QtGui: Add Windows conversion functions for to QImage

Add conversions from/to HBITMAP, HICON to QImage. Split the pixmap
conversion functions apart to use them.

Task-number: QTBUG-81876
Change-Id: Ic0c41a402a1f6e9bec572fc4d691357bd48e6423
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/image/qimage.h

@@ -298,6 +298,11 @@ public:
     // Platform specific conversion functions
 #if defined(Q_OS_DARWIN) || defined(Q_QDOC)
     CGImageRef toCGImage() const Q_DECL_CF_RETURNS_RETAINED;
+#elif defined(Q_OS_WIN) || defined(Q_QDOC)
+    HBITMAP toHBITMAP() const;
+    HICON toHICON(const QImage &mask = {}) const;
+    static QImage fromHBITMAP(HBITMAP hbitmap);
+    static QImage fromHICON(HICON icon);
 #endif
 
 protected:

src/gui/image/qpixmap_win.cpp

@@ -228,9 +228,9 @@ enum HBitmapFormat
     HBitmapAlpha
 };
 
-Q_GUI_EXPORT HBITMAP qt_createIconMask(const QBitmap &bitmap)
+static HBITMAP qt_createIconMask(QImage bm)
 {
-    QImage bm = bitmap.toImage().convertToFormat(QImage::Format_Mono);
+    Q_ASSERT(bm.format() == QImage::Format_Mono);
     const int w = bm.width();
     const int h = bm.height();
     const int bpl = ((w+15)/16)*2; // bpl, 16 bit alignment
@@ -242,6 +242,11 @@ Q_GUI_EXPORT HBITMAP qt_createIconMask(const QBitmap &bitmap)
     return hbm;
 }
 
+Q_GUI_EXPORT HBITMAP qt_createIconMask(const QBitmap &bitmap)
+{
+    return qt_createIconMask(bitmap.toImage().convertToFormat(QImage::Format_Mono));
+}
+
 static inline QImage::Format format32(int hbitmapFormat)
 {
     switch (hbitmapFormat) {
@@ -344,6 +349,40 @@ Q_GUI_EXPORT HBITMAP qt_imageToWinHBITMAP(const QImage &imageIn, int hbitmapForm
     return bitmap;
 }
 
+/*!
+    \since 6.0
+
+    Creates a \c HBITMAP equivalent of the QImage. Returns the \c HBITMAP
+    handle.
+
+    It is the caller's responsibility to free the \c HBITMAP data
+    after use.
+
+    For usage with with standard GDI calls, such as \c BitBlt(), the image
+    should have the format QImage::Format_RGB32.
+
+    When using the resulting HBITMAP for the \c AlphaBlend() GDI function,
+    the image should have the format QImage::Format_ARGB32_Premultiplied
+    (use convertToFormat()).
+
+    When using the resulting HBITMAP as application icon or a systray icon,
+    the image should have the format QImage::Format_ARGB32.
+
+    \sa fromHBITMAP(), convertToFormat()
+*/
+HBITMAP QImage::toHBITMAP() const
+{
+    switch (format()) {
+    case QImage::Format_ARGB32:
+        return qt_imageToWinHBITMAP(*this, HBitmapAlpha);
+    case QImage::Format_ARGB32_Premultiplied:
+        return qt_imageToWinHBITMAP(*this, HBitmapPremultipliedAlpha);
+    default:
+        break;
+    }
+    return qt_imageToWinHBITMAP(*this);
+}
+
 Q_GUI_EXPORT HBITMAP qt_pixmapToWinHBITMAP(const QPixmap &p, int hbitmapFormat = 0)
 {
     if (p.isNull())
@@ -451,26 +490,64 @@ Q_GUI_EXPORT QImage qt_imageFromWinHBITMAP(HBITMAP bitmap, int hbitmapFormat = 0
     return result;
 }
 
+/*!
+    \since 6.0
+
+    Returns a QImage that is equivalent to the given \a bitmap.
+
+    HBITMAP does not store information about the alpha channel.
+
+    In the standard case, the alpha channel is ignored and a fully
+    opaque image is created (typically of format QImage::Format_RGB32).
+
+    There are cases where the alpha channel is used, though, for example
+    for application icon or systray icons. In that case,
+    \c reinterpretAsFormat(QImage::Format_ARGB32) should be called
+    on the returned image to ensure the format is correct.
+
+    \sa toHBITMAP(), reinterpretAsFormat()
+*/
+QImage QImage::fromHBITMAP(HBITMAP hbitmap)
+{
+    return qt_imageFromWinHBITMAP(hbitmap);
+}
+
 Q_GUI_EXPORT QPixmap qt_pixmapFromWinHBITMAP(HBITMAP bitmap, int hbitmapFormat = 0)
 {
     return QPixmap::fromImage(imageFromWinHBITMAP_GetDiBits(bitmap, /* forceQuads */ true, hbitmapFormat));
 }
 
-Q_GUI_EXPORT HICON qt_pixmapToWinHICON(const QPixmap &p)
+/*!
+    \since 6.0
+
+    Creates a \c HICON equivalent of the QPixmap, applying the mask
+    \a mask. If \a mask is not null, it needs to be of format QImage::Format_Mono.
+    Returns the \c HICON handle.
+
+    It is the caller's responsibility to free the \c HICON data after use.
+
+    \sa fromHICON()
+*/
+HICON QImage::toHICON(const QImage &mask) const
 {
-    if (p.isNull())
+    if (!mask.isNull() && mask.format() != QImage::Format_Mono) {
+        qWarning("QImage::toHICON(): Mask must be empty or have format Format_Mono");
+        return nullptr;
+    }
+
+    if (isNull())
         return nullptr;
 
-    QBitmap maskBitmap = p.mask();
+    auto effectiveMask = mask;
-    if (maskBitmap.isNull()) {
+    if (effectiveMask.isNull()) {
-        maskBitmap = QBitmap(p.size());
+        effectiveMask = QImage(size(), QImage::Format_Mono);
-        maskBitmap.fill(Qt::color1);
+        effectiveMask.fill(Qt::color1);
     }
 
     ICONINFO ii;
     ii.fIcon    = true;
-    ii.hbmMask  = qt_createIconMask(maskBitmap);
+    ii.hbmMask  = qt_createIconMask(effectiveMask);
-    ii.hbmColor = qt_pixmapToWinHBITMAP(p, HBitmapAlpha);
+    ii.hbmColor = qt_imageToWinHBITMAP(*this, HBitmapAlpha);
     ii.xHotspot = 0;
     ii.yHotspot = 0;
 
@@ -482,6 +559,15 @@ Q_GUI_EXPORT HICON qt_pixmapToWinHICON(const QPixmap &p)
     return hIcon;
 }
 
+Q_GUI_EXPORT HICON qt_pixmapToWinHICON(const QPixmap &p)
+{
+    QImage mask;
+    QBitmap maskBitmap = p.mask();
+    if (!maskBitmap.isNull())
+        mask = maskBitmap.toImage().convertToFormat(QImage::Format_Mono);
+    return p.toImage().toHICON(mask);
+}
+
 Q_GUI_EXPORT QImage qt_imageFromWinHBITMAP(HDC hdc, HBITMAP bitmap, int w, int h)
 {
     QImage image(w, h, QImage::Format_ARGB32_Premultiplied);
@@ -520,7 +606,14 @@ static inline bool hasAlpha(const QImage &image)
     return false;
 }
 
-Q_GUI_EXPORT QPixmap qt_pixmapFromWinHICON(HICON icon)
+/*!
+    \since 6.0
+
+    Returns a QImage that is equivalent to the given \a icon.
+
+    \sa toHICON()
+*/
+QImage QImage::fromHICON(HICON icon)
 {
     HDC screenDevice = GetDC(nullptr);
     HDC hdc = CreateCompatibleDC(screenDevice);
@@ -531,7 +624,7 @@ Q_GUI_EXPORT QPixmap qt_pixmapFromWinHICON(HICON icon)
     if (!result) {
         qErrnoWarning("QPixmap::fromWinHICON(), failed to GetIconInfo()");
         DeleteDC(hdc);
-        return QPixmap();
+        return {};
     }
 
     const int w = int(iconinfo.xHotspot) * 2;
@@ -570,7 +663,12 @@ Q_GUI_EXPORT QPixmap qt_pixmapFromWinHICON(HICON icon)
     SelectObject(hdc, oldhdc); //restore state
     DeleteObject(winBitmap);
     DeleteDC(hdc);
-    return QPixmap::fromImage(std::move(image));
+    return image;
+}
+
+Q_GUI_EXPORT QPixmap qt_pixmapFromWinHICON(HICON icon)
+{
+    return QPixmap::fromImage(QImage::fromHICON(icon));
 }
 
 QT_END_NAMESPACE

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

@@ -3777,10 +3777,6 @@ void tst_QImage::wideImage()
 }
 
 #if defined(Q_OS_WIN)
-QT_BEGIN_NAMESPACE
-Q_GUI_EXPORT HBITMAP qt_imageToWinHBITMAP(const QImage &p, int hbitmapFormat = 0);
-Q_GUI_EXPORT QImage qt_imageFromWinHBITMAP(HBITMAP bitmap, int hbitmapFormat = 0);
-QT_END_NAMESPACE
 
 static inline QColor COLORREFToQColor(COLORREF cr)
 {
@@ -3844,7 +3840,7 @@ void tst_QImage::toWinHBITMAP()
         ? createTestImage(QImage::Format_RGB32, width, height, color, bottomRightColor).convertToFormat(format)
         : createTestImage(format, width, height, color, bottomRightColor);
 
-    const HBITMAP bitmap = qt_imageToWinHBITMAP(image);
+    const HBITMAP bitmap = image.toHBITMAP();
 
     QVERIFY(bitmap != 0);
 
@@ -3867,7 +3863,7 @@ void tst_QImage::toWinHBITMAP()
     QCOMPARE(COLORREFToQColor(GetPixel(bitmapDc, 3, height - 1)), color);
     QCOMPARE(COLORREFToQColor(GetPixel(bitmapDc, width - 1, height - 1)), bottomRightColor);
 
-    const QImage convertedBack = qt_imageFromWinHBITMAP(bitmap);
+    const QImage convertedBack = QImage::fromHBITMAP(bitmap);
     QCOMPARE(convertedBack.convertToFormat(QImage::Format_ARGB32_Premultiplied),
              image.convertToFormat(QImage::Format_ARGB32_Premultiplied));
 
@@ -3884,7 +3880,7 @@ void tst_QImage::fromMonoHBITMAP() // QTBUG-72343, corruption for mono bitmaps
     char bitmapData[size];
     memset(bitmapData, 0, size);
     const HBITMAP hbitmap  = CreateBitmap(width, height, /* planes */ 1, /* bitcount */ 1, bitmapData);
-    const QImage image = qt_imageFromWinHBITMAP(hbitmap);
+    const QImage image = QImage::fromHBITMAP(hbitmap);
     QCOMPARE(image.size(), QSize(width, height));
     QCOMPARE(image.scanLine(0)[0], 0u);
     DeleteObject(hbitmap);