QPixmap seems to be null but it isn't

[wysota]

If I use it in the costructor of the thread I haven't problems.

That's because the constructor of the QThread object is executed in the context of the main thread and not the worker thread that is not yet running.

[satoshi]

first of all, as I said, you can use GUI in a thread and QPixmap also.
use signals/slots or custom event for communication between threads.
read more about multithreading in Qt.

Thank you, that helped. Problem solved

That's because the constructor of the QThread object is executed in the context of the main thread and not the worker thread that is not yet running.

I know, my problem was that I wasn't understanding why it wasn't working in multi-threading...

Thank you! Dario