Dear Qt friends
I am no expert, but more or less familiar with Qt. But for my current task I don’t find the solution. And I already spend several days on browsing through documentations/examples etc. and tried a lot.
The application I want to develop: I have attached N=1..20 industrial cameras to my computer, each producing 25 frames/sec at a resolution of 2048×2048 (they provide raw uncoded images in RGB format). I am capturing the cameras in a background thread. And now I simply want to put the N images on each frame (at 25 FPS) on screen side-by-side in a tile/mosaic manner. Since I wrote the capturing background thread, I can adapt the data format or other things.
My current attempt is to setup a QGraphicsScene and QGraphicsView. But unfortunately, as it seems, on each frame update, I have to takeover each image by
(a) copying it into a QImage via QImage constructor,
(b) copy-scale it to 1/Nth of the screen-size via QImage::scaledToHeight() / QImage::scaledToWidth(),
© copy it into a QPixmap via QPixmap::convertFromImage()
(d) copy it into the scene via QGraphicsPixmapItem::setPixmap()
This is terribly slow and inefficient! I thought, there should be a way, to register a QImage to QGraphicsScene/QGraphicsView, so that it is always shown as I want it (in a tile besides others or full-screen, the whole image or only a zoomed part of it). And I thought, updating such a QImage with a newly captured camera frame should be easy, but I see no way for loading a new image into an existing QImage. Even better would be, to get access to the image memory inside QImage – in that way, I could convert the data directly from camera-native format into Qt-native format, without any unnecessary copying.
I am very happy about any feedback! Is my approach feasible? Are there other better ways? Do I have to change only a little detail or my complete thinking? Thanks a lot.
Best wishes,
Philipp
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