Drawing a Line with Different Line Styles

Q:Write a program in C++ to draw a line with different styles thick, thin and dotted. Accept the start point and end point coordinates from the user.

Framework used:- QT
Platfrom :-Cross-platfrom(Linux/Windows)

The algorithm used to draw the line is dda algorithm
Code:-
(For code for other classes and files. See download link below)
mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <algorithm>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}
inline int MainWindow::sign(float num){
    return ((num<0)?-1:(num>0));
}
void MainWindow::on_pushButton_2_clicked()  //code for thin line
{
    int x1=ui->lineEdit->text().toInt();
    int y1=ui->lineEdit_2->text().toInt();
    int x2=ui->lineEdit_3->text().toInt();
    int y2=ui->lineEdit_4->text().toInt();
    QImage image(500,500,QImage::Format_RGB888);
    QRgb value;
    value=qRgb(0,255,0);
    int length=std::max(abs(x2-x1),abs(y2-y1));
    float dx=(x2-x1)/(float)length;
    float dy=(y2-y1)/(float)length;
    float x=x1+0.5*sign(dx);
    float y=y1+0.5*sign(dy);
    int i=1;
    for(i=1;i<=length;i++){
        image.setPixel(int(x),int(y),value);
        x=dx+x;
        y=y+dy;
    }
    ui->label_5->setPixmap(QPixmap::fromImage(image));

}

void MainWindow::on_pushButton_4_clicked()      //code for dotted line
{
    int x1=ui->lineEdit->text().toInt();
    int y1=ui->lineEdit_2->text().toInt();
    int x2=ui->lineEdit_3->text().toInt();
    int y2=ui->lineEdit_4->text().toInt();
    QImage image(500,500,QImage::Format_RGB888);
    QRgb value;
    value=qRgb(0,255,0);
    int length=std::max(abs(x2-x1),abs(y2-y1));
    float dx=(x2-x1)/(float)length;
    float dy=(y2-y1)/(float)length;
    float x=x1+0.5*sign(dx);
    float y=y1+0.5*sign(dy);
    int i=1;
    for(i=1;i<=length;i=i+2){
        image.setPixel(int(x),int(y),value);
        x=dx*2+x;
        y=y+dy*2;
    }
    ui->label_5->setPixmap(QPixmap::fromImage(image));
}

void MainWindow::on_pushButton_3_clicked()
{
    int x1=ui->lineEdit->text().toInt();
    int y1=ui->lineEdit_2->text().toInt();
    int x2=ui->lineEdit_3->text().toInt();
    int y2=ui->lineEdit_4->text().toInt();
    QImage image(500,500,QImage::Format_RGB888);
    QRgb value;
    value=qRgb(0,200,0);
    int length=std::max(abs(x2-x1),abs(y2-y1));
    float dx=(x2-x1)/(float)length;
    float dy=(y2-y1)/(float)length;
    float x=x1+0.5*sign(dx);
    float y=y1+0.5*sign(dy);
    int i=1;
    int t,t2;
    for(i=1;i<=length;i++){
        for(t=-1;t<=1;t++){
            for(t2=-1;t2<=1;t2++){
                image.setPixel(int(x+t),int(y+t2),value);
            }
        }
        x=dx+x;
        y=y+dy;
    }
    ui->label_5->setPixmap(QPixmap::fromImage(image));
}

void MainWindow::on_pushButton_clicked()
{
    ui->lineEdit->setText("");
    ui->lineEdit_2->setText("");
    ui->lineEdit_3->setText("");
    ui->lineEdit_4->setText("");
    QImage image(500,500,QImage::Format_RGB888);
    ui->label_5->setPixmap(QPixmap::fromImage(image));
}

For all the files including screenshot related to this code click here:- mediafire 

Screenshot:-