howto; create an image, fill pixels with color, display on scene

[robsofmar]

Hi there,

I would like to create a image (on the fly), fill it with colors and then display it using a QGraphicsScene. I managed to write the code but the pixels that I made blue are not visible. Any ideas on what is wrong?

* part of the view class (the main code regarding the question is in the initializeScene function):

cGeometryViewer::cGeometryViewer(QWidget *parent) :
    QGraphicsView(parent)
{
    m_scene = new QGraphicsScene(0, 0, MATRIXWIDTH, MATRIXHEIGHT);
    setScene(m_scene);
}
 
void cGeometryViewer::setGeometry(cGeometry *geometry)
{
    m_geometry = geometry;
    initializeScene();
}
 
void cGeometryViewer::initializeScene()
{
    QImage img(MATRIXWIDTH, MATRIXHEIGHT,QImage::Format_ARGB32);
 
    //just to find out if it works fill a rectangle with black pixels
    for(int x=0; x<100; x++)
        for(int y=0; y<100; y++)
            img.setPixel(QPoint(x,y), Qt::black);
 
    QGraphicsPixmapItem pmi(QPixmap::fromImage(img));
    m_scene->addItem(&pmi);
    show();
}

cGeometryViewer::cGeometryViewer(QWidget *parent) :
    QGraphicsView(parent)
{
    m_scene = new QGraphicsScene(0, 0, MATRIXWIDTH, MATRIXHEIGHT);
    setScene(m_scene);
}

void cGeometryViewer::setGeometry(cGeometry *geometry)
{
    m_geometry = geometry;
    initializeScene();
}

void cGeometryViewer::initializeScene()
{
    QImage img(MATRIXWIDTH, MATRIXHEIGHT,QImage::Format_ARGB32);

    //just to find out if it works fill a rectangle with black pixels
    for(int x=0; x<100; x++)
        for(int y=0; y<100; y++)
            img.setPixel(QPoint(x,y), Qt::black);

    QGraphicsPixmapItem pmi(QPixmap::fromImage(img));
    m_scene->addItem(&pmi);
    show();
}

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* and part of the main code;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    m_geometry = new cGeometry();
    m_viewer = new cGeometryViewer(ui->frameMain);
    m_viewer->setGeometry(m_geometry);
}

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

    m_geometry = new cGeometry();
    m_viewer = new cGeometryViewer(ui->frameMain);
    m_viewer->setGeometry(m_geometry);
}

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Thanks in advance!
Rob

[spirit]

You should create all QGraphicsPixmapItem on the heap, because they are going to be destroyed after outing of the function scope.