test.cpp

#include <GL/glu.h>
#include <GL/freeglut.h>
#include <iostream>
#include <math.h>
#include<stdlib.h>
#include<stdio.h>
using namespace std;
#define ROUND(x) ((int)(x+0.5))
int xa,xb,ya,yb; 
void display (void)
 {
 int dx=xb-xa,dy=yb-ya,steps,k;
 float xIncrement,yIncrement,x=xa,y=ya;
 glClear (GL_COLOR_BUFFER_BIT);
 glColor3f (1.0, 0.0, 0.0);
 if(abs(dx)>abs(dy))
 steps=abs(dx);
 else steps=abs(dy);
 xIncrement=dx/(float)steps;
 yIncrement=dy/(float)steps;
 glBegin(GL_POINTS);
 glVertex2s(ROUND(x),ROUND(y));
for(k=0;k<steps;k++)
 {
 x+=xIncrement;
 y+=yIncrement;
 glVertex2s(ROUND(x),ROUND(y));
 printf("%lf %lf\n",x,y);
 }
 glColor3f (1.0, 1.0, 1.0);
 for(int i=-100 ; i<=100 ; i++)
 {
 glVertex2s(i,0);
 glVertex2s(0,i);
 }
 for(int i=-2; i<=2 ; i++)
 {
 glVertex2s(95+i,4+i);
 glVertex2s(95-i,4+i);
 } 
 for(int i=0; i<=2 ; i++)
 {
 glVertex2s(4+i,95+i);
 glVertex2s(4-i,95+i);
 glVertex2s(4,95-i);
 }

 glEnd();
 glFlush();
 }
 void init(void)
 {
 glClearColor (0.0, 0.0, 0.0, 0.0);
 glOrtho(-100.0, 100.0, -100.0, 100.0, -1.0, 1.0);
 }

int main(int argc, char** argv)
{
 printf("Enter the points\n");
 scanf("%d %d %d %d",&xa,&ya,&xb,&yb);
 glutInit(&argc, argv);
 glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
 glutInitWindowSize (500, 500);
 glutInitWindowPosition (100, 100);
 glutCreateWindow ("Simple DDA ");
 init ();
 glutDisplayFunc(display);
 glutMainLoop();
 return 0;
}