QImage -> QPixmap Issues all white on display

[wysota]

I will repeat my unanswered questions then:

• How do you run this method?
• So you got rid of all the threads?

[IanC]

Gotha, somehow I must have missed those original questions.
- In this code yes everything is running on the main GUI thread (for solving this problem). The code which collects up the UDP packets into a frame runs on a separate thread and sends a signal that the frame is complete with an index of the frame inside the buffer pool.
- When the slot is received (on the main GUI thread, I verified this with the debugger, and there are no messages that the QPixmap can't be used on the non gui thread) it calls a method to get the address of the buffer and the length (yes they are protected by a mutex), it then calls the routine which i provided a snippet from. When this routine finishes the caller release the buffer so the secondary thread can reuse it.

I just tried something else today. After I load the QImage from the buffer I call QImge.isNull() which returns false. After I convert the QImage to the QPixmap I call QPixmap.isNull() and it returns true. So something is going wrong with that conversion, even through QPixmap.fromImage() is returning true.

[IanC]

I figured out what the problem was. Somehow I didn't see that fromImage was a static member so my code was bogus
my_pixmap.fromImage(image); should have been my_pixmap = QPixmap::fromImage(image);

[Spitfire]

I wonder why do you use QImage as a temporary data container?
Wouldn't it be easier and faster to use QByteArray to store the data and load it directly to QPixmap?

[IanC]

Because my original goal was to do the JPEG decoding on a secondary thread. QPixmap cannot run on a secondary thread but QImage can. Therefore I load (which does the decode) QImage on the secondary thread, then let QPixmap render the image on the GUI thread.