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");