DDA.cpp

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
#include<GL/glut.h>
#include<math.h>

#define ROUND(x)((int)(x+0.5))
using namespace std;

int x1,x2,z1,z2;

void draw_pixel(int x, int y)
{
    glColor3f(1.0,0.0,0.0);
    glBegin(GL_POINTS);
    glVertex2i(x,y);
    glEnd();
}

void drawline(int X1, int Y1, int X2, int Y2)
{
    float x,y,dx,dy,length; int i;

    dx=abs(X2-X1);
    dy=abs(Y2-Y1);

    if(dx>=dy)
    length=dx;

    else length=dy;
    dx=(X2-X1)/length;
    dy=(Y2-Y1)/length;

    x=X1;
    y=Y1;
    i=1;

    while(i<=length)
    {
        draw_pixel(ROUND(x),ROUND(y));
        x=x+dx;
        y=y+dy;
        i=i+1;
    }
    glFlush();
}

void drawpatt(int ax, int ay, int bx, int by, int cx, int cy, int dx, int dy, int n)
{
    int m1x, m1y, m2x, m2y, m3x, m3y, m4x, m4y;

    drawline(ax,ay,bx,by);
    drawline(bx,by,cx,cy);
    drawline(cx,cy,dx,dy);
    drawline(dx,dy,ax,ay);

    //midpoint calculations;
    m1x=(ax+bx)/2;
    m1y=(ay+by)/2;
    m2x=(bx+cx)/2;
    m2y=(by+cy)/2;
    m3x=(cx+dx)/2;
    m3y=(cy+dy)/2;
    m4x=(dx+ax)/2;
    m4y=(dy+ay)/2;
    n--; if(n!=0)
    {
        drawpatt(m1x, m1y, m2x, m2y, m3x, m3y, m4x, m4y,n);
    }
}

void display(void)
{
    float x,y,dx,dy,length;

    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0,0.0,0.0);
    glBegin(GL_LINES);
    glVertex2i(-200,0);
    glVertex2i(200,0);
    glVertex2i(0,-200);
    glVertex2i(0,200);

    glEnd();
    drawpatt(x1,z1,x1,z2,x2,z2,x2,x1,5);
}

void Init(void)
{
    glClearColor(1,1,1,0);
    gluOrtho2D(-200.0,200.0,-200.0,200.0);
}

int main(int argc, char **argv)
{
    /* cout<<"\n Enter the value of left bottom x1::"; cin<<x1;
    cout<<"\n Enter the value of left bottom y1:"; cin<<y1;
    cout<<"\n Enter the value of right top x2:"; cin<<x2;
    cout<<"\n Enter the value of right top y2:"; cin<<y2; */
    printf("Enter the value of left bottom x1:");
    scanf("%d",&x1);    

    printf("Enter the value of left bottom y1:");
    scanf("%d",&z1);

    printf("Enter the value of right top x2:");
    scanf("%d",&x2);

    printf("Enter the value of right top y2:");
    scanf("%d",&z2);

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

    glutInitWindowSize(500,500);
    glutInitWindowPosition(100,100);

    glutCreateWindow("Pattern Drawing");
    Init();
    glClear(GL_COLOR_BUFFER_BIT);
    glutDisplayFunc(display);
    glFlush();
    glutMainLoop();

    return 0;
}