Planned maintenance has been done but it did not solve the problem. So work will continue on this and a new time for trying updates will be announced asap.

Artefacts in QImage on Mac OS X



  • Hi all,

    I see strange artefacts in a QImage when lines are drawn on a light background. A screen shot is here: http://www.mynetcologne.de/~nc-dreszal/qt_macosx_artefacts.png - note that brown lines on green bg look fine...

    The effect occurs in QLandkarte GT [1] on Mac OS X 10.5, and seems not to be related to the type of graphics card used (both ATI and NVIDIA show the issue). Also, no user reported a similar problem for the Linux or for the Windows versions of the application. On my old PowerMac G4 running Mac OS X 10.4 (ATI graphics), the graphics looks also fine. I didn't receive and complaints from users running Mac OS X 10.6, so it may or may not work properly there.

    The underlying Qt version used for the Mac version is 4.6.3 on all systems. The code used to draw the image is basically (quoting the application's author, "buffer" is a QImage):

    @
    void CMapTDB::draw()
    {
    buffer.fill(Qt::transparent);
    QPainter p(&buffer);
    [...]
    USE_ANTI_ALIASING(p,!doFastDraw && CResources::self().useAntiAliasing());
    [...]
    }
    @

    Any help to fix this bug would be appreciated!

    Best,
    Albrecht.

    [1] http://www.qlandkarte.org/

    [EDIT: fixed code formatting, pleas use @-tags, Volker]


  • Moderators

    The first step to get a bug fixed would of course be to report it in the "Qt bug tracker":http://bugreports.qt.nokia.com/.

    Some sample application or test case is always appreciated as it makes working on the issue so much easier.


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