How to remove cropped rect from QImage/QLabel?

Question

I did sub-classing to include mouse click function. Here, a rectangle can be chosen by mousePressEvent , mouseMoveEvent and mouseReleaseEvent . When I am trying to chose another rectangle, my previous rectangle is not being removed. It is still displaying with my previous drawn rectangle, which I don't want to display. I want to chose and display only one rectangle. I meant when I press again to chose another rectange, the previous one should be removed.

I included here my subclass named mouse_crop

mouse_crop .h is as follows

#ifndef MOUSE_CROP_H
#define MOUSE_CROP_H

#include <QMainWindow>
#include <QObject>
#include <QWidget>
#include <QMouseEvent>
#include <QLabel>
#include <QRubberBand>

class mouse_crop : public QLabel
{
    Q_OBJECT

public:

mouse_crop(QWidget *parent=0);
QRubberBand *rubberBand;
QPoint origin, ending;

protected:
    void mousePressEvent(QMouseEvent *ev);
    void mouseMoveEvent(QMouseEvent *ev);
    void mouseReleaseEvent(QMouseEvent *ev);

signals:
    void sendMousePosition(QPoint&);
    void sendMouseEnding(QPoint&);
};

#endif // MOUSE_CROP_H`

And mouse_crop.cpp is as follows

#include "mouse_crop.h"

mouse_crop::mouse_crop(QWidget *parent):QLabel (parent)
{

}

void mouse_crop::mousePressEvent(QMouseEvent *ev)
{
    origin = ev->pos();
    rubberBand = new QRubberBand(QRubberBand::Rectangle, this);
    if(ev->button()== Qt::LeftButton || ev->button()== Qt::RightButton)
    {
        rubberBand->show();
        emit sendMousePosition(origin);
    }
}

void mouse_crop::mouseMoveEvent(QMouseEvent *ev)
{
    rubberBand->setGeometry(QRect(origin, ev->pos()).normalized());
}

void mouse_crop::mouseReleaseEvent(QMouseEvent *ev)
{
    ending = ev->globalPos();
    if(ev->button()== Qt::LeftButton || ev->button()== Qt::RightButton)
    {
        emit sendMouseEnding(ending);
    }
}

Can any one tell me how to solve this? Thanks in advance.

Answer 1

The problem is caused because every time you press the mouse you are creating a new QRubberBand, what you must do is create only a QRubberBand, hide it and show it when necessary.

mouse_crop::mouse_crop(QWidget *parent)
    : QLabel(parent)
{
    rubberBand = new QRubberBand(QRubberBand::Rectangle, this);
    rubberBand->hide();
}

void mouse_crop::mousePressEvent(QMouseEvent *ev)
{
    origin = ev->pos();
    rubberBand->setGeometry(QRect(origin, origin));

    if(ev->button()== Qt::LeftButton || ev->button()== Qt::RightButton)
    {
        rubberBand->show();
        emit sendMousePosition(origin);
    }
}

void mouse_crop::mouseMoveEvent(QMouseEvent *ev)
{
    rubberBand->setGeometry(QRect(origin, ev->pos()).normalized());
}

void mouse_crop::mouseReleaseEvent(QMouseEvent *ev)
{
    ending = ev->globalPos();
    if(ev->button()== Qt::LeftButton || ev->button()== Qt::RightButton)
    {
        emit sendMouseEnding(ending);
    }
}