Painting on a QGraphicsScene without loosing the picture already on it. Qt C++ -


so question says, have qgraphicsview on ui. have made function puts image onto qgraphicsview:

// read new image file qimage image(":/images/myfile.png");  /// declare pointer scene qgraphicsscene *scene = new qgraphicsscene();  // add pixmap scene qimage 'image' scene->addpixmap(qpixmap::fromimage(image));  // set scene equal height , width of map image scene->setscenerect(0,0,image.width(),image.height());  // set scene graphicsview on ui ui->graphicsview->setscene(scene);

however want able paint dots @ specific x y values on image. have function quite nicely function called dots appear , picture vanishes :(. know because im setting scene again 1 dots on program gets rid of 1 thats using (the image one)

    for(unsigned int = 0; < pixels.size(); i++)     {         x = pix_iter->second;         y = pix_iter->first;          scene->addellipse(x, y, 1, 1, pen, qbrush(qt::solidpattern));          pix_iter++;     }     ui->graphicsview->setscene(scene);

anyway dont know update scene add dots instead of setting new one

any appreciated.

in second snippet, re-create scene? why don't use ui->graphicsview->scene() , add dots it?


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