QPainter, QPixmap, drawPie and Transformations



  • I have a PNG image which I've loaded into my application as a QPixmap.

    What I'm looking to do is to stretch this image into the shape of a pie slice and draw it using the QPainter::drawPie function.

    Having loaded a new QBrush instance with the QPixmap, I now need to somehow transform the brush to the shape of the pie.

    Any clues as to how this may be achieved? Thank you in advance for any hints


  • Qt Champions 2017

    hi
    Hmm
    DrawPie will use any brush set to fill the pie.
    I assume you want it filled other than how brush does ?



  • @mrjj You are indeed correct - I want the brush to be transformed so that the QPixmap is adjusted to fill the interior of the pie, assuming the shape of the pie.


  • Qt Champions 2017

    @webzoid
    It does have
    void QBrush::setTransform(const QTransform & matrix)
    but its unclear how you mean it should be draw since
    it does brush does fill the interior but will do so in a reaping manner.



  • @mrjj Sorry, I'm not explaining this very well...

    Imagine the point of the pie slice. The bitmap should be drawn such that the pixels on the bottom row are squashed into this point. Then imagine the curve of the pie slice, the top row of the bitmap (and nearby pixels) would be stretched and transformed to fit in the curve.

    All other pixels within the bitmap would also be transformed to fill the remaining area of the pie slice.

    Does that make any sense at all :)


  • Qt Champions 2017

    @webzoid
    Hmm i think i get it now, like a perfect fit for the pixmap
    and not just filled as repeating fill.
    Something like
    https://stackoverflow.com/questions/30980484/qt-fill-circle-with-images
    ?


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