Clip existing ContourLines of QwtPlotSpectrogram

[Keir]

Greetings,
how do I crop/clip/erase those contours, that are outside of data?

[Uwe]

The contour lines are calculated from your data - so they can't be outside.

Are spectrogram and contour lines displayed from the same data object and the same plot item ?
Is your image a screenshot or something you generated with QwtPlot::print.
How did you limit the area of your spectrogram ?

Uwe

[Keir]

setBoundingRect(QwtDoubleRect(xmin,ymin,xmax-xmin,ymax-ymin));

setBoundingRect(QwtDoubleRect(xmin,ymin,xmax-xmin,ymax-ymin));

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within SpectrogramData:QwtRasterData. The spectrogram itself is bounded correctly.
regarding the raster data and contour data -

S = new QwtPlotSpectrogram;
    SpectrogramData D(fopen("in.txt","r"));
    S->setData(D);
    S->attach(Plot);
 QwtValueList contourLevels;
...calculating contourlevels...
 S->setContourLevels(contourLevels);
S->setDisplayMode(QwtPlotSpectrogram::ContourMode, true);
    Plot->replot();

S = new QwtPlotSpectrogram;
    SpectrogramData D(fopen("in.txt","r"));
    S->setData(D);
    S->attach(Plot);
 QwtValueList contourLevels;
...calculating contourlevels...
 S->setContourLevels(contourLevels);
S->setDisplayMode(QwtPlotSpectrogram::ContourMode, true);
    Plot->replot();

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Screenshot is taken by pressing PRINT SCREEN, cropping with mspaint and posting as jpeg.

[Uwe]

This is a bug in Qwt, but you can work around it easily:

virtual ContourLines YourRasterData::contourLines(
        const QwtDoubleRect &rect,
        const QSize &raster, const QList<double> &levels,
        int flags) const
{
    QwtDoubleRect area = rect;
    if ( boundingRect().isValid() )
        area &= boundingRect();
 
    return QwtRasterData::contourLines(area, raster, levels flags);
}

virtual ContourLines YourRasterData::contourLines(
        const QwtDoubleRect &rect,
        const QSize &raster, const QList<double> &levels,
        int flags) const
{
    QwtDoubleRect area = rect;
    if ( boundingRect().isValid() )
        area &= boundingRect();

    return QwtRasterData::contourLines(area, raster, levels flags);
}

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Or you can use the code from SVN ( 5.2 branch ).

Uwe

[Keir]

Superb! Thank you.

[jwieland]

Hi,

I am also trying to use contour in my program and confused about the qwt contour program. Do I need to implement some contour algorithm to fill my data with points of (x, y, v) or those points have been figured out by the qwt library? I mean, I have a set of (x, y, v) points but the number of those points is just a few and cannot certainly fill up all the display. And if I am to enter the data, where in the Qwt structure should I enter them?

Any help is greatly appreciated.