qt 自定义颜色选择器

在右边选择颜色，左侧的QLable  背景色会跟着变化 

核心难点：

    通过鼠标点击的坐标， 获取点击的颜色值。

void MyColorWidget::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);

    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);

    rectColor = QRect(0,0,this->width(),this->height());

    QLinearGradient linearGradient(0,0,0,this->height());
    linearGradient.setColorAt(0, Qt::red);
    linearGradient.setColorAt(0.2, Qt::yellow);
    linearGradient.setColorAt(0.4, Qt::green);
    linearGradient.setColorAt(0.6, Qt::blue);
    linearGradient.setColorAt(0.8, Qt::black);
    linearGradient.setColorAt(1, Qt::white);
    painter.setBrush(QBrush(linearGradient));

    painter.setPen(QPen(Qt::black,1));
    painter.drawRect(rectColor);
}

void MyColorWidget::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton)
    {
        this->setFocus();
        QPoint point = event->pos();

        getPointColor(point);

        emit choicesColor(myColor);
    }
}

void MyColorWidget::mouseMoveEvent(QMouseEvent *event)
{
    if(Qt::LeftButton == (event->buttons() & Qt::LeftButton))
    {
        QPoint point = event->pos();

        getPointColor(point);

        emit choicesColor(myColor);
    }
}

void MyColorWidget::getPointColor(const QPoint &point)
{
    // 通过抓屏，获取某一点的颜色
    if(rectColor.contains(point))
    {
        QPoint deskPoint = mapToGlobal(point);   // 转换为桌面坐标

        // 抓屏，截取一个像素的图片
        QScreen *m_screen = this->window()->windowHandle()->screen();
        QPixmap pixmap = m_screen->grabWindow(QApplication::desktop()->winId(), deskPoint.x(), deskPoint.y(), 1, 1);
        if (!pixmap.isNull())
        {
            QImage image = pixmap.toImage();
            if (!image.isNull())
            {
                myColor = image.pixel(0, 0);

                int m_red = myColor.red();
                int m_green = myColor.green();
                int m_blue = myColor.blue();

                rgbStr = QString("%1, %2, %3").arg(m_red).arg(m_green).arg(m_blue);

                update();
            }

           delete ℑ
        }

        delete &pixmap;
    }
}

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