Faster way to manage an image

[vinnzcrafts]

Good day people
I'm here to ask for your help on the following:
How can I manage an image in a faster way in Qt, or even plain C++ if this is possible at all.
Instead of creating a QGraphicsView with a QGraphicsScene and QGraphicsPixmapItem
and update it etc... I need a way where I could alter a pixel array and update it directly as if I was poking
inside the QGraphicsView drawing area directly... If Qt is not the tool to do that feel free to indicate
some framework or something in which I can do this.
I'm looking for this because I'm making a program with heavy graphics but not the kind of thing
that QPainter draws neither I need different graphics items, I just need to be able to use this giant
pixmap like an array and update the changes fast to the screen.
Thanks in advance