QT软件开发: 截取全屏、指定位置、当前窗口保存图片

#include <QScreen>
#include <QTimer>
connect(&timer, SIGNAL(timeout()), this, SLOT(update()));
timer.start(50);

void Form::update()
{
    static int cnt=0;
    QScreen *screen = QGuiApplication::primaryScreen();
    //截取当前桌面全屏画面
    screen->grabWindow(0).save(QString("%1.jpg").arg(cnt++));
}

void Form::update()
{
    static int cnt=0;
    QScreen *screen = QGuiApplication::primaryScreen();
    QRect rect;
    rect.setX(this->mapToGlobal(this->pos()).x());
    rect.setY(this->mapToGlobal(this->pos()).y());
    rect.setWidth(this->width());
    rect.setHeight(this->height());
    screen->grabWindow(0,rect.x(),rect.y(),rect.width(),rect.height()).save(QString("%1.jpg").arg(cnt++));//截取当前桌面
}

void Form::update()
{
    //截取当前窗口画面.---不能透过窗口截后面
    this->grab().save(QString("%1.jpg").arg(cnt++));
}