How can i draw a QImage via QPixmap on my Widged

MaXgOeKy

Hello,

I want to fill a QImage via setPixel() with three different colors: green, red and blue. After this I want to convert the image into a pixmap: QPixmap :: from image (myImage) and draw the pixmap with my painter myPainter.drawPixmap (pixmap) on the widged.

Problem: The program runs without errors but nothing has been drawn....

Here is code:
@void MainWindow::paintEvent(QPaintEvent *)
{
//TmpAttr
int xSize = _world->getWorldSize().first;
int ySize = _world->getWorldSize().second;
QRect playingField(10, 10, xSize, ySize);

enum type
{
fish = 1,
shark = 2,
water = 3,
error = 255
};

QPainter myPainter(this);
myPainter.fillRect(playingField, Qt::blue);

QImage testImage(playingField.size(), QImage::Format_Indexed8);
QVector<QRgb> _colors(256);
_colors[fish] = Qt::green;
_colors[shark] = Qt::red;
_colors[water] = Qt::blue;
_colors[error] = Qt::yellow;
testImage.setColorTable(_colors);

//Zeichne Pixel
for(int x = 0; x < xSize; x++)
{
    for (int y = 0; y < ySize; y++)
    {
        //std::cout << "Offset: " << counter << " Type: " << _world->getIndividumType(x, y) << std::endl;
        counter ++;
        
        switch (_world->getIndividumType(x, y))
        {
            case 1: //fish
                testImage.setPixel(x, y, fish);
                fishCounter++;
                break;
            case 2: //shark
                testImage.setPixel(x, y, shark);
                sharkCouner++;
                break;
            case 3: //water
                testImage.setPixel(x, y, water);
                waterCounter++;
                break;
            default: //error
                testImage.setPixel(x, y, error);
                std::cout << "Error at: " << x << " " << y << std::endl;
                break;
        }//end switch
    }//end for y
}//end for x

myPainter.drawPixmap(playingField, QPixmap::fromImage(testImage));

}//end paint@

Can anyone help me?

SGaist

Hi and welcome to devnet,

Not a direct answer to your question but it seems that you are complicating things, why not use a QLabel and set your pixmap on it ? You could update your counters using timerEvent and call update.

As for your question, what kind of widget is your MainWindow ?

MaXgOeKy

Whats the different between setting a pixmap on a Label and setting it on the widget itself? Did u have a excample for the the timerEvent?

How can i see what kind of widget i have?

Sorry but im realy new to qt :)

MaXgOeKy

No idea anyone, why nothing is drawn?

SGaist

The QLabel handles the painting part for you :)

@class MainWindow : public QWidget <- or QMainWindow etc...@

You can see how to use it in "QObject::startTimer":http://qt-project.org/doc/qt-4.8/qobject.html#startTimer

Also, I just checked the "QImage's documentation":http://qt-project.org/doc/qt-4.8/qimage.html#Format-enum drawing on a Format_Indexed8 image is not supported

andre

A few remarks:
I would recommend against doing the actual work generating the QImage in the paintEvent itself. The paintEvent needs to be fast, and your routine is making it slow. I would generate the image in another method and call update() on the widget when a repaint is needed based on the new image.

You can also directly render a QImage. It depends on your platform if converting to QPixmap first (once, instead of in every call to paintEvent!) has speed benefits.