Can I draw in QGraphicsView on Qpixmap?

[Mikeeeeee]

Hi!
I created a drawing class in QGraphicsView .
But can I draw in QGraphicsView on Qpixmap?

[SGaist]

Hi,

Can you give more details about what you have implemented until now ?

[Mikeeeeee]

I implemented drawing on QGraphicsScene.
.h

#ifndef PAINTSCENE_H
#define PAINTSCENE_H

#include <QGraphicsScene>
#include <QGraphicsSceneMouseEvent>
#include "QGraphicsView"
#include <QTimer>
#include <QDebug>
//#include "QLabel"

class paintScene : public QGraphicsScene
{

    Q_OBJECT

public:
    explicit paintScene(QObject *parent = 0);
    ~paintScene();
    //QGraphicsView *myQGraphicsScene;
    //paintScene *scene; 


private:
    QPointF     previousPoint;    
    bool buttonIsPressed;

private:
    void mousePressEvent(QGraphicsSceneMouseEvent * event);
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
};

#endif // PAINTSCENE_H

.cpp

#include "paintscene.h"


paintScene::paintScene(QObject *parent) : QGraphicsScene(parent)
{
    //myQGraphicsScene = new QGraphicsView();
    //scene = new paintScene();       // Инициализируем графическую сцену
}

paintScene::~paintScene()
{

}

void paintScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    addEllipse(event->scenePos().x() - 5,
               event->scenePos().y() - 5,
               10,
               10,
               QPen(Qt::NoPen),
               QBrush(Qt::red));
    previousPoint = event->scenePos();
    buttonIsPressed = true;
}

void paintScene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
    if (buttonIsPressed)
    {
        addLine(previousPoint.x(),
                previousPoint.y(),
                event->scenePos().x(),
                event->scenePos().y(),
                QPen(Qt::red,10,Qt::SolidLine,Qt::RoundCap));
        previousPoint = event->scenePos();
    }
}

void paintScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
    buttonIsPressed = false;
}

I set 2 images for the scene. I would like to draw on the top Image,

#include "paint.h"
#include "ui_paint.h"
#include <QtWidgets>

Paint::Paint(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Paint)
{
    ui->setupUi(this);

    QImage mapImage("C:\\Users\\New Owner\\Downloads\\mapMain.png");
  


   /QImage base("C:\\Users\\New Owner\\Downloads\\mapMain.png"); // set to some file/size
    //верхняя картинка
   /QImage overlay("C:\\Users\\New Owner\\Downloads\\mapTop.png");  // set to some file/size


    scene = new paintScene();       // Инициализируем графическую сцену


    scene->addPixmap(QPixmap::fromImage(mapImage));//add image
    scene->addPixmap(QPixmap::fromImage(overlay));//add image


    newGraphicsView =  new graphicsView();
    newGraphicsView->setScene(scene);
    ui->verticalLayout->addWidget(newGraphicsView);

    timer = new QTimer();     
    connect(timer, &QTimer::timeout, this, &Paint::slotTimer);
    timer->start(100);    
}

[Mikeeeeee]

And I need to draw so that the old points are erased when drawing new ones

[SGaist]

Draw on the top image or add items on top of it ?

[Mikeeeeee]

But it does not need to erase the lower pixels

[SGaist]

Then why not delete associated items and create new ones after that ?

[Mikeeeeee]

I draw so:
h

#ifndef PAINTSCENE_H
#define PAINTSCENE_H

#include <QGraphicsScene>
#include <QGraphicsSceneMouseEvent>
#include "QGraphicsView"
#include <QTimer>
#include <QDebug>




class paintScene : public QGraphicsScene
{

    Q_OBJECT

public:
    explicit paintScene(QObject *parent = 0);
    ~paintScene();
    QPen myPen;
    QString paintOrDelete = "paint"; 




private:
    QPointF     previousPoint;     
    bool buttonIsPressed;

private:
    void mousePressEvent(QGraphicsSceneMouseEvent * event);
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);

};

#endif // PAINTSCENE_H

cpp

void paintScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    if (paintOrDelete == "paint")
    {
        addEllipse(event->scenePos().x() -  myPen.width()/2,
                   event->scenePos().y() -  myPen.width()/2,
                   myPen.width(),
                   myPen.width(),
                   QPen(Qt::NoPen),
                   QBrush(myPen.color()));
        previousPoint = event->scenePos();
        buttonIsPressed = true;

    }   
}

I here to build a class for move and delete:
h

#ifndef MOVEITEM_H
#define MOVEITEM_H

#include <QObject>
#include <QGraphicsItem>
#include <QPainter>
#include <QGraphicsSceneMouseEvent>
#include <QDebug>
#include <QCursor>
 #include <QApplication>

class MoveItem : public QObject, public QGraphicsItem
{
    Q_OBJECT
public:
    explicit MoveItem(QObject *parent = 0);
    ~MoveItem();

signals:

private:
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);

public slots:
};

#endif // MOVEITEM_H

cpp

#include "moveitem.h"

MoveItem::MoveItem(QObject *parent) :
    QObject(parent), QGraphicsItem()
{

}

MoveItem::~MoveItem()
{

}

QRectF MoveItem::boundingRect() const
{
    return QRectF (-30,-30,60,60);
}

void MoveItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->setPen(Qt::black);
    painter->setBrush(Qt::green);
    painter->drawRect(-30,-30,60,60);
    Q_UNUSED(option);
    Q_UNUSED(widget);
}

void MoveItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
    this->setPos(mapToScene(event->pos()));
}

void MoveItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    this->setCursor(QCursor(Qt::ClosedHandCursor));
    Q_UNUSED(event);

    if (QApplication::mouseButtons() == Qt::RightButton)
    {
        qDebug()<<"delete";
        this->deleteLater();
    }
}

void MoveItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
    this->setCursor(QCursor(Qt::ArrowCursor));
    Q_UNUSED(event);
}

If I add this class to the project, it does not work.