How to use curve fitting

[nightroad]

Hi there,

I'm drawing strokes with mouse movement. I'm keeping all points in a QVector<QPointF> or directly QPointF*, How can i apply curve fitting algorithm in my custom widget its own paintEvent. I tried somethings but i couldn't do that. Thanks ...

#ifndef MYWIDGET_H
#define MYWIDGET_H
 
#include <QWidget>
#include <QtGui>
 
class MyWidget : public QWidget
{
    Q_OBJECT
public:
    explicit MyWidget(QWidget *parent = 0);
    virtual ~MyWidget();
 
    void paintEvent(QPaintEvent *event);
 
    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);
 
private:
    QPointF m_start;
    QPointF m_end;
    QPolygonF m_points;
    QPolygonF m_fittedPoints;
 
    bool m_isFitting;
 
};
 
#endif // MYWIDGET_H

#ifndef MYWIDGET_H
#define MYWIDGET_H

#include <QWidget>
#include <QtGui>

class MyWidget : public QWidget
{
    Q_OBJECT
public:
    explicit MyWidget(QWidget *parent = 0);
    virtual ~MyWidget();

    void paintEvent(QPaintEvent *event);

    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);

private:
    QPointF m_start;
    QPointF m_end;
    QPolygonF m_points;
    QPolygonF m_fittedPoints;

    bool m_isFitting;

};

#endif // MYWIDGET_H

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#include "mywidget.h"
 
#include <qwt_spline.h>
#include <qwt_curve_fitter.h>
 
QPolygonF interpolate(const QPolygonF& points, int numValues)
{
    QwtSpline spline;
    QwtSplineCurveFitter curveFitter;
    bool pResult = true;
    Q_ASSERT(pResult != spline.setPoints(points));
    if ( !pResult ) {
	return points;
    }
 
//    curveFitter.setSpline(spline);
    QPolygonF fitted = curveFitter.fitCurve(points);
 
    return fitted;
}
 
MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{
}
 
MyWidget::~MyWidget()
{
}
 
void MyWidget::mousePressEvent(QMouseEvent *event)
{
    m_isFitting = false;
    m_start = event->pos();
    m_end = event->pos();
}
 
void MyWidget::mouseMoveEvent(QMouseEvent *event)
{
    m_start = m_end;
    m_end = event->pos();
 
//    m_points.append(m_start);
//    m_points.append(m_end);
    m_points << m_start << m_end;
    update();
}
 
void MyWidget::mouseReleaseEvent(QMouseEvent *event)
{
    // I want to apply curve fitting to m_points here
    m_fittedPoints = interpolate(m_points, m_points.size());
    // m_fittedPoints is equal to fitted points
    m_isFitting = true;
    update();
}
 
void MyWidget::paintEvent(QPaintEvent *event)
{
 
    QPainter painter(this);
    painter.setPen(Qt::SolidLine);
 
    if (!m_isFitting)
	painter.drawLines(m_points.data(), m_points.size()/2);
    else
	painter.drawLines(m_fittedPoints.data(), m_fittedPoints.size()/2);
}

#include "mywidget.h"

#include <qwt_spline.h>
#include <qwt_curve_fitter.h>

QPolygonF interpolate(const QPolygonF& points, int numValues)
{
    QwtSpline spline;
    QwtSplineCurveFitter curveFitter;
    bool pResult = true;
    Q_ASSERT(pResult != spline.setPoints(points));
    if ( !pResult ) {
	return points;
    }

//    curveFitter.setSpline(spline);
    QPolygonF fitted = curveFitter.fitCurve(points);

    return fitted;
}

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{
}

MyWidget::~MyWidget()
{
}

void MyWidget::mousePressEvent(QMouseEvent *event)
{
    m_isFitting = false;
    m_start = event->pos();
    m_end = event->pos();
}

void MyWidget::mouseMoveEvent(QMouseEvent *event)
{
    m_start = m_end;
    m_end = event->pos();

//    m_points.append(m_start);
//    m_points.append(m_end);
    m_points << m_start << m_end;
    update();
}

void MyWidget::mouseReleaseEvent(QMouseEvent *event)
{
    // I want to apply curve fitting to m_points here
    m_fittedPoints = interpolate(m_points, m_points.size());
    // m_fittedPoints is equal to fitted points
    m_isFitting = true;
    update();
}

void MyWidget::paintEvent(QPaintEvent *event)
{

    QPainter painter(this);
    painter.setPen(Qt::SolidLine);

    if (!m_isFitting)
	painter.drawLines(m_points.data(), m_points.size()/2);
    else
	painter.drawLines(m_fittedPoints.data(), m_fittedPoints.size()/2);
}

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