QT编写简易截图工具

Windows和Linux下编译通过，版本5.9.1

##设计界面
新建Widget项目，进入ui设计界面，添加QLabel和两个QPushButton，布局如下：

Button重命名为pushButton_save和pushButton_snip。
加入menu如下，添加action并设置快捷键。

##创建截图窗口类

Markdown及扩展

添加新文件，选择QT Designer Form Class，如下，继承QWidget，类名修改为ScreenShot，作为截图窗口类。

##添加代码
转到mainwindow.h在类中添加重绘事件函数：

mainwindow.h

protected:void paintEvent(QPaintEvent *);

另外添加按钮和菜单的槽函数：

mainwindow.h

private slots:void on_actionSave_triggered();void on_actionCopy_triggered();void on_pushButton_snip_clicked();void on_pushButton_save_clicked();void on_actionSnip_triggered();void timerSlot();                   //定时器处理槽函数void screenShotHideSlot();          //截图窗口消失槽函数

添加成员变量：（注意要加入头文件#include screenshot.h 和 QTimer）

mainwindow.h

private:Ui::MainWindow *ui;ScreenShot *wScreen;     //截图窗口类QTimer timer;           //定时器QPixmap tmpPix;         //用于保存截图的临时变量

转到mainwindow.cpp实现成员函数
首先添加所需要用到的头文件：

mainwindow.cpp

#include "screenshot.h"
#include <QDesktopWidget>
#include <QPainter>
#include <QPixmap>
#include <QFileDialog>
#include <QMessageBox>
#include <QTimer>
#include <QClipboard>

再在构造函数中添加如下代码：

mainwindow.cpp

    this->setWindowTitle(tr("截图工具"));wScreen = new ScreenShot;wScreen->hide();     //初始化不显示QDesktopWidget *deskWidget = QApplication::desktop();QRect deskRect = deskWidget->geometry();            //获取桌面大小resize(deskRect.width() / 3, deskRect.height() / 3);//设置窗口大小connect(&timer,SIGNAL(timeout()),this,SLOT(timerSlot()));

然后分别实现其他成员函数如下：

mainwindow.cpp

//Snip按钮槽函数
void MainWindow::on_pushButton_snip_clicked()
{this->hide();   //截图开始 隐藏主窗口timer.start(20);//这里加定时器是因为窗口不会立即隐藏
}
//重绘事件函数
void MainWindow::paintEvent(QPaintEvent *)
{if(tmpPix.isNull() == false)    //若截图不为空{//将截图大小缩放到label大小 可看scaled的帮助文档QPixmap scalePix = tmpPix.scaled(ui->label->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);//label显示截图ui->label->setPixmap(scalePix);}
}
//save按钮槽函数
void MainWindow::on_pushButton_save_clicked()
{if(tmpPix.isNull() == false)    //若截图不为空{//打开保存文件对话框QString fileName = QFileDialog::getSaveFileName(this,"save","../",tr("Images (*.png *.xpm *.jpg)"));//保存截图tmpPix.save(fileName);}else{QMessageBox::information(this,"warning","no screenshot");}
}
//定时器处理函数
void MainWindow::timerSlot()
{//首先关闭定时器timer.stop();//获取屏幕的PixmapQPixmap screen = QPixmap::grabWindow(QApplication::desktop()->winId());//绑定截图窗口关闭信号与主窗口处理槽函数connect(wScreen,SIGNAL(closeSignal()),this,SLOT(screenShotHideSlot()));//截图窗口截取屏幕wScreen->shotScreen(screen);//显示截图窗口wScreen->show();
}
//截图窗口消失处理槽函数
void MainWindow::screenShotHideSlot()
{//显示主窗口this->show();//获取截图tmpPix = wScreen->getShotPixmap();//label显示截图QPixmap scalePix = tmpPix.scaled(ui->label->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);ui->label->setPixmap(scalePix);
}
//菜单action函数
void MainWindow::on_actionSnip_triggered()
{on_pushButton_snip_clicked();
}void MainWindow::on_actionSave_triggered()
{on_pushButton_save_clicked();
}void MainWindow::on_actionCopy_triggered()
{if(tmpPix.isNull() == true){QMessageBox::information(this,"warning","no image");return;}QClipboard *clipboard = QApplication::clipboard();clipboard->setImage(tmpPix.toImage());
}

有部分函数需要在截图窗口类ScreenShot类中实现，现在实现该类，转到screenshot.h中，添加所需头文件：

screenshot.h

#include <QPixmap>
#include <QTimer>

再添加如下成员函数和变量：

screenshot.h

public:void shotScreen(QPixmap &pix);QPixmap snipScreen(QPixmap &pix,QPoint &start,QPoint &end);QPixmap& getShotPixmap();signals:void closeSignal();protected:void paintEvent(QPaintEvent *);void mousePressEvent(QMouseEvent *e);void mouseMoveEvent(QMouseEvent *e);void mouseReleaseEvent(QMouseEvent *);private:QPoint startPoint;QPoint endPoint;QPixmap screen;QPixmap shotPix;QTimer timer;

转到screenshot.cpp实现成员函数：
添加所需头文件：

screenshot.cpp

#include <QPainter>
#include <QPixmap>
#include <QMouseEvent>
#include <QMessageBox>

在构造函数中加入：

    //设置窗口没有标题栏this->setWindowFlags(Qt::FramelessWindowHint);//定时器信号和槽connect(&timer,SIGNAL(timeout()),this,SLOT(update()));

其他函数：

screenshot.cpp

//设置截图窗口
void ScreenShot::shotScreen(QPixmap &screenPix)
{this->screen = screenPix;//设置窗口大小 和屏幕大小一致this->resize(screenPix.size());//设置遮罩this->setMask(QRegion(0,0,width(),height()));
}//绘图事件函数
void ScreenShot::paintEvent(QPaintEvent *)
{QPainter painter(this);painter.drawPixmap(0,0,screen);//设置画笔样式QPen pen;pen.setStyle(Qt::DashLine);pen.setColor(Qt::red);painter.setPen(pen);//所需截图区域用矩形框显示painter.drawRect(QRect(startPoint,endPoint));
}//鼠标事件函数
void ScreenShot::mousePressEvent(QMouseEvent *e)
{if(e->button() == Qt::LeftButton){//鼠标左键按下 设置起始点timer.start(20);startPoint = e->pos();endPoint = startPoint;}else if(e->button() == Qt::RightButton){//鼠标右键按下 隐藏截图窗口 并向主窗口发送关闭消息hide();emit closeSignal();}
}void ScreenShot::mouseMoveEvent(QMouseEvent *e)
{if(e->buttons() & Qt::LeftButton){endPoint = e->pos();}
}void ScreenShot::mouseReleaseEvent(QMouseEvent *e)
{endPoint = e->pos();if(QMessageBox::Yes == QMessageBox::question(this,"question","yes to shot?")){shotPix = snipScreen(screen,startPoint,endPoint);this->hide();startPoint = QPoint(0,0);endPoint = startPoint;emit closeSignal();}
}//截图函数
QPixmap ScreenShot::snipScreen(QPixmap &pix, QPoint &start, QPoint &end)
{int w = abs(start.x() - end.x());int h = abs(start.y() - end.y());QPixmap tmp = QPixmap(w,h);QPainter painter(&tmp);//将截图部分绘制到tmp中painter.drawPixmap(QPoint(0,0),pix,QRect(start,end));return tmp;
}//获取截图函数
QPixmap& ScreenShot::getShotPixmap()
{return shotPix;
}

##编译运行
最后编译运行结果如下：

点击按钮就可以单击鼠标左键拖动截图。
附源码下载： http://download.csdn.net/download/weddyhuo/10124652