painting from -0.5 value

I try to paint a spectrogram from QVector data.
I expect that will draw from x-zero... but result on the screenshot:

Attachment 8495

here is my code:

Code:

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// plot.h
 
#include <qwt_plot.h>
#include <qwt_plot_spectrogram.h>
 
class QwtPlotZoomer;
class SpectrogramData;
class SpectrogramDataFile;
 
class Plot: public QwtPlot {
    Q_OBJECT
 
public:
    Plot( QWidget * = NULL );
 
public Q_SLOTS:
    void showSpectrogram( bool on );
 
    void addColumn(const QVector<int> &col);
 
 
private:
    QwtPlotSpectrogram *d_spectrogram;
    SpectrogramData *sData;
    SpectrogramDataFile *sDataFile;
    QwtPlotZoomer* zoomer;
};

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Code:

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// plot.cpp
 
#include <QFile>
#include <QDebug>
#include <qwt_raster_data.h>
#include <qprinter.h>
#include <qprintdialog.h>
#include <qwt_color_map.h>
#include <qwt_plot_spectrogram.h>
#include <qwt_scale_widget.h>
#include <qwt_scale_draw.h>
#include <qwt_plot_zoomer.h>
#include <qwt_plot_panner.h>
#include <qwt_plot_layout.h>
#include <qwt_plot_renderer.h>
#include "plot.h"
#include "SpectrogramData.h"
#include "CONST.h"
 
const qreal minX = -1.0; // if it will 0.0 we have the same result, just cut axis
 
//------------------------------------------------------------------------------------------
class MyZoomer: public QwtPlotZoomer {
public:
    MyZoomer( QwtPlotCanvas *canvas ):
        QwtPlotZoomer( canvas ) {
        setTrackerMode( AlwaysOn );
    }
 
    virtual QwtText trackerTextF( const QPointF &pos ) const {
        QColor bg( Qt::white );
        bg.setAlpha( 200 );
 
        QwtText text = QwtPlotZoomer::trackerTextF( pos );
        text.setBackgroundBrush( QBrush( bg ) );
        return text;
    }
};
 
//------------------------------------------------------------------------------------------
class SpectrogramData: public QwtRasterData {
 
private:
    int maxX;
    int maxY;
 
    vecArray column;
    Matrix detectionMatrix;
 
public:
    SpectrogramData() {
        maxX = 0;
        maxY = 359;
 
        setInterval(Qt::XAxis, QwtInterval(minX, maxX));
        setInterval(Qt::YAxis, QwtInterval(minX, maxY));
        setInterval(Qt::ZAxis, QwtInterval(minX, 10.0));
    }
 
    void setMaxXIncremet() {
        ++maxX;
        setInterval(Qt::XAxis, QwtInterval(minX, maxX));
    }
 
    void setMaxX(const int val) {
        setInterval(Qt::XAxis, QwtInterval(minX, val));
    }
 
    void setMaxY(const int val) {
        setInterval(Qt::YAxis, QwtInterval(0.0, val));
    }
 
    void addColumn(const QVector<int> &col) {
        detectionMatrix.push_back(col);
    }
 
    virtual double value(double x, double y) const {
        int ix = qRound(x);
        int iy = qRound(y);
 
        if ( (ix >= 0) && (ix < maxX) && (iy >= 0) && (iy < maxY) ) {
//            qDebug() << x;
            return detectionMatrix[ix][iy];
        }
        return 0;
    }
};
 
//------------------------------------------------------------------------------------------
class ColorMap: public QwtLinearColorMap {
public:
    ColorMap():
        QwtLinearColorMap( Qt::darkCyan, Qt::red ) {
        addColorStop( 0.6, Qt::cyan );
        //        addColorStop( 0.6, Qt::green );
        addColorStop( 0.9, Qt::yellow );
    }
};
 
//------------------------------------------------------------------------------------------
Plot::Plot( QWidget *parent ):
    QwtPlot( parent ) {
 
    sData = new SpectrogramData();
    sDataFile = new SpectrogramDataFile();
    d_spectrogram = new QwtPlotSpectrogram();
    d_spectrogram->setRenderThreadCount( 0 ); // use system specific thread count
 
    d_spectrogram->setColorMap(new ColorMap());
 
    d_spectrogram->setData( sData );
    d_spectrogram->attach( this );
 
    const QwtInterval zInterval = d_spectrogram->data()->interval( Qt::ZAxis );
        QwtScaleWidget *rightAxis = axisWidget(QwtPlot::yRight); // A color bar on the right axis
    rightAxis->setTitle(tr("Amplitude"));
    rightAxis->setColorBarEnabled(true);
    rightAxis->setColorMap(zInterval, new ColorMap());
 
    setAxisScale( QwtPlot::yRight, zInterval.minValue(), zInterval.maxValue() );
    enableAxis( QwtPlot::yRight );
 
    plotLayout()->setAlignCanvasToScales(true);
    replot();
 
    zoomer = new MyZoomer(canvas());
    zoomer->setMousePattern( QwtEventPattern::MouseSelect2,
                             Qt::RightButton, Qt::ControlModifier );
    zoomer->setMousePattern( QwtEventPattern::MouseSelect3,
                             /*Qt::Key_Delete*/Qt::RightButton );
 
        QwtPlotPanner *panner = new QwtPlotPanner(canvas());
        panner->setAxisEnabled(QwtPlot::yRight, false);
        panner->setMouseButton(Qt::MidButton);
        panner->setMouseTracking(true);
 
 
    const QFontMetrics fm( axisWidget( QwtPlot::yLeft )->font() );
    QwtScaleDraw *sd = axisScaleDraw( QwtPlot::yLeft );
    sd->setMinimumExtent( fm.width( "100.00" ) );
 
    const QColor c(Qt::darkBlue);
    zoomer->setRubberBandPen(c);
    zoomer->setTrackerPen(c);
}
 
 
//------------------------------------------------------------------------------------------
void Plot::addColumn(const QVector<int> &col) {
    sData->addColumn(col);
    sData->setMaxXIncremet();
    const QwtInterval xInterval = d_spectrogram->data()->interval(Qt::XAxis);
    const QwtInterval yInterval = d_spectrogram->data()->interval(Qt::YAxis);
 
    QRect rectTmp(QPoint(0, 0), QSize(xInterval.maxValue(), yInterval.maxValue()));
    zoomer->setZoomBase(rectTmp);
    replot();
}
 
//------------------------------------------------------------------------------------------
void Plot::showSpectrogram( bool on ) {
    d_spectrogram->setDisplayMode( QwtPlotSpectrogram::ImageMode, on );
    d_spectrogram->setDefaultContourPen( on ? QPen() : QPen( Qt::NoPen ) );
    replot();
}

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fill vector:

Code:

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QVector<int> col;
 
    for(int i = 0; i != 360; i++) {
        addColumn.push_back(randInt(1, 10));
    }

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so why is it painting from -0.5 would you explain?

Quote:

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Originally Posted by layer

so why is it painting from -0.5 would you explain?

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Your raster data object claims to have values for any position ( = you didn't set valid intervals with QwtRasterData::setInterval() for X/Y axes ).
The reason why you get a different color starting at > -0.5 is because your SpectrogramData::value() implementation rounds to 0 returning a value from your matrix - instead of the default 0.

As your code doesn't do much beside returning values from a value matrix I recommend to use QwtMatrixRasterData. Check the rasterview example.

Uwe

Quote:

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Originally Posted by Uwe

Your raster data object claims to have values for any position ( = you didn't set valid intervals with QwtRasterData::setInterval() for X/Y axes ).
The reason why you get a different color starting at > -0.5 is because your SpectrogramData::value() implementation rounds to 0 returning a value from your matrix - instead of the default 0.

As your code doesn't do much beside returning values from a value matrix I recommend to use QwtMatrixRasterData. Check the rasterview example.

Uwe

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a checked rasterview example, it's easier to use in my case, you're certainly right.
also I read many threads about Qwt, thank you Uwe for wonderful Lib.

but smth in this situation (with this example) I didn't understand exactly but I want:)

so as you can see in the code I use setInterval() for X, it's not enough?

step by step:

Code:

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addColumn(col); // push QVector<int> in QVector<QVector<int>>

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then

Code:

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//setMaxXIncremet();
++maxX;
setInterval(Qt::XAxis, QwtInterval(0.0, maxX)); // here I try to change Interval on X

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and then

Code:

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replot();

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You said that

Quote:

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is because your SpectrogramData::value() implementation rounds to 0 returning a value from your matrix - instead of the default 0.

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am I right it's about this code?

Code:

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int ix = qRound(x);
int iy = qRound(y);

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Uwe, can't make out what I have to change to get the result I need (painting from 0)?

Don't know about the code snippets from your second posting, but in the original code minX is set to -1.0 used in setInterval( XAxis, minX, ...). So here you indicate that you have valid values starting at -1,0.

You didn't implement pixelHint() what indicates, that you can return useful values for any resolution ( of course you could implement a valid pixelHint(), what might increase performance significantly depending on the ratio between screen resolution and hint ).

In your value() method you are rounding to the next integer, so f.e -0.499 is rounded to 0.. That's why you see the values from your first column displayed in the range ]-0.5, 0.5] on the X-axis.

But again: use QwtMatrixRasterData. instead of reinventing the wheel.

Uwe

Quote:

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Originally Posted by Uwe

use QwtMatrixRasterData. instead of reinventing the wheel.
Uwe

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I agree, thanks a lot again