openglpru1

#include <GL/glut.h>
#include <GL/gl.h>
 double X1, Y1, X2, Y2;

float round_value(float v)
{
  return floor(v + 0.5);
}
void LineDDA(void)
{
  double dx=(X2-X1);
  double dy=(Y2-Y1);
  double steps;
  float xInc,yInc,x=X1,y=Y1;

  steps=(abs(dx)>abs(dy))?(abs(dx)):(abs(dy));
  xInc=dx/(float)steps;
  yInc=dy/(float)steps;


  glClear(GL_COLOR_BUFFER_BIT);


  glBegin(GL_POINTS);

  glVertex2d(x,y);
  int k;

  for(k=0;k<steps;k++)
  {
    x+=xInc;
    y+=yInc;

    glVertex2d(round_value(x), round_value(y));
  }
  glEnd();

  glFlush();
}
void Init()
{

  glClearColor(1.0,1.0,1.0,0);

  glColor3f(0.0,0.0,0.0);

  gluOrtho2D(0 , 640 , 0 , 480);
}
int main(int argc, char **argv)
{
         printf("Enter two end points of the line to be drawn:\n");

  printf("\nEnter Point1( X1 , Y1):\n");
  scanf("%lf%lf",&X1,&Y1);

  printf("\nEnter Point1( X2 , Y2):\n");
  scanf("%lf%lf",&X2,&Y2);


  glutInit(&argc,argv);

  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

  glutInitWindowPosition(0,0);
  glutInitWindowSize(640,480);

  glutCreateWindow("DDA_Line");

  Init();

  glutDisplayFunc(LineDDA);

  glutMainLoop();
}