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Thread: QPixmap/QImage serious issues between Windows/Unix

  1. #1
    Join Date
    Nov 2011
    Posts
    2
    Qt products
    Qt4 Qt/Embedded
    Platforms
    Unix/X11 Windows

    Question QPixmap/QImage serious issues between Windows/Unix

    Good day to you all around,

    I am writing a program which computes data and presents this data to the user. I am developing this program with Virtual Studio 10, but I also want to run the application on a Unix system. The problems I am experiencing are very frustrating. I hope you can help me on this.

    General architecture:
    Data ia read and processed in one thread, every computed frame of data is packed in a list as a QImage and a signal is fired up. The images are very big.
    When the signal is fetched, the QImage is transformed into a QPixmap and added to a QGraphicsScene. The user can see the scene through a QGraphicsView. I am experiencing some serious instability (an exception is thrown) when I close the application with the [x], but not when I close it with a specially tailored [Quit] button. Ideas on that? Bad architecture?

    The situation on Windows:
    The graphics are fast, but are not very nice. I found some nice flags I want to try out (QPainter, setRenderHints,..) but I haven't found the entry point for that. Anyway, in general: Windows works and is fast. Rest is cosmetics.

    The same code on Unix:
    Slow as hell. I read on the forums and on the QtLabs blog that this may come from the conversion between QImage and QPixmap. With Raster as the graphicssystem I see the incoming data rather fast, but painting on the scene is still hellish slow. Also, while the application produces grayscale images, on Unix everything is rainbow colored. I am not sure, but is it possible that Qt interprets my 8-Bit grayscales as RGB? I have set the flag for the format (8Bit Indexed). Priority target: Getting the image in grayscale without much overhead.
    Another issue: After some blocks of data a single white line is inserted. This only occurs under unix. And I have no clue why.

    Any help or direction advise would be helpful. Thanks in advance!

    edit: oh, its all in C/C++.

  2. #2
    Join Date
    Nov 2011
    Posts
    2
    Qt products
    Qt4 Qt/Embedded
    Platforms
    Unix/X11 Windows

    Default Re: QPixmap/QImage serious issues between Windows/Unix

    Okay, I fixed the error when closing the application by myself, but I am still experiencing the errors on the Unix environment. Any tips on that topic?
    Last edited by Largo; 22nd November 2011 at 14:22. Reason: typo

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