How can I scale QGraphicsItems?

Ceng0

Hi , how can i scale my QGraphicsItem? I have multiple items. And i would like to scale these QGraphicsItems, something like zoom.. QGraphicsView::fitInView not working. How can i do?
widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QGraphicsPixmapItem>
#include <QGraphicsScene>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
    QGraphicsPixmapItem *pixmapItem;
    QGraphicsScene *scene;
    void addToScene(QGraphicsItem*);

private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    scene = new QGraphicsScene;
    pixmapItem = new QGraphicsPixmapItem(QPixmap(/*directory*/)); 
   // more graphicsitems will be added
    ui->graphicsView->setScene(scene);
    addToScene(pixmapItem);

}

Widget::~Widget()
{
    delete ui;
}

void Widget::addToScene(QGraphicsItem *item){
    scene->addItem(item);
    item->setPos(0,0);
}

Current Positions - graphicsView is fixed. Paint skills :(

The situation I want

JonB

@Ceng0
A QGraphsItem can be scaled via https://doc.qt.io/qt-5/qgraphicsitem.html#setScale

Or your QPixmaps can be scaled via https://doc.qt.io/qt-5/qpixmap.html#scaled

QGraphicsView::fitInView() does one particular scaling across all graphics items. The whole view's scale can be set via https://doc.qt.io/qt-5/qgraphicsview.html#scale.

Ketan__Patel__0011

Just Simply use fitInView Function like this

    scene->addItem(YOUR_ITEM);
    ui->graphicsView->fitInView(scene->sceneRect(), Qt::IgnoreAspectRatio);
    ui->graphicsView->setScene(scene);
    ui->graphicsView->setRenderHints(QPainter::SmoothPixmapTransform);
    ui->graphicsView->viewport()->update();
    ui->graphicsView->update();
    ui->graphicsView->show();

JonB

@Ketan__Patel__0011
@Ceng0 wrote:

QGraphicsView::fitInView not working

I took that to mean that he did not like the result he got for that, and wanted more control over individual item scaling/zooming.

But maybe you're right and he just meant that he could not get it to work?

I use fitInView(), it suits me. But in your code could you tell me:

Why do you need to do ui->graphicsView->viewport()->update()? I do not do that.
What does setRenderHints(QPainter::SmoothPixmapTransform) achieve? I have a map pixmap filling the whole scene, not individual shape/pixmap objects, what is your render hint used for, does it not affect me if all I do is zoom a background full-scene pixmap?

Ketan__Patel__0011

@JonB

He Can use QWheelEvent For Zooming And Scaling

@JonB said in How can I scale QGraphicsItems?:

Why do you need to do ui->graphicsView->viewport()->update()? I do not do that.

I am using QGraphicsView in My Threading Function And i am display QPixmaps continuously And Displaying
That's Why I Have to update My QGraphicsView viewport And For Avoid Flickering i am use setRenderhints For Smooth Pixmap Transformation

JonB

@Ketan__Patel__0011
OK, thank you for answering. I don't understand why that requires viewport()->update(). For my case I do not see any flickering, so maybe I don't need the SmoothPixmapTransform.

Ketan__Patel__0011

@JonB

So Whenever you will face any problem like this then try this way

Thank You