term2.c

#include<stdio.h>
#include<GL/glut.h>
double xmin=50,ymin=50,xmax=100,ymax=100;
double xvmin=200,yvmin=200,xvmax=300,yvmax=300;
double x0,y0,x1,y1;

int cliptest(double p,double q,double *t1,double *t2)
{
	double t=q/p;
	if(p<0.0)
	{
		if(t > *t1) *t1=t;
		if(t > *t2) return(0);
	}
	else if(p>0.0)
	{
		if(t< *t2) *t2=t;
		if(t< *t1) return(0);
	}
	else if(p==0.0)
	{
		if(q<0.0) return(0);
	}
	return(1);
}
void LiangBarsky(double x0,double y0,double x1,double y1)
{
	double dx=x1-x0,dy=y1-y0,te=0.0,tl=1.0;
	if(cliptest(-dx,x0-xmin,&te,&tl));
	if(cliptest(dx,xmax-x0,&te,&tl));
	if(cliptest(-dy,y0-ymin,&te,&tl));
	if(cliptest(dy,ymax-y0,&te,&tl));
	{
		if(tl<1.0)
		{
			x1=x0+tl*dx;
			y1=y0+tl*dy;
		}
		if(te>0.0)
		{
			x0=x0+te*dx;
			y0=y0+te*dy;
		}
		double sx=(xvmax-xvmin)/(xmax-xmin);
		double sy=(yvmax-yvmin)/(ymax-ymin);
		double vx0=xvmin+(x0-xmin)*sx;
		double vy0=yvmin+(y0-ymin)*sy;
		double vx1=xvmin+(x1-xmin)*sx;
		double vy1=yvmin+(y1-ymin)*sy;
		
		glColor3f(1.0,0.0,0.0);
		glBegin(GL_LINE_LOOP);
			glVertex2f(xvmin,yvmin);
			glVertex2f(xvmax,yvmin);
			glVertex2f(xvmax,yvmax);
			glVertex2f(xvmin,yvmax);

		glEnd();
		glColor3f(0.0,0.0,1.0);
		glBegin(GL_LINES);
			glVertex2d(vx0,vy0);
			glVertex2d(vx1,vy1);
		glEnd();
	}
}
void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(0.0,0.0,1.0);
	glBegin(GL_LINES);
	glVertex2d(x0,y0);
	glVertex2d(x1,y1);
	glEnd();
	glColor3f(1.0,0.0,0.0);
	glBegin(GL_LINE_LOOP);
		glVertex2f(xmin,ymin);
		glVertex2f(xmax,ymin);
		glVertex2f(xmax,ymax);
		glVertex2f(xmin,ymax);
	glEnd();
	LiangBarsky(x0,y0,x1,y1);
	glFlush();
}
void myinit()
{
	glClearColor(1.0,1.0,1.0,1.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0,499.0,0.0,499.0);
}
void main(int argc,char** argv)
{
	printf("Enter the end points of the line: ");
	scanf("%lf %lf %lf %lf",&x0,&y0,&x1,&y1);
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(0,0);
	glutCreateWindow("2nd Program");
	glutDisplayFunc(display);
	myinit();
	glutMainLoop();
}