Render from a thread into a pixmap?

[rage]

I combine up to nine RGB-images with a resolution of 256x256 each to one large image. I want to do this depending on user interaction multiple times a second. The combined QImage is created in the "worker" thread and gets converted to a pixmap in the GUI thread (by calling QPixmap::fromImage()). Here I draw it on the screen. The conversion from QImage to QPixmap with a resolution of eg 768x768 is the slowest operation I think.

[wysota]

If you do it several times a second, I suggest you draw it to the screen without composing it first on an offscreen bitmap. Or even use OpenGL.

[rage]

If you do it several times a second, I suggest you draw it to the screen without composing it first on an offscreen bitmap. Or even use OpenGL.

Currently I am playing with the QCoreApplication::processEvents() you mentioned. I think this could solve my problem. I am not using OpenGL, bacause the application should also run on Qtopia devices...

[jacek]

The conversion from QImage to QPixmap with a resolution of eg 768x768 is the slowest operation I think.

It could be, but you have said that drawing on QImage is slower than drawing on QPixmap. Have you tried to use a profiler to check the times?

[rage]

I could be, but you have said that drawing on QImage is slower than drawing on QPixmap. Have you tried to use a profiler to check the times?

Yes, I have done that with callgrind. The fromImage() call takes ~44% of the processing time.

[rage]

Thanks wysota!
I'm now rendering the QPixmap within the GUI thread, so I don't need QImages. By calling processEvents() it doesn't block. I'll just have to do some locking with mutexes and then everything should be fine!

[longtrue]

How rendering the QPixmap within the GUI thread? And how to do it won't be block?Would you mind write your handle?Thanks

[faldzip]

Read this: http://doc.trolltech.com/qq/qq27-responsive-guis.html.