Display a Pixel in Qt Creator C++

pixel.h file:

#ifndef PIXEL_H
#define PIXEL_H

#include <QMainWindow>

namespace Ui {
class pixel;
}

class pixel : public QMainWindow
{
    Q_OBJECT
    
public:
    explicit pixel(QWidget *parent = 0);
    ~pixel();
    
private:
    Ui::pixel *ui;
private slots:
   void draw();
};

#endif // PIXEL_H
-----------------------------------------------------------------
pixel.cpp file:
#include "pixel.h"
#include "ui_pixel.h"

pixel::pixel(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::pixel)
{
    ui->setupUi(this);
    connect(this->ui->pushButton,SIGNAL(clicked()),this,SLOT(draw()));
//Function connects
}


pixel::~pixel()
{
    delete ui;
}

void pixel::draw()
{
    int x1,y1;
    x1=this->ui->textEdit->toPlainText().toInt(); //x-coordinate 
    y1=this->ui->textEdit_2->toPlainText().toInt();//y-coordinate
    QRgb value;                    // RGB value
    value= qRgb(255,255,0);
    QImage q(400,400,QImage::Format_RGB32);
    q.setPixel(x1,y1,value);
    this->ui->label_3->setPixmap(QPixmap::fromImage(q));
}

Output