Notes

#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;
const int RIGHT = 8;
const int LEFT = 2;
const int TOP = 4;
const int BOTTOM = 1;
int ComputeOutCode (double x, double y)
{
int code = 0;
if (y > ymax) //above the clip window
code |= TOP;
else if (y < ymin) //below the clip window
code |= BOTTOM;
if (x > xmax) //to the right of clip window
code |= RIGHT;
else if (x < xmin) //to the left of clip window
code |= LEFT;
return code;
}
void CohenSutherland(double x0, double y0,double x1, double y1)
{
int 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, 1.0, 1.0);
glBegin(GL_LINE_LOOP);
glVertex2f(xvmin, yvmin);
glVertex2f(xvmax, yvmin);
glVertex2f(xvmax, yvmax);
glVertex2f(xvmin, yvmax);
glEnd();
glColor3f(1.0,1.0,1.0);
glBegin(GL_LINES);
glVertex2d (vx0, vy0);
glVertex2d (vx1, vy1);
glEnd();
}
}
void display()
{
double x0=60,y0=20,x1=80,y1=120;
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0,1.0,1.0);
glBegin(GL_LINES);
glVertex2d (x0, y0);
glVertex2d (x1, y1);
glEnd();
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_LINE_LOOP);
glVertex2f(xmin, ymin);
glVertex2f(xmax, ymin);
glVertex2f(xmax, ymax);
glVertex2f(xmin, ymax);
glEnd();
CohenSutherland(x0,y0,x1,y1);
glFlush();
}
void myinit()
{
glClearColor(0.0,0.0,0.0,1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,500.0,0.0,500.0);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);

glutInitWindowSize(500,500);
glutInitWindowPosition(0,0);
glutCreateWindow("Cohen Suderland Line Clipping Algorithm");
myinit();
glutDisplayFunc(display);
glutMainLoop();
}