Fix printing of dpr>1 images on Windows

The win32 printing paint engine copies tiles of the source image into
temporary target images for printing. It does that using QPainter
painting. If there is a difference in DPR between source and target,
the painting will be scaled, leading to distorted results.

Fixes: QTBUG-99990
Pick-to: 6.4 6.3 6.2 5.15
Change-Id: Ie7368655ef3abeece49fb1a6421e2d6ea7ed5e95
Reviewed-by: André de la Rocha <andre.rocha@qt.io>

src/printsupport/platform/windows/qprintengine_win.cpp

@@ -563,6 +563,7 @@ void QWin32PrintEngine::drawPixmap(const QRectF &targetRect,
             QImage img(QSize(imgw, imgh), QImage::Format_RGB32);
             img.fill(Qt::white);
             QPainter painter(&img);
+            img.setDevicePixelRatio(pixmap.devicePixelRatio());
             painter.drawPixmap(0,0, pixmap, tileSize * x, tileSize * y, imgw, imgh);
             QPixmap p = QPixmap::fromImage(img);