16. Graphics Program to demonstrate Line Clipping.

#include <GL/gl.h>
#include <GL/glut.h>
#include <math.h>
#include <stdio.h>
void display();
float xmin=-100;
float ymin=-100;
float xmax=100;
float ymax=100;
float xd1,yd1,xd2,yd2;
void init(void)
{
glClearColor(0.0,0,0,0);
glMatrixMode(GL_PROJECTION);
gluOrtho2D(-300,300,-300,300);
}
int code(float x,float y)
{
int c=0;
if(y>ymax) c=8;
if(y<ymin) c=4;
if(x>xmax) c=c|2;
if(x<xmin) c=c|1;
return c;
}
void cohen_Line(float x1,float y1,float x2,float y2)
{
int c1=code(x1,y1);
int c2=code(x2,y2);
float m=(y2-y1)/(x2-x1);
while((c1|c2)>0)
{
if((c1&c2)>0){
exit(0);
}
float xi=x1;
float yi=y1;
int c=c1;

if(c==0)
{
c=c2;
xi=x2;
yi=y2;
}
float x,y;
if((c&8)>0)
{
y=ymax;
x=xi+1.0/m*(ymax-yi);
}
else
if((c&4)>0)
{
y=ymin;
x=xi+1.0/m*(ymin-yi);
}
else
if((c&2)>0)
{
x=xmax;
y=yi+m*(xmax-xi);
}
else
if((c&1)>0)
{
xmin;
y=yi+m*(xmin-xi);
}
if(c==c1)
{
xd1=x;
yd1=y;
c1=code(xd1,yd1);
}

if(c==c2)
{
xd2=x;
yd2=y;
c2=code(xd2,yd2);
}
}
display();
}
void myKey(unsigned char key,int x,int y)
{
if(key=='c')
{
printf("Hello");
cohen_Line(xd1,yd1,xd2,yd2);
glFlush();
}
}
void display()
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0,1.0,0.0);
glBegin(GL_LINE_LOOP);
glVertex2i(xmin,ymin);
glVertex2i(xmin,ymax);
glVertex2i(xmax,ymax);
glVertex2i(xmax,ymin);
glEnd();
glColor3f(1.0,0.0,0.0);
glBegin(GL_LINES);
glVertex2i(xd1,yd1);
glVertex2i(xd2,yd2);
glEnd();
glFlush();
}

int main(int argc,char** argv)
{
printf("Enter line co-ordinates:");
scanf("%f %f %f %f",&xd1,&yd1,&xd2,&yd2);
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(600,600);
glutInitWindowPosition(0,0);
glutCreateWindow("Clipping");
glutDisplayFunc(display);
glutKeyboardFunc(myKey);
init();
glutMainLoop();
return 0;
}