c++ - Cropping an image on Qt -

i'm building simple image editor on qt.i have opened image on qgraphicsview , want able crop it.after lot of search came code doesn't work.

void mainwindow::on_openbutton_pressed() {     qstring imagepath=qfiledialog::getopenfilename(this,tr("open file"),"",tr("jpeg (*.jpg *.jpeg);;png (*.png)"));     imageobject=new qimage();     imageobject->load(imagepath);     image=qpixmap::fromimage(*imageobject);     scene = new qgraphicsscene(this);     scene->addpixmap(image);     scene->setscenerect(image.rect());     ui->graphicsview->setscene(scene);     ui->graphicsview->setdragmode(qgraphicsview::rubberbanddrag);     showevent(); }  void mainwindow::mousepressevent(qmouseevent *event){     start=event->pos(); }  void mainwindow::mousereleaseevent(qmouseevent *event) {     end=event->pos(); }  void mainwindow::on_cropbutton_clicked() {     start=ui->graphicsview->mapfromscene(start);     end=ui->graphicsview->mapfromscene(end);     qrect rect(start, end);     cropped.size()=rect.size();     cropped=image.copy(rect);     ui->graphicsview->scene()->addpixmap(cropped);     ui->graphicsview->scene()->setscenerect(cropped.rect());     showevent(); } 

can find mistake or propose better way it? thank lot.