A C++ program for Liang Barsky line Clipping algorithm.


# include <iostream.h>
# include <graphics.h>
# include <conio.h>
# include <math.h>
//————————— LineCoordinates ————————-//
class LineCoordinates{
public:
float x_1,y_1,x_2,y_2;
LineCoordinates(const float x1,const float y1,const float x2,const float y2)
{
x_1=x1;
y_1=y1;
x_2=x2;
y_2=y2;
}};
//————————- WindowCoordinates ————————-//
class WindowCoordinates{
public:
float x_min,y_min,x_max,y_max;
WindowCoordinates(const float x1,const float y1,const float x2,const float y2){
x_min=x1;
y_min=y1;
x_max=x2;
y_max=y2;
}};
const int clip_line(const WindowCoordinates,LineCoordinates&);
const int check_line(const float,const float,float&,float&);
void Rectangle(const int,const int,const int,const int);
void Line(const int,const int,const int,const int);
//—————————— main( ) ——————————/
int main( )
{
int driver=VGA;
int mode=VGAHI;
initgraph(&driver,&mode,”..\\Bgi”);
WindowCoordinates WC(180,140,470,340);
setcolor(15);
Rectangle(WC.x_min,WC.y_min,WC.x_max,WC.y_max);
LineCoordinates LC_1(150,160,120,320);
LineCoordinates LC_2(250,150,200,200);
LineCoordinates LC_3(160,200,490,260);
LineCoordinates LC_4(300,300,400,380);
LineCoordinates LC_5(550,300,450,400);
LineCoordinates LC_6(440,110,400,370);
setcolor(7);
Line(LC_1.x_1,LC_1.y_1,LC_1.x_2,LC_1.y_2);
Line(LC_2.x_1,LC_2.y_1,LC_2.x_2,LC_2.y_2);
Line(LC_3.x_1,LC_3.y_1,LC_3.x_2,LC_3.y_2);
Line(LC_4.x_1,LC_4.y_1,LC_4.x_2,LC_4.y_2);
Line(LC_5.x_1,LC_5.y_1,LC_5.x_2,LC_5.y_2);
Line(LC_6.x_1,LC_6.y_1,LC_6.x_2,LC_6.y_2);
char Key=NULL;
do{
Key=getch( );
}while(Key!=’C’ && Key!=’c’);
settextstyle(0,0,1);
setcolor(0);
outtextxy(163,450,” Press ‘C’ to see the Clipped Lines. “);
setcolor(15);
outtextxy(163,450,”—— ——-“);
setcolor(12);
outtextxy(213,450,” Press any Key to exit. “);
setcolor(10);
if(clip_line(WC,LC_1))
Line(LC_1.x_1,LC_1.y_1,LC_1.x_2,LC_1.y_2);
if(clip_line(WC,LC_2))
Line(LC_2.x_1,LC_2.y_1,LC_2.x_2,LC_2.y_2);
if(clip_line(WC,LC_3))
Line(LC_3.x_1,LC_3.y_1,LC_3.x_2,LC_3.y_2);
if(clip_line(WC,LC_4))
Line(LC_4.x_1,LC_4.y_1,LC_4.x_2,LC_4.y_2);
if(clip_line(WC,LC_5))
Line(LC_5.x_1,LC_5.y_1,LC_5.x_2,LC_5.y_2);
if(clip_line(WC,LC_6))
Line(LC_6.x_1,LC_6.y_1,LC_6.x_2,LC_6.y_2);
getch( );
return 0;
}
//————————— clip_line( ) —————————-//
const int clip_line(const WindowCoordinates wc,LineCoordinates &lc){
float u_1=0;
float u_2=1;
float dx=(lc.x_2-lc.x_1);
float dy=(lc.y_2-lc.y_1);
float p1=(-dx);
float p2=dx;
float p3=(-dy);
float p4=dy;
float q1=(lc.x_1-wc.x_min);
float q2=(wc.x_max-lc.x_1);
float q3=(lc.y_1-wc.y_min);
float q4=(wc.y_max-lc.y_1);
if(check_line(p1,q1,u_1,u_2) && check_line(p2,q2,u_1,u_2) &&
check_line(p3,q3,u_1,u_2) && check_line(p4,q4,u_1,u_2))
{
if(u_2<1){
lc.x_2=(lc.x_1+(u_2*dx));
lc.y_2=(lc.y_1+(u_2*dy));}
if(u_1>0){
lc.x_1+=(u_1*dx);
lc.y_1+=(u_1*dy);}
lc.x_1=(int)(lc.x_1+0.5);
lc.y_1=(int)(lc.y_1+0.5);
lc.x_2=(int)(lc.x_2+0.5);
lc.y_2=(int)(lc.y_2+0.5);
return 1; }
return 0;}
//—————————— check_line( ) ————————/
const int check_line(const float p,const float q,float &u_1,float &u_2){
int flag=1;
float r=(q/p);
if(p<0) {
if(r>u_2)
flag=0;
else if(r>u_1)
u_1=r; }
else if(p>0) {
if(r<u_1)
flag=0;
else if(r<u_2)
u_2=r; }
else {
if(q<0)
flag=0; }
return flag;
}
//————————— Rectangle( ) —————————-//
void Rectangle(const int x_1,const int y_1,const int x_2,const int y_2) {
Line(x_1,y_1,x_2,y_1);
Line(x_2,y_1,x_2,y_2);
Line(x_2,y_2,x_1,y_2);
Line(x_1,y_2,x_1,y_1);
}
//————————– Line( ) ————————//
void Line(const int x_1,const int y_1,const int x_2,const int y_2){
int color=getcolor( );
int x1=x_1;
int y1=y_1;
int x2=x_2;
int y2=y_2;
if(x_1>x_2) {
x1=x_2;
y1=y_2;
x2=x_1;
y2=y_1; }
int dx=abs(x2-x1);
int dy=abs(y2-y1);
int inc_dec=((y2>=y1)?1:-1);
if(dx>dy) {
int two_dy=(2*dy);
int two_dy_dx=(2*(dy-dx));
int p=((2*dy)-dx);
int x=x1;
int y=y1;
putpixel(x,y,color);
while(x<x2){
x++;
if(p<0)
p+=two_dy;
else{
y+=inc_dec;
p+=two_dy_dx; }
putpixel(x,y,color);} }
else {
int two_dx=(2*dx);
int two_dx_dy=(2*(dx-dy));
int p=((2*dx)-dy);
int x=x1;
int y=y1;
putpixel(x,y,color);
while(y!=y2){
y+=inc_dec;
if(p<0)
p+=two_dx;
else{
x++;
p+=two_dx_dy;}
putpixel(x,y,color);
} } }