt_div_257(buffer[i]);
+        buffer[i] = qRgb(x, x, x);
+    }
+}
+
+static const uint *QT_FASTCALL fetchGrayscale16ToRGB32(uint *buffer, const uchar *src, int index, int count,
+                                                      const QVector<QRgb> *, QDitherInfo *)
+{
+    const unsigned short *s = reinterpret_cast<const unsigned short *>(src) + index;
+    for (int i = 0; i < count; ++i) {
+        const uint x = qt_div_257(s[i]);
+        buffer[i] = qRgb(x, x, x);
+    }
+    return buffer;
+}
+
+static const QRgba64 *QT_FASTCALL convertGrayscale16ToRGBA64(QRgba64 *buffer, const uint *src, int count,
+                                                           const QVector<QRgb> *, QDitherInfo *)
+{
+    const unsigned short *s = reinterpret_cast<const unsigned short *>(src);
+    for (int i = 0; i < count; ++i)
+        buffer[i] = QRgba64::fromRgba64(s[i], s[i], s[i], 65535);
+    return buffer;
+}
+
+static const QRgba64 *QT_FASTCALL fetchGrayscale16ToRGBA64(QRgba64 *buffer, const uchar *src, int index, int count,
+                                                         const QVector<QRgb> *, QDitherInfo *)
+{
+    const unsigned short *s = reinterpret_cast<const unsigned short *>(src) + index;
+    for (int i = 0; i < count; ++i) {
+        buffer[i] = QRgba64::fromRgba64(s[i], s[i], s[i], 65535);
+    }
+    return buffer;
+}
+
 static void QT_FASTCALL storeARGB32FromARGB32PM(uchar *dest, const uint *src, int index, int count,
                                                 const QVector<QRgb> *, QDitherInfo *)
 {
@@ -1362,6 +1400,22 @@ static void QT_FASTCALL storeGrayscale8FromARGB32PM(uchar *dest, const uint *src
         dest[index + i] = qGray(qUnpremultiply(src[i]));
 }
 
+static void QT_FASTCALL storeGrayscale16FromRGB32(uchar *dest, const uint *src, int index, int count,
+                                                 const QVector<QRgb> *, QDitherInfo *)
+{
+    unsigned short *d = reinterpret_cast<unsigned short *>(dest) + index;
+    for (int i = 0; i < count; ++i)
+        d[i] = qGray(src[i]) * 257;
+}
+
+static void QT_FASTCALL storeGrayscale16FromARGB32PM(uchar *dest, const uint *src, int index, int count,
+                                                    const QVector<QRgb> *, QDitherInfo *)
+{
+    unsigned short *d = reinterpret_cast<unsigned short *>(dest) + index;
+    for (int i = 0; i < count; ++i)
+        d[i] = qGray(qUnpremultiply(src[i])) * 257;
+}
+
 static const uint *QT_FASTCALL fetchRGB64ToRGB32(uint *buffer, const uchar *src, int index, int count,
                                                  const QVector<QRgb> *, QDitherInfo *)
 {
@@ -1488,7 +1542,11 @@ QPixelLayout qPixelLayouts[QImage::NImageFormats] = {
     { true, true, QPixelLayout::BPP64, nullptr,
       convertPassThrough, nullptr,
       fetchRGB64ToRGB32, fetchPassThrough64,
-      storeRGB64FromRGB32, storeRGB64FromRGB32 } // Format_RGBA64_Premultiplied
+      storeRGB64FromRGB32, storeRGB64FromRGB32 }, // Format_RGBA64_Premultiplied
+    { false, false, QPixelLayout::BPP16, nullptr,
+      convertGrayscale16ToRGB32, convertGrayscale16ToRGBA64,
+      fetchGrayscale16ToRGB32, fetchGrayscale16ToRGBA64,
+      storeGrayscale16FromARGB32PM, storeGrayscale16FromRGB32 } // Format_Grayscale16
 };
 
 Q_STATIC_ASSERT(sizeof(qPixelLayouts) / sizeof(*qPixelLayouts) == QImage::NImageFormats);
@@ -1564,6 +1622,16 @@ static void QT_FASTCALL storeRGBA64PMFromRGBA64PM(uchar *dest, const QRgba64 *sr
         memcpy(d, src, count * sizeof(QRgba64));
 }
 
+static void QT_FASTCALL storeGray16FromRGBA64PM(uchar *dest, const QRgba64 *src, int index, int count,
+                                                const QVector<QRgb> *, QDitherInfo *)
+{
+    quint16 *d = reinterpret_cast<quint16*>(dest) + index;
+    for (int i = 0; i < count; ++i) {
+        QRgba64 s =  src[i].unpremultiplied();
+        d[i] = qGray(s.red(), s.green(), s.blue());
+    }
+}
+
 ConvertAndStorePixelsFunc64 qStoreFromRGBA64PM[QImage::NImageFormats] = {
     nullptr,
     nullptr,
@@ -1592,7 +1660,8 @@ ConvertAndStorePixelsFunc64 qStoreFromRGBA64PM[QImage::NImageFormats] = {
     storeGenericFromRGBA64PM<QImage::Format_Grayscale8>,
     storeRGBX64FromRGBA64PM,
     storeRGBA64FromRGBA64PM,
-    storeRGBA64PMFromRGBA64PM
+    storeRGBA64PMFromRGBA64PM,
+    storeGray16FromRGBA64PM
 };
 
 /*
@@ -1696,6 +1765,7 @@ static DestFetchProc destFetchProc[QImage::NImageFormats] =
     destFetch,          // Format_RGBX64
     destFetch,          // Format_RGBA64
     destFetch,          // Format_RGBA64_Premultiplied
+    destFetch,          // Format_Grayscale16
 };
 
 static DestFetchProc64 destFetchProc64[QImage::NImageFormats] =
@@ -1728,6 +1798,7 @@ static DestFetchProc64 destFetchProc64[QImage::NImageFormats] =
     destFetchRGB64,     // Format_RGBX64
     destFetch64,        // Format_RGBA64
     destFetchRGB64,     // Format_RGBA64_Premultiplied
+    destFetch64,        // Format_Grayscale16
 };
 
 /*
@@ -1881,6 +1952,7 @@ static DestStoreProc destStoreProc[QImage::NImageFormats] =
     destStore,          // Format_RGBX64
     destStore,          // Format_RGBA64
     destStore,          // Format_RGBA64_Premultiplied
+    destStore,          // Format_Grayscale16
 };
 
 static DestStoreProc64 destStoreProc64[QImage::NImageFormats] =
@@ -1912,7 +1984,8 @@ static DestStoreProc64 destStoreProc64[QImage::NImageFormats] =
     destStore64,        // Format_Grayscale8
     0,                  // Format_RGBX64
     destStore64RGBA64,  // Format_RGBA64
-    0                   // Format_RGBA64_Premultiplied
+    0,                  // Format_RGBA64_Premultiplied
+    destStore64,        // Format_Grayscale16
 };
 
 /*
@@ -3839,6 +3912,7 @@ static SourceFetchProc sourceFetchUntransformed[QImage::NImageFormats] = {
     fetchUntransformed,         // RGBX64
     fetchUntransformed,         // RGBA64
     fetchUntransformed,         // RGBA64_Premultiplied
+    fetchUntransformed,         // Grayscale16
 };
 
 static const SourceFetchProc sourceFetchGeneric[NBlendTypes] = {
@@ -5253,6 +5327,7 @@ void qBlendTexture(int count, const QSpan *spans, void *userData)
     case QImage::Format_RGBX64:
     case QImage::Format_RGBA64:
     case QImage::Format_RGBA64_Premultiplied:
+    case QImage::Format_Grayscale16:
         proc = processTextureSpansGeneric64[blendType];
         break;
     case QImage::Format_Invalid:
@@ -6259,6 +6334,14 @@ DrawHelper qDrawHelper[QImage::NImageFormats] =
         qt_alphargbblit_generic,
         qt_rectfill_quint64
     },
+    // Format_Grayscale16
+    {
+        blend_color_generic_rgb64,
+        0,
+        qt_alphamapblit_generic,
+        qt_alphargbblit_generic,
+        qt_rectfill_quint16
+    },
 };
 
 #if !defined(__SSE2__)
diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h
index 4dcfbc813b..37108949d6 100644
--- a/src/gui/painting/qdrawhelper_p.h
+++ b/src/gui/painting/qdrawhelper_p.h
@@ -879,6 +879,8 @@ static Q_ALWAYS_INLINE uint BYTE_MUL_RGB16_32(uint x, uint a) {
 
 // qt_div_255 is a fast rounded division by 255 using an approximation that is accurate for all positive 16-bit integers
 static Q_DECL_CONSTEXPR Q_ALWAYS_INLINE int qt_div_255(int x) { return (x + (x>>8) + 0x80) >> 8; }
+static Q_DECL_CONSTEXPR Q_ALWAYS_INLINE uint qt_div_257_floor(uint x) { return  (x - (x >> 8)) >> 8; }
+static Q_DECL_CONSTEXPR Q_ALWAYS_INLINE uint qt_div_257(uint x) { return qt_div_257_floor(x + 128); }
 static Q_DECL_CONSTEXPR Q_ALWAYS_INLINE uint qt_div_65535(uint x) { return (x + (x>>16) + 0x8000U) >> 16; }
 
 static Q_ALWAYS_INLINE uint qAlphaRgb30(uint c)
diff --git a/tests/auto/gui/image/qimage/tst_qimage.cpp b/tests/auto/gui/image/qimage/tst_qimage.cpp
index 5ffd75f931..2e2cb52b3e 100644
--- a/tests/auto/gui/image/qimage/tst_qimage.cpp
+++ b/tests/auto/gui/image/qimage/tst_qimage.cpp
@@ -298,6 +298,8 @@ static QLatin1String formatToString(QImage::Format format)
         return QLatin1String("RGBA64");
     case QImage::Format_RGBA64_Premultiplied:
         return QLatin1String("RGBA64pm");
+    case QImage::Format_Grayscale16:
+        return QLatin1String("Grayscale16");
     default:
         break;
     };
@@ -2366,8 +2368,11 @@ void tst_QImage::rgbSwapped_data()
     QTest::addColumn<QImage::Format>("format");
 
     for (int i = QImage::Format_Indexed8; i < QImage::NImageFormats; ++i) {
-        if (i == QImage::Format_Alpha8 || i == QImage::Format_Grayscale8)
+        if (i == QImage::Format_Alpha8
+            || i == QImage::Format_Grayscale8
+            || i == QImage::Format_Grayscale16) {
             continue;
+        }
         QTest::addRow("%s", formatToString(QImage::Format(i)).data()) << QImage::Format(i);
     }
 }
@@ -2612,8 +2617,11 @@ void tst_QImage::inplaceMirrored_data()
     QTest::addColumn<bool>("swap_horizontal");
 
     for (int i = QImage::Format_Mono; i < QImage::NImageFormats; ++i) {
-        if (i == QImage::Format_Alpha8 || i == QImage::Format_Grayscale8)
+        if (i == QImage::Format_Alpha8
+            || i == QImage::Format_Grayscale8
+            || i == QImage::Format_Grayscale16) {
             continue;
+        }
         if (i == QImage::Format_RGB444 || i == QImage::Format_ARGB4444_Premultiplied)
             continue;
         const auto fmt = formatToString(QImage::Format(i));
@@ -2785,11 +2793,11 @@ void tst_QImage::genericRgbConversion_data()
     QTest::addColumn<QImage::Format>("dest_format");
 
     for (int i = QImage::Format_RGB32; i < QImage::NImageFormats; ++i) {
-        if (i == QImage::Format_Alpha8 || i == QImage::Format_Grayscale8)
+        if (i == QImage::Format_Alpha8)
             continue;
         const QLatin1String formatI = formatToString(QImage::Format(i));
         for (int j = QImage::Format_RGB32; j < QImage::NImageFormats; ++j) {
-            if (j == QImage::Format_Alpha8 || j == QImage::Format_Grayscale8)
+            if (j == QImage::Format_Alpha8)
                 continue;
             if (i == j)
                 continue;
@@ -2805,6 +2813,9 @@ void tst_QImage::genericRgbConversion()
     QFETCH(QImage::Format, format);
     QFETCH(QImage::Format, dest_format);
 
+    bool srcGrayscale = format == QImage::Format_Grayscale8 || format == QImage::Format_Grayscale16;
+    bool dstGrayscale = dest_format == QImage::Format_Grayscale8 || dest_format == QImage::Format_Grayscale16;
+
     QImage image(16, 16, format);
 
     for (int i = 0; i < image.height(); ++i)
@@ -2816,8 +2827,12 @@ void tst_QImage::genericRgbConversion()
     for (int i = 0; i < imageConverted.height(); ++i) {
         for (int j = 0; j < imageConverted.width(); ++j) {
             QRgb convertedColor = imageConverted.pixel(j,i);
-            QCOMPARE(qRed(convertedColor) & 0xF0, j * 16);
-            QCOMPARE(qGreen(convertedColor) & 0xF0, i * 16);
+            if (srcGrayscale || dstGrayscale) {
+                QVERIFY(qAbs(qGray(convertedColor) - qGray(qRgb(j*16, i*16, 0))) < 15);
+            } else {
+                QCOMPARE(qRed(convertedColor) & 0xF0, j * 16);
+                QCOMPARE(qGreen(convertedColor) & 0xF0, i * 16);
+            }
         }
     }
 }
@@ -2828,11 +2843,17 @@ void tst_QImage::inplaceRgbConversion_data()
     QTest::addColumn<QImage::Format>("dest_format");
 
     for (int i = QImage::Format_RGB32; i < QImage::NImageFormats; ++i) {
-        if (i == QImage::Format_Alpha8 || i == QImage::Format_Grayscale8)
+        if (i == QImage::Format_Alpha8
+            || i == QImage::Format_Grayscale8
+            || i == QImage::Format_Grayscale16) {
             continue;
+        }
         for (int j = QImage::Format_RGB32; j < QImage::NImageFormats; ++j) {
-            if (j == QImage::Format_Alpha8 || j == QImage::Format_Grayscale8)
+            if (j == QImage::Format_Alpha8
+                || j == QImage::Format_Grayscale8
+                || j == QImage::Format_Grayscale16) {
                 continue;
+            }
             if (i == j)
                 continue;
             QTest::addRow("%s -> %s", formatToString(QImage::Format(i)).data(), formatToString(QImage::Format(j)).data())
@@ -3002,8 +3023,11 @@ void tst_QImage::invertPixelsRGB_data()
     QTest::addColumn<QImage::Format>("image_format");
 
     for (int i = QImage::Format_RGB32; i < QImage::NImageFormats; ++i) {
-        if (i == QImage::Format_Alpha8 || i == QImage::Format_Grayscale8)
+        if (i == QImage::Format_Alpha8
+            || i == QImage::Format_Grayscale8
+            || i == QImage::Format_Grayscale16) {
             continue;
+        }
         QTest::addRow("%s", formatToString(QImage::Format(i)).data()) << QImage::Format(i);
     }
 }
diff --git a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
index c2ec5b8925..1cf01133b2 100644
--- a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
+++ b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
@@ -525,7 +525,7 @@ void tst_QImageReader::imageFormat_data()
     QTest::newRow("png") << QString("kollada.png") << QByteArray("png") << QImage::Format_ARGB32;
     QTest::newRow("png-2") << QString("YCbCr_cmyk.png") << QByteArray("png") << QImage::Format_RGB32;
     QTest::newRow("png-3") << QString("kollada-16bpc.png") << QByteArray("png") << QImage::Format_RGBA64;
-    QTest::newRow("png-4") << QString("basn0g16.png") << QByteArray("png") << QImage::Format_RGBX64; // Grayscale16
+    QTest::newRow("png-4") << QString("basn0g16.png") << QByteArray("png") << QImage::Format_Grayscale16;
     QTest::newRow("png-5") << QString("basn2c16.png") << QByteArray("png") << QImage::Format_RGBX64;
     QTest::newRow("png-6") << QString("basn4a16.png") << QByteArray("png") << QImage::Format_RGBA64; // Grayscale16Alpha16
     QTest::newRow("png-7") << QString("basn6a16.png") << QByteArray("png") << QImage::Format_RGBA64;
diff --git a/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp b/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp
index 77851cd7d0..aaa8475c74 100644
--- a/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp
+++ b/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp
@@ -239,7 +239,7 @@ void tst_QImageWriter::writeImage2_data()
         // QLatin1String("jpeg"),
     };
 
-    QImage image0(70, 70, QImage::Format_ARGB32);
+    QImage image0(70, 70, QImage::Format_RGB32);
     image0.fill(QColor(Qt::red).rgb());
 
     QImage::Format imgFormat = QImage::Format_Mono;
@@ -304,10 +304,10 @@ void tst_QImageWriter::writeImage2()
     if (!equalImageContents(written, image)) {
         qDebug() << "image" << image.format() << image.width()
                  << image.height() << image.depth()
-                 << hex << image.pixel(0, 0);
+                 << image.pixelColor(0, 0);
         qDebug() << "written" << written.format() << written.width()
                  << written.height() << written.depth()
-                 << hex << written.pixel(0, 0);
+                 << written.pixelColor(0, 0);
     }
     QVERIFY(equalImageContents(written, image));