直接上代码：

1 QImage Image;
2     Image.load("d:/test.jpg");
3     QPixmap pixmap = QPixmap::fromImage(Image);
4     int with = ui->labPic->width();
5     int height = ui->labPic->height();
6     QPixmap fitpixmap = pixmap.scaled(with, height, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);  // 饱满填充
7     //QPixmap fitpixmap = pixmap.scaled(with, height, Qt::KeepAspectRatio, Qt::SmoothTransformation);  // 按比例缩放
8     ui->labPic->setPixmap(fitpixmap);