Qt实现对选中区域屏幕截图和窗口图像保存

// .cpp

#include "paintscreenshot.h"
#include <QApplication>
#include <QDesktopWidget>
#include <QMouseEvent>
#include <QWidget>
#include "screenshot.h"

PaintScreenshot::PaintScreenshot(QWidget *parent)
    : QWidget(parent)
    , m_bIsMousePress(false)
{
    initWindow();
    loadBackgroundPixmap();
}

PaintScreenshot::~PaintScreenshot()
{

}

void PaintScreenshot::initWindow()
{
    this->setMouseTracking(true);
    this->setWindowFlags(Qt::FramelessWindowHint);
    setWindowState(Qt::WindowActive | Qt::WindowFullScreen);
}

void PaintScreenshot::loadBackgroundPixmap()
{
    m_loadPixmap = QPixmap::grabWindow(QApplication::desktop()->winId()); //抓取当前屏幕的图片;
    m_nScreenwidth = m_loadPixmap.width();
    m_nScreenheight = m_loadPixmap.height();
}

void PaintScreenshot::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton)
    {
        m_bIsMousePress = true;
        m_beginPoint = event->pos();
    }

    return QWidget::mousePressEvent(event);
}

void PaintScreenshot::mouseMoveEvent(QMouseEvent* event)
{
    if (m_bIsMousePress)
    {
        m_endPoint = event->pos();
        update();
    }
    return QWidget::mouseMoveEvent(event);
}

void PaintScreenshot::mouseReleaseEvent(QMouseEvent *event)
{
    m_endPoint = event->pos();
    m_bIsMousePress = false;
    if (nullptr != m_pScreenshotWindow)
    {
        m_pScreenshotWindow->SendImageSaveAndShow(m_capturePixmap);
    }
    close();
    return QWidget::mouseReleaseEvent(event);
}

void PaintScreenshot::paintEvent(QPaintEvent *event)
{
    m_painter.begin(this);          //进行重绘;

    QColor mShadowColor = QColor(0, 0, 0, 100);                      //阴影颜色设置;
    m_painter.setPen(QPen(Qt::blue, 1, Qt::SolidLine, Qt::FlatCap));    //设置画笔;
    m_painter.drawPixmap(0, 0, m_loadPixmap);                       //将背景图片画到窗体上;
    m_painter.fillRect(m_loadPixmap.rect(), mShadowColor);           //画影罩效果;

    if (m_bIsMousePress)
    {
        QRect mSelectedRect = getRect(m_beginPoint, m_endPoint);
        m_capturePixmap = m_loadPixmap.copy(mSelectedRect);
        m_painter.drawPixmap(mSelectedRect.topLeft(), m_capturePixmap);
        m_painter.drawRect(mSelectedRect);
    }

    m_painter.end();  //重绘结束;
    return QWidget::paintEvent(event);
}

void PaintScreenshot::keyPressEvent(QKeyEvent *event)
{
    //// Esc 键退出截图;
    //if (event->key() == Qt::Key_Escape)
    //{
    //    close();
    //}
    // Eeter键完成截图;
    //if (event->key() == Qt::Key_Return || event->key() == Qt::Key_Enter)
    //{
    //    emit signalCompleteCature(m_capturePixmap);
    //    close();
    //}
    return QWidget::keyPressEvent(event);
}

QRect PaintScreenshot::getRect(const QPoint &beginPoint, const QPoint &endPoint)
{
    int x, y, nWidth, nHeight;
    nWidth = qAbs(beginPoint.x() - endPoint.x());
    nHeight = qAbs(beginPoint.y() - endPoint.y());
    x = beginPoint.x() < endPoint.x() ? beginPoint.x() : endPoint.x();
    y = beginPoint.y() < endPoint.y() ? beginPoint.y() : endPoint.y();

    QRect mSelectedRect = QRect(x, y, nWidth, nHeight);
    // 避免宽或高为零时拷贝截图有误;
    // 可以看QQ截图，当选取截图宽或高为零时默认为2;
    if (mSelectedRect.width() == 0)
    {
        mSelectedRect.setWidth(1);
    }
    if (mSelectedRect.height() == 0)
    {
        mSelectedRect.setHeight(1);
    }

    return mSelectedRect;
}

void PaintScreenshot::SendScreenshotWindowPoint(Screenshot * mScreenshotWindowPoint)
{
    if (nullptr != mScreenshotWindowPoint)
    {
        m_pScreenshotWindow = mScreenshotWindowPoint;
    }
}

// .h
#ifndef PAINTSCREENSHOT_H
#define PAINTSCREENSHOT_H

#include <QWidget>
#include <QScreen>
#include <QPainter>

class Screenshot;

class PaintScreenshot : public QWidget
{
public:
       PaintScreenshot(QWidget *parent = 0);
       ~PaintScreenshot();
       void SendScreenshotWindowPoint(Screenshot * );

private:
    void initWindow();
    void loadBackgroundPixmap();
    QRect getRect(const QPoint &mBeginPoint, const QPoint &mEndPoint);

    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent* event);
    void mouseReleaseEvent(QMouseEvent *event);
    void keyPressEvent(QKeyEvent *event);
    void paintEvent(QPaintEvent *event);

private:
    bool m_bIsMousePress;
    QPixmap m_loadPixmap, m_capturePixmap;
    int m_nScreenwidth;
    int m_nScreenheight;
    QPoint m_beginPoint, m_endPoint;
    QPainter m_painter;
    Screenshot * m_pScreenshotWindow;// 接收截图窗口的指针地址

};

#endif // PAINTSCREENSHOT_H