在头文件mainwindow.h中先声明以下类：
1 #include <QImage>
2 #include <QPixmap>
3 #include <QFileDialog>
4 #include <QMessageBox>
5 #include <QScreen>
6 #include <QGuiApplication>
在私有对象下声明这几个变量，用于存放文件夹地址。
1 /* 保存路径*/
2 QString runPath;
3 QString hglpName;
4 QString hglpPath;
1 runPath = QCoreApplication::applicationDirPath(); //获取exe路径
2 hglpName = "photo";
3 hglpPath = QString("%1/%2").arg(runPath).arg(hglpName);
打开按钮槽函数实现：
1 void MainWindow::on_pushButton_clicked()
2 {
3 QString filename=QFileDialog::getOpenFileName(this,tr("选择图像"),"",tr("Images (*.png *.bmp *.jpg)"));
4 if(filename.isEmpty())
5 return;
6 else
7 {
8 QImage img;
9 if(!(img.load(filename))) //加载图像
10 {
11 QMessageBox::information(this, tr("打开图像失败"),tr("打开图像失败!"));
12 return;
13 }
14 ui->label->setPixmap(QPixmap::fromImage(img.scaled(ui->label->size())));
15 }
16 }
另存为按钮槽函数实现;
1 void MainWindow::on_pushButton_2_clicked()
2 {
3 QString filename1 = QFileDialog::getSaveFileName(this,tr("Save Image"),"",tr("Images (*.png *.bmp *.jpg)")); //选择路径
4 QScreen *screen = QGuiApplication::primaryScreen();
5 screen->grabWindow(ui->label->winId()).save(filename1);
6 }
保存按钮槽函数实现;
1 void MainWindow::on_pushButton_3_clicked()
2 {
3 QScreen *screen = QGuiApplication::primaryScreen();
4 screen->grabWindow(ui->label->winId()).save(QString("%1/34.jpg").arg(hglpPath));
5 }
原文：https://www.cnblogs.com/ybqjymy/p/13467911.html