QPainter::drawLine(): straight lines look aliased

[xqrp]

I'm trying to draw two single pixel lines onto a QImage with the following code:

QPainter linePainter(currentImage);
linePainter.setRenderHint(QPainter::Antialiasing, false);
linePainter.setPen(QPen(Qt::red,1));
linePainter.drawLine(xSize/2, 0, xSize/2, ySize);
linePainter.drawLine(0, ySize/2, xSize, ySize/2);

QPainter linePainter(currentImage);
linePainter.setRenderHint(QPainter::Antialiasing, false);
linePainter.setPen(QPen(Qt::red,1));
linePainter.drawLine(xSize/2, 0, xSize/2, ySize);
linePainter.drawLine(0, ySize/2, xSize, ySize/2);

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The image is displayed on a QLabel like this:

ccdDisplayLabel->setPixmap(QPixmap::fromImage(*currentImage));

ccdDisplayLabel->setPixmap(QPixmap::fromImage(*currentImage));

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However, as you can see from the attached image, somewhere along the line something bad happens. The lines should be one pixel wide and bright red, however, the vertical line looks weird. How can I fix this?

CcdDialogCrosshairs.png