Results 1 to 3 of 3

Thread: How to pick the line of a curve? (Pt BR Como pegar a linha de uma curva?)

  1. #1
    Join Date
    Jul 2013
    Posts
    6
    Qt products
    Qt5
    Platforms
    Windows

    Default How to pick the line of a curve? (Pt BR Como pegar a linha de uma curva?)

    I have a simple curve with only two point. I wonder if there is a way to identify the line? I need to identify when I click on the line, when a polygon touches the line and drag the line to anywhere in the graph.

    (Pt BR)Possuo uma curva simples com apenas dois ponto. Gostaria de saber se existe uma maneira de identificar a reta? Preciso identificar quando clico na reta, quando algum poligono encosta na reta e arrastar essa reta para qualquer lugar do gráfico.

  2. #2
    Join Date
    Jul 2013
    Posts
    6
    Qt products
    Qt5
    Platforms
    Windows

    Default Re: How to pick the line of a curve? (Pt BR Como pegar a linha de uma curva?)

    After some research and testing there is the answer to click on the line. Thank those who have thought about.

    const bool CLASSE::checkClickOnLine(const QPoint& _pos) const
    {
    const QwtPlot *plot = this->plot();
    if ( plot == NULL )
    return false;

    // translate pos into the plot coordinates
    const QPointF& curvePosF = transformWindowToCanvas(_pos);

    const QwtPlotItemList curves = plot->itemList( QwtPlotItem::Rtti_PlotCurve );
    for ( int i = curves.size() - 1; i >= 0; --i )
    {
    const QLineF line = curveLineAt( static_cast<const QwtPlotCurve *>( curves[i] ), curvePosF.x());
    if ( !line.isNull() )
    {
    /**
    * Similarity of triangle - Semelhança de triângulo : ((y2-y1)/(x2-x1)) = ((y3-y1)/(x3-x1))
    * P3 is a clicked point
    **/
    const double xP1 = plot->canvasMap(QwtPlot::xBottom).transform(line.p1().x ());
    const double yP1 = line.p1().y();
    const double xP2 = plot->canvasMap(QwtPlot::xBottom).transform(line.p2().x ());
    const double yP2 = line.p2().y();
    const double xP3 = plot->canvasMap(QwtPlot::xBottom).transform(curvePosF.x ());
    const double yP3 = curvePosF.y();

    if ((xP2 - xP1) == 0 || ( xP3 - xP1 ) == 0)
    return false;

    qreal T1 = (yP2 - yP1)/(xP2 - xP1);
    qreal T2 = ( yP3 - yP1 )/( xP3 - xP1 );

    if (T2 > 0 && T1 - TOLERANCE < T2 && T1 + TOLERANCE > T2 ) //TOLERANCE = 0.025
    return true;
    }
    }

    return false;
    }

    QLineF CLASSE:curveLineAt( const QwtPlotCurve *curve, double x ) const
    {
    QLineF line;

    if ( curve->dataSize() >= 2 )
    {
    const QRectF br = curve->boundingRect();
    if ( br.isValid() && x >= br.left() && x <= br.right() )
    {
    int index = qwtUpperSampleIndex<QPointF>(
    *curve->data(), x, compareX() );

    if ( index == -1 &&
    x == curve->sample( curve->dataSize() - 1 ).x() )
    {
    // the last sample is excluded from qwtUpperSampleIndex
    index = curve->dataSize() - 1;
    }
    if ( index > 0 )
    {
    line.setP1( curve->sample( index - 1 ) );
    line.setP2( curve->sample( index ) );
    }
    }
    }
    return line;
    }

    struct compareX
    {
    inline bool operator()( const double x, const QPointF &pos ) const
    {
    return ( x < pos.x() );
    }
    };
    Last edited by BrFla; 24th July 2013 at 16:03.

  3. #3
    Join Date
    Jul 2013
    Posts
    6
    Qt products
    Qt5
    Platforms
    Windows

    Default Re: How to pick the line of a curve? (Pt BR Como pegar a linha de uma curva?)

    Improved. Melhorado
    Use the comments from the previous example. Uso comentarios do exemplo anterior
    It can be used for one or more curves in the graph. Este método pode ser usado quando voce possuir em seu gráfico uma ou mais curvas.
    I return the clicked curve. Agora retorno a curva clicada.

    QwtPlotCurve* CLASS::clickedCurve( const QPoint& _pos ) const
    {
    const QwtPlot *plot = this->plot();
    if ( plot == NULL )
    return NULL;

    // translate pos into the plot coordinates
    const QPointF &curvePosF = transformWindowToCanvas(_pos);

    const QwtPlotItemList &curves = plot->itemList( QwtPlotItem::Rtti_PlotCurve );
    for ( int i = curves.size() - 1; i >= 0; --i )
    {

    const QLineF line = curveLineAt( static_cast<const QwtPlotCurve *>( curves[i] ), curvePosF.x()); //Returns the two points that created the line
    if ( !line.isNull() )
    {
    const double xP1 = plot->canvasMap(QwtPlot::xBottom).transform(line.p1().x ());
    const double yP1 = line.p1().y();
    const double xP2 = plot->canvasMap(QwtPlot::xBottom).transform(line.p2().x ());
    const double yP2 = line.p2().y();
    const double xP3 = plot->canvasMap(QwtPlot::xBottom).transform(curvePosF.x ());
    const double yP3 = curvePosF.y();

    if ((xP2 - xP1) == 0 || ( xP3 - xP1 ) == 0)
    return NULL;

    qreal RazaoT1 = (yP2 - yP1)/(xP2 - xP1);
    qreal RazaoT2 = ( yP3 - yP1 )/( xP3 - xP1 );

    if (RazaoT2 > 0 && RazaoT1 - TOLERANCIA < RazaoT2 && RazaoT1 + TOLERANCIA > RazaoT2)
    return static_cast<QwtPlotCurve *>( curves[i] );

    }
    }

    return NULL;
    }

    const QPointF CLASS::transformWindowToCanvas( const QPoint& _pos ) const
    {
    const QwtPlot* pPlot = this->plot();

    const double dX = pPlot->canvasMap( QwtPlot::xBottom ).invTransform( _pos.x() );
    const double dY = pPlot->canvasMap( QwtPlot::yLeft ).invTransform( _pos.y() );

    return QPointF(dX, dY);
    }

    I hope I have helped
    Last edited by BrFla; 26th July 2013 at 14:36.

Similar Threads

  1. Pick size of QPixmap / icon based on DPI / user prefs
    By stephelton in forum Qt Programming
    Replies: 1
    Last Post: 12th January 2013, 07:54
  2. Problem with pick a QGraphicsItem
    By lni in forum Qt Programming
    Replies: 1
    Last Post: 13th December 2012, 17:05
  3. Replies: 4
    Last Post: 29th April 2010, 06:11
  4. Replies: 2
    Last Post: 24th April 2009, 17:22
  5. Replies: 4
    Last Post: 11th September 2006, 14:13

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Digia, Qt and their respective logos are trademarks of Digia Plc in Finland and/or other countries worldwide.