No fluid image with QGraphicView and QGraphicScene

[spud]

mScene->addPixmap(QPixmap::fromImage(IplImageToQImage(img)));

mScene->addPixmap(QPixmap::fromImage(IplImageToQImage(img)));

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You should only call addPixmap() once. Otherwise all the previous frames remain in the scene behind the current frame.
Keep a reference instead:

// Do once:
 QGraphicsPixmapItem* pixItem = mScene->addPixmap(QPixmap::fromImage(IplImageToQImage(img))); 
 
 
// Update:
pixItem->setPixmap(QPixmap::fromImage(IplImageToQImage(img)));

// Do once:
 QGraphicsPixmapItem* pixItem = mScene->addPixmap(QPixmap::fromImage(IplImageToQImage(img))); 


// Update:
pixItem->setPixmap(QPixmap::fromImage(IplImageToQImage(img)));

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No need to call update(). The item takes care of that for itself.