Screen color picker

        When you encounter a nice background color and want to know its RGB value, you need a screen color picker. As follows, use the left mouse button to click the + character, drag to the color position you want to pick up, and release the left button to get the RGB value of that position.

        The Qt source code and exe tool link of this project
        uses Qt5.4.1 to write the code of the screen picker as follows:
//1) The header file myColor.h

#pragma once

#include <QtWidgets/QWidget>
#include "ui_myColor.h"


class QGridLayout;
class QVBoxLayout;
class QLabel;
class QLineEdit;

#if (QT_VERSION < QT_VERSION_CHECK(5,7,0))
#include <QtDesigner/QDesignerExportWidget>
#else
#include <QtUiPlugin/QDesignerExportWidget>
#endif


class myColor : public QWidget
{
    
    
	Q_OBJECT

public:
	static myColor *Instance();
	myColor(QWidget *parent = Q_NULLPTR);

protected:
	void mousePressEvent(QMouseEvent *);
	void mouseReleaseEvent(QMouseEvent *);

private:
	static myColor *instance;
	QClipboard *cp;
	bool pressed;
	QTimer *timer;

	QGridLayout *gridLayout;
	QVBoxLayout *verticalLayout;
	QLabel *labColor;
	QLabel *label;
	QLabel *labWeb;
	QLineEdit *txtWeb;
	QLabel *labRgb;
	QLineEdit *txtRgb;
	QLabel *labPoint;
	QLineEdit *txtPoint;

	private Q_SLOTS:
	void showColorValue();

private:
	Ui::myColorClass ui;
};

//2) Source file myColor.cpp

#pragma execution_character_set("utf-8")

#include "myColor.h"
#include <QBasicMutex>
#include <QGridLayout>
#include <QLabel>
#include <QLineEdit>
#include <QApplication>
#include <QMouseEvent>
#include <QTimer>
#include <QEvent>
#include <QDebug>
#include <QScreen>
#include <qdesktopwidget.h>

myColor *myColor::instance = 0;
myColor *myColor::Instance()
{
    
    
	if (!instance)
	{
    
    
		static QMutex mutex;
		QMutexLocker locker(&mutex);
		if (!instance)
		{
    
    
			instance = new myColor;
		}
	}
	
	return instance;
}


myColor::myColor(QWidget *parent)
	: QWidget(parent)
{
    
    
	gridLayout = new QGridLayout(this);
	gridLayout->setSpacing(6);
	gridLayout->setContentsMargins(11, 11, 11, 11);

	verticalLayout = new QVBoxLayout();
	verticalLayout->setSpacing(0);

	labColor = new QLabel(this);
	labColor->setText("+");
	labColor->setStyleSheet("background-color: rgb(255, 107, 107);color: rgb(250, 250, 250);");
	labColor->setAlignment(Qt::AlignCenter);
	QFont font;
	font.setPixelSize(35);
	font.setBold(true);
	labColor->setFont(font);

	QSizePolicy sizePolicy(QSizePolicy::Preferred, QSizePolicy::Expanding);
	sizePolicy.setHorizontalStretch(0);
	sizePolicy.setVerticalStretch(0);
	sizePolicy.setHeightForWidth(labColor->sizePolicy().hasHeightForWidth());
	labColor->setSizePolicy(sizePolicy);
	labColor->setMinimumSize(QSize(80, 70));
	labColor->setMaximumSize(QSize(80, 70));
	labColor->setCursor(QCursor(Qt::CrossCursor));
	labColor->setFrameShape(QFrame::StyledPanel);
	labColor->setFrameShadow(QFrame::Sunken);

	verticalLayout->addWidget(labColor);

	label = new QLabel(this);
	label->setMinimumSize(QSize(0, 18));
	label->setStyleSheet("background-color: rgb(0, 0, 0);color: rgb(200, 200, 200);");
	label->setAlignment(Qt::AlignCenter);

	verticalLayout->addWidget(label);
	gridLayout->addLayout(verticalLayout, 0, 0, 3, 1);

	labWeb = new QLabel(this);
	gridLayout->addWidget(labWeb, 0, 1, 1, 1);

	txtWeb = new QLineEdit(this);
	gridLayout->addWidget(txtWeb, 0, 2, 1, 1);

	labRgb = new QLabel(this);
	gridLayout->addWidget(labRgb, 1, 1, 1, 1);

	txtRgb = new QLineEdit(this);
	gridLayout->addWidget(txtRgb, 1, 2, 1, 1);

	labPoint = new QLabel(this);
	gridLayout->addWidget(labPoint, 2, 1, 1, 1);

	txtPoint = new QLineEdit(this);
	gridLayout->addWidget(txtPoint, 2, 2, 1, 1);

	label->setText("当前颜色显示");
	labWeb->setText("web值:");
	labRgb->setText("rgb值:");
	labPoint->setText("坐标值:");

	this->setLayout(gridLayout);
	this->setWindowTitle("屏幕拾色器");
	this->setFixedSize(270, 108);

	cp = QApplication::clipboard();
	pressed = false;

	timer = new QTimer(this);
	timer->setInterval(100);
	connect(timer, SIGNAL(timeout()), this, SLOT(showColorValue()));
	timer->start();

	ui.setupUi(this);
}

void myColor::mousePressEvent(QMouseEvent *e)
{
    
    
	if (labColor->rect().contains(e->pos()))
	{
    
    
		pressed = true;
	}
}

void myColor::mouseReleaseEvent(QMouseEvent *e)
{
    
    
	pressed = false;
}

void myColor::showColorValue()
{
    
    
	if (!pressed)
	{
    
    
		return;
	}

	int x = QCursor::pos().x();
	int y = QCursor::pos().y();

	txtPoint->setText(tr("x:%1  y:%2").arg(x).arg(y));
	QString strDecimalValue, strHex, strTextColor;
	int red, green, blue;

#if (QT_VERSION <= QT_VERSION_CHECK(5,0,0))
	QPixmap pixmap = QPixmap::grabWindow(QApplication::desktop()->winId(), x, y, 2, 2);
#else
	QScreen *screen = QApplication::primaryScreen();
	QPixmap pixmap = screen->grabWindow(QApplication::desktop()->winId(), x, y, 2, 2);
#endif

	if (!pixmap.isNull()) {
    
    
		QImage image = pixmap.toImage();

		if (!image.isNull()) {
    
    
			if (image.valid(0, 0)) {
    
    
				QColor color = image.pixel(0, 0);
				red = color.red();
				green = color.green();
				blue = color.blue();
				QString strRed = tr("%1").arg(red & 0xFF, 2, 16, QChar('0'));
				QString strGreen = tr("%1").arg(green & 0xFF, 2, 16, QChar('0'));
				QString strBlue = tr("%1").arg(blue & 0xFF, 2, 16, QChar('0'));

				strDecimalValue = tr("%1, %2, %3").arg(red).arg(green).arg(blue);
				strHex = tr("#%1%2%3").arg(strRed.toUpper()).arg(strGreen.toUpper()).arg(strBlue.toUpper());
			}
		}
	}

	if (red > 200 && green > 200 && blue > 200) {
    
    
		strTextColor = "10, 10, 10";
	}
	else {
    
    
		strTextColor = "255, 255, 255";
	}

	QString str = tr("background-color: rgb(%1);color: rgb(%2)").arg(strDecimalValue).arg(strTextColor);
	labColor->setStyleSheet(str);
	txtRgb->setText(strDecimalValue);
	txtWeb->setText(strHex);

}