Fix alpha handling of QImage::setPixel

It was treated differently depending on format, made it consistently
behave the same for all formats (following the behavior of the primary
formats).

Pick-to: 6.1 6.0 5.15
Change-Id: Ie24e19957d076fdf3ebd333074e26ede187489eb
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

src/gui/image/qimage.cpp

@@ -2486,7 +2486,7 @@ void QImage::setPixel(int x, int y, uint index_or_rgb)
         ((uint *)s)[x] = index_or_rgb;
         return;
     case Format_RGB16:
-        ((quint16 *)s)[x] = qConvertRgb32To16(qUnpremultiply(index_or_rgb));
+        ((quint16 *)s)[x] = qConvertRgb32To16(index_or_rgb);
         return;
     case Format_RGBX8888:
         ((uint *)s)[x] = ARGB2RGBA(0xff000000 | index_or_rgb);
@@ -2507,6 +2507,10 @@ void QImage::setPixel(int x, int y, uint index_or_rgb)
     case Format_A2RGB30_Premultiplied:
         ((uint *)s)[x] = qConvertArgb32ToA2rgb30<PixelOrderRGB>(index_or_rgb);
         return;
+    case Format_RGBA64:
+    case Format_RGBA64_Premultiplied:
+        ((QRgba64 *)s)[x] = QRgba64::fromArgb32(index_or_rgb);
+        return;
     case Format_Invalid:
     case NImageFormats:
         Q_ASSERT(false);
@@ -2516,6 +2520,9 @@ void QImage::setPixel(int x, int y, uint index_or_rgb)
     }
 
     const QPixelLayout *layout = &qPixelLayouts[d->format];
+    if (!hasAlphaChannel())
+        layout->storeFromRGB32(s, &index_or_rgb, x, 1, nullptr, nullptr);
+    else
         layout->storeFromARGB32PM(s, &index_or_rgb, x, 1, nullptr, nullptr);
 }
 

src/gui/painting/qpixellayout.cpp

@@ -1333,7 +1333,7 @@ static void QT_FASTCALL storeRGB64FromRGB32(uchar *dest, const uint *src, int in
 {
     QRgba64 *d = reinterpret_cast<QRgba64 *>(dest) + index;
     for (int i = 0; i < count; ++i)
-        d[i] = QRgba64::fromArgb32(src[i]);
+        d[i] = QRgba64::fromArgb32(src[i] | 0xff000000);
 }
 
 static const uint *QT_FASTCALL fetchRGBA64ToARGB32PM(uint *buffer, const uchar *src, int index, int count,
@@ -1345,12 +1345,24 @@ static const uint *QT_FASTCALL fetchRGBA64ToARGB32PM(uint *buffer, const uchar *
     return buffer;
 }
 
+template<bool Mask>
 static void QT_FASTCALL storeRGBA64FromARGB32PM(uchar *dest, const uint *src, int index, int count,
                                                 const QList<QRgb> *, QDitherInfo *)
 {
     QRgba64 *d = reinterpret_cast<QRgba64 *>(dest) + index;
-    for (int i = 0; i < count; ++i)
+    for (int i = 0; i < count; ++i) {
         d[i] = QRgba64::fromArgb32(src[i]).unpremultiplied();
+        if (Mask)
+            d[i].setAlpha(65535);
+    }
+}
+
+static void QT_FASTCALL storeRGBA64FromARGB32(uchar *dest, const uint *src, int index, int count,
+                                              const QList<QRgb> *, QDitherInfo *)
+{
+    QRgba64 *d = reinterpret_cast<QRgba64 *>(dest) + index;
+    for (int i = 0; i < count; ++i)
+        d[i] = QRgba64::fromArgb32(src[i]);
 }
 
 // Note:
@@ -1437,15 +1449,15 @@ QPixelLayout qPixelLayouts[QImage::NImageFormats] = {
     { false, false, QPixelLayout::BPP64, rbSwap_4x16,
       convertPassThrough, nullptr,
       fetchRGB64ToRGB32, fetchPassThrough64,
-      storeRGB64FromRGB32, storeRGB64FromRGB32 }, // Format_RGBX64
+      storeRGBA64FromARGB32PM<true>, storeRGB64FromRGB32 }, // Format_RGBX64
     { true, false, QPixelLayout::BPP64, rbSwap_4x16,
       convertARGB32ToARGB32PM, nullptr,
       fetchRGBA64ToARGB32PM, fetchRGBA64ToRGBA64PM,
-      storeRGBA64FromARGB32PM, storeRGB64FromRGB32 }, // Format_RGBA64
+      storeRGBA64FromARGB32PM<false>, storeRGB64FromRGB32 }, // Format_RGBA64
     { true, true, QPixelLayout::BPP64, rbSwap_4x16,
       convertPassThrough, nullptr,
       fetchRGB64ToRGB32, fetchPassThrough64,
-      storeRGB64FromRGB32, storeRGB64FromRGB32 }, // Format_RGBA64_Premultiplied
+      storeRGBA64FromARGB32, storeRGB64FromRGB32 }, // Format_RGBA64_Premultiplied
     { false, false, QPixelLayout::BPP16, nullptr,
       convertGrayscale16ToRGB32, convertGrayscale16ToRGBA64,
       fetchGrayscale16ToRGB32, fetchGrayscale16ToRGBA64,

tests/auto/gui/image/qimage/tst_qimage.cpp

@@ -102,6 +102,10 @@ private slots:
 
     void setPixel_data();
     void setPixel();
+    void setPixelWithAlpha_data();
+    void setPixelWithAlpha();
+    void setPixelColorWithAlpha_data();
+    void setPixelColorWithAlpha();
 
     void defaultColorTable_data();
     void defaultColorTable();
@@ -1457,6 +1461,62 @@ void tst_QImage::setPixel()
     }
 }
 
+void tst_QImage::setPixelWithAlpha_data()
+{
+    QTest::addColumn<QImage::Format>("format");
+
+    for (int c = QImage::Format_RGB32; c < QImage::NImageFormats; ++c) {
+        if (c == QImage::Format_Grayscale8)
+            continue;
+        if (c == QImage::Format_Grayscale16)
+            continue;
+        if (c == QImage::Format_Alpha8)
+            continue;
+        QTest::newRow(qPrintable(formatToString(QImage::Format(c)))) << QImage::Format(c);
+    }
+}
+
+void tst_QImage::setPixelWithAlpha()
+{
+    QFETCH(QImage::Format, format);
+    QImage image(1, 1, format);
+    QRgb referenceColor = qRgba(0, 170, 85, 170);
+    image.setPixel(0, 0, referenceColor);
+
+    if (!image.hasAlphaChannel())
+        referenceColor = 0xff000000 | referenceColor;
+
+    QRgb color = image.pixel(0, 0);
+    QCOMPARE(qRed(color) & 0xf0, qRed(referenceColor) & 0xf0);
+    QCOMPARE(qGreen(color) & 0xf0, qGreen(referenceColor) & 0xf0);
+    QCOMPARE(qBlue(color) & 0xf0, qBlue(referenceColor) & 0xf0);
+    QCOMPARE(qAlpha(color) & 0xf0, qAlpha(referenceColor) & 0xf0);
+}
+
+void tst_QImage::setPixelColorWithAlpha_data()
+{
+    setPixelWithAlpha_data();
+}
+
+void tst_QImage::setPixelColorWithAlpha()
+{
+    QFETCH(QImage::Format, format);
+    QImage image(1, 1, format);
+    image.setPixelColor(0, 0, QColor(170, 85, 255, 170));
+    QRgb referenceColor = qRgba(170, 85, 255, 170);
+
+    if (!image.hasAlphaChannel())
+        referenceColor = 0xff000000 | referenceColor;
+    else if (image.pixelFormat().premultiplied() == QPixelFormat::Premultiplied)
+        referenceColor = qPremultiply(referenceColor);
+
+    QRgb color = image.pixel(0, 0);
+    QCOMPARE(qRed(color) & 0xf0, qRed(referenceColor) & 0xf0);
+    QCOMPARE(qGreen(color) & 0xf0, qGreen(referenceColor) & 0xf0);
+    QCOMPARE(qBlue(color) & 0xf0, qBlue(referenceColor) & 0xf0);
+    QCOMPARE(qAlpha(color) & 0xf0, qAlpha(referenceColor) & 0xf0);
+}
+
 void tst_QImage::convertToFormatPreserveDotsPrMeter()
 {
     QImage img(100, 100, QImage::Format_ARGB32_Premultiplied);
@@ -2352,17 +2412,7 @@ void tst_QImage::fillColor()
 
 void tst_QImage::fillColorWithAlpha_data()
 {
-    QTest::addColumn<QImage::Format>("format");
+    setPixelWithAlpha_data();
-
-    for (int c = QImage::Format_RGB32; c < QImage::NImageFormats; ++c) {
-        if (c == QImage::Format_Grayscale8)
-            continue;
-        if (c == QImage::Format_Grayscale16)
-            continue;
-        if (c == QImage::Format_Alpha8)
-            continue;
-        QTest::newRow(qPrintable(formatToString(QImage::Format(c)))) << QImage::Format(c);
-    }
 }
 
 void tst_QImage::fillColorWithAlpha()