QT截屏，截取控件为图片，指定范围截屏三种截屏方式

项目中我们常用到截取屏幕，Qt给我的们多种方式：

主要有以下三种：

截取全屏；截取控件为图片；指定位置截屏三种截屏方式；

1.截取全屏

常用：

实现：

    QScreen *screen = QGuiApplication::primaryScreen();

   screen->grabWindow(0).save("./picture.png", "png");

2.截取控件为图片

 实现：

    QScreen *screen = QGuiApplication::primaryScreen();
    auto rect =  ui->calendarWidget->rect();
 
    auto widgetScreenPic = screen->grabWindow(ui->calendarWidget->winId(), rect.x(), rect.y(), rect.width(), rect.height());
    widgetScreenPic = widgetScreenPic.scaled(QSize(rect.width(), rect.height()), Qt::KeepAspectRatio);

    widgetScreenPic.save("./widgetpicture.png");

 上面这种方式对造成我的布局显示有问题，改为在全屏上截取控件的范围

    QScreen *screen = QGuiApplication::primaryScreen();
    auto rect =  ui->calendarWidget->rect();
    QPoint globalPos = ui->calendarWidget->mapToGlobal(QPoint(0, 0));
    //auto widgetScreenPic = screen->grabWindow(ui->calendarWidget->winId(), rect.x(), rect.y(), rect.width(), rect.height());

    auto widgetScreenPic = screen->grabWindow(0, globalPos.x(), globalPos.y(), rect.width(), rect.height());
    widgetScreenPic = widgetScreenPic.scaled(QSize(rect.width(), rect.height()), Qt::KeepAspectRatio);

    widgetScreenPic.save("./widgetpicture.png");

3.指定范围截屏：

实现：

       QPixmap p = this->grab(QRect(-20, -20, 200, 500));

       p.save("./Rectpicture.png","png");