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Thread: QwtScaleWidget: problem with drawing a ColorMap

  1. #1
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    Question QwtScaleWidget: problem with drawing a ColorMap

    The problem I am having is that whenever I create and then draw a QwtScaleWidget with my defined color map it doesn't render properly. If I give it a range of 0 - 1 it renders fine but when ever I hand it any other range it does not render properly.

    I have listed my code below and some sample screenshots.

    Thanks for your time,
    Jon Jones

    Qt Code:
    1. QwtLinearColorMap colorMap(Qt::darkBlue, Qt::red);
    2. colorMap.addColorStop(0.25, Qt::cyan);
    3. colorMap.addColorStop(0.75, Qt::yellow);
    4.  
    5. QWidget *widget = canvas();
    6.  
    7. QwtScaleWidget *colorBar = new QwtScaleWidget(widget);
    8. colorBar->setColorMap(QwtDoubleInterval(0, 10), colorMap);
    9. colorBar->setColorBarEnabled(true);
    10. colorBar->drawColorBar(&painter, QRect(10,10, 25, 100));
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  2. #2
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    Default Re: QwtScaleWidget: problem with drawing a ColorMap

    Assuming you want to use the right axis for your color bar:

    Qt Code:
    1. QwtDoubleInterval range(0, 10);
    2.  
    3. QwtScaleWidget *scale = plot->axisWidget(QwtPlot::yRight);
    4. scale->setColorBarEnabled(true);
    5. scale->setColorMap(range, colorMap);
    6.  
    7. plot->setAxisScale(QwtPlot::yRight,
    8. range().minValue(), range().maxValue() );
    9. plot->enableAxis(QwtPlot::yRight);
    10. plot->replot();
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    The spectrogram example shows a colorbar in the range [0, 10].

    Uwe

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