Notes

#include<windows.h>
#include<stdio.h>
#include<GL/glut.h>
#define outcode int
double xmin=50,ymin=50,xmax=100,ymax=100;
double xvmin=200,yvmin=200,xvmax=300,yvmax=300;
const int RIGHT = 8;
const int LEFT = 2;
const int TOP = 4;
const int BOTTOM=1;

outcode ComputeOutCode(double x,double y);

void CohenSutherlandLineClipAndDraw(double x0,double y0,double x1,double y1)
{
outcode outcode0,outcode1,outcodeOut;
bool accept = false,done = false;
outcode0 = ComputeOutCode(x0,y0);
outcode1 = ComputeOutCode(x1,y1);

do
{
if(!(outcode0|outcode1))
{
accept = true;
done = true;
}
else if(outcode0 & outcode1)
done = true;
else
{
double x,y;
outcodeOut = outcode0? outcode0: outcode1;

if(outcodeOut & TOP)
{
x = x0 + (x1-x0) * (ymax - y0)/(y1-y0);
y = ymax;
}
else if(outcodeOut & BOTTOM)
{
x = x0 + (x1-x0) * (ymin - y0)/(y1-y0);
y = ymin;
}
else if(outcodeOut & RIGHT)
{
y = y0 + (y1-y0) * (xmax - x0)/(x1-x0);
x = xmax;
}
else
{
y = y0 + (y1-y0) * (xmin-x0)/(x1-x0);
x = xmin;
}

if(outcodeOut == outcode0)
{
x0 = x;
y0 = y;
outcode0 = ComputeOutCode(x0,y0);
}
else
{
x1 = x;
y1 = y;
outcode1 = ComputeOutCode(x1,y1);
}
}
}while(!done);

if(accept)
{
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();
}
}

outcode ComputeOutCode(double x,double y)
{
outcode code = 0;
if(y>ymax)
code |= TOP;
else if(y<ymin)
code |= BOTTOM;
if(x>xmax)
code |= RIGHT;
else if(x<xmin)
code |= LEFT;
return code;
}

void display()
{
double x0=120,y0=10,x1=40,y1=130;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0,0.0,0.0);
glBegin(GL_LINES);
glVertex2d(x0,y0);
glVertex2d(x1,y1);
glVertex2d(60,20);
glVertex2d(80,120);
glEnd();
glColor3f(0.0,0.0,1.0);
glBegin(GL_LINE_LOOP);
glVertex2f(xmin,ymin);
glVertex2f(xmax,ymin);
glVertex2f(xmax,ymax);
glVertex2f(xmin,ymax);
glEnd();
CohenSutherlandLineClipAndDraw(x0,y0,x1,y1);
CohenSutherlandLineClipAndDraw(60,20,80,120);
glFlush();
}
void myinit()
{
glClearColor(1.0,1.0,1.0,1.0);
glColor3f(1.0,0.0,0.0);
glPointSize(1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,499.0,0.0,499.0);
}
int main(int argc, char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(500,500);
glutInitWindowPosition(0,0);
glutCreateWindow("Cohen Sutherland Line Clipping Algorithm");
glutDisplayFunc(display);
myinit();
glutMainLoop();
}