Draw QPixmap in DrawBackground method from QGraphicsView

hobbyProgrammer

I would like to draw a QPixmap in the drawBackground method of a QGraphicsView class.

this is my GraphicsView.cpp

#include "graphicsview.h"

GraphicsView::GraphicsView(QWidget *parent)
    : QGraphicsView(parent)
{
    scene = new QGraphicsScene(this);
    setScene(scene);

}

void GraphicsView::scaleView(qreal scaleFactor)
{
    qreal factor = transform().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width();
    if (factor < 0.07 || factor > 100)
        return;

    scale(scaleFactor, scaleFactor);
}

void GraphicsView::drawBackground(QPainter *painter, const QRectF &rect)
{
    Q_UNUSED(rect);

    QRectF sceneRect = this->sceneRect();
    painter->drawPixmap(sceneRect, pixmap, pixmap.rect());
}

void GraphicsView::zoomIn()
{
    scaleView(qreal(1.2));
}

void GraphicsView::zoomOut()
{
    scaleView(1 / qreal(1.2));
}

void GraphicsView::open()
{
    QString filename = QFileDialog::getOpenFileName(this,tr("Open File"), QDir::currentPath(), tr("Image Files(*.png *.jpg *.jpeg)"));
    pixmap = QPixmap(filename);
    update();
}

Pl45m4

@hobbyProgrammer

You want to set an image (instead of just white) as background for your GraphicsView?

setBackgroundBrush(QImage("PATH"));

Where does your PixMap come from? External image file or painted inside your GraphicsScene as well?

https://doc.qt.io/qt-5/qgraphicsview.html#drawBackground

hobbyProgrammer

@Pl45m4 okay, but then this should work, right?
I'm still getting a white background...

#include "graphicsview.h"

GraphicsView::GraphicsView(QWidget *parent) : QGraphicsView(parent)
{
    scene = new QGraphicsScene();
    this->setScene(scene);
    this->setAlignment(Qt::AlignLeft | Qt::AlignTop);
    LoadImage();
}

void GraphicsView::LoadImage()
{
    filename = QFileDialog::getOpenFileName(this, tr("Open Image"), QDir::currentPath(), tr("Image Files (*.png *.jpg *.jpeg)"));
    this->update();
}

void GraphicsView::drawBackground(QPainter *painter, const QRectF &rect)
{
    Q_UNUSED(rect)
    painter->setBackground(QImage(filename));
}

jsulm

@hobbyProgrammer It looks like you do not check whether the image was actually loaded successfully.

hobbyProgrammer

@jsulm @Pl45m4 okay, but it keeps repeating the image and I would like there to be just 1 image, that can be zoomed in and out. Do you know how to do that?