Qt打开，保存，另存为图片

QString filename=QFileDialog::getOpenFileName(this,tr("选择图像"),"",tr("Images (*.png *.bmp *.jpg)"));
if(filename.isEmpty())
return;
else
{
QImage img;
if(!(img.load(filename))) //加载图像
{
QMessageBox::information(this, tr("打开图像失败"),tr("打开图像失败!"));
return;
}
ui->label->setPixmap(QPixmap::fromImage(img.scaled(ui->label->size())));
}

QString filename1 = QFileDialog::getSaveFileName(this,tr("Save Image"),"",tr("Images (*.png *.bmp *.jpg)")); //选择路径
QScreen *screen = QGuiApplication::primaryScreen();
screen->grabWindow(ui->label->winId()).save(filename1);

Mat img = imread("D:/1.jpg",1);
filename = QFileDialog::getSaveFileName(this,tr("Save Image"),"",tr("Images (*.png *.bmp *.jpg)")); //选择路径
string fileAsSave = filename.toStdString();
imwrite(fileAsSave,img);