# C++ Graphics Program to Implement Mid-point Subdivision Line Clipping Algorithm

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## Program Code

``````# include <iostream>
# include <graphics.h>
# include <conio.h>
# include <math.h>
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; } };
//—————————– RegionCode —————————-//
class RegionCode {
public:
int bit_1;
int bit_2;
int bit_3;
int bit_4;
RegionCode( ){
bit_1=0;
bit_2=0;
bit_3=0;
bit_4=0; }
const int equal_zero( ) {
if(bit_1==0 && bit_2==0 && bit_3==0 && bit_4==0)
return 1;
return 0;}
void get_logical_AND(RegionCode rc1,RegionCode rc2){
if(rc1.bit_1==1 && rc2.bit_1==1)
bit_1=1;
if(rc1.bit_2==1 && rc2.bit_2==1)
bit_2=1;
if(rc1.bit_3==1 && rc2.bit_3==1)
bit_3=1;
if(rc1.bit_4==1 && rc2.bit_4==1)
bit_4=1;}
void get_region_code(const WindowCoordinates wc,const int x,const int y)
{
if((wc.x_min-x)>0)
bit_1=1;
if((x-wc.x_max)>0)
bit_2=1;
if((wc.y_min-y)>0)
bit_3=1;
if((y-wc.y_max)>0)
bit_4=1;
} };
const int clip_line(const WindowCoordinates,LineCoordinates&);
void calculate_intersecting_points(const WindowCoordinates,LineCoordinates&);
void Rectangle(const int,const int,const int,const int);
void Line(const int,const int,const int,const int);
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; }
const int clip_line(const WindowCoordinates wc,LineCoordinates &lc){
RegionCode rc1,rc2,rc;
rc1.get_region_code(wc,lc.x_1,lc.y_1);
rc2.get_region_code(wc,lc.x_2,lc.y_2);
rc.get_logical_AND(rc1,rc2);
if(rc1.equal_zero( ) && rc2.equal_zero( ))
return 1;
else if(!rc.equal_zero( ))
return 0;
else {
calculate_intersecting_points(wc,lc);
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);
if(lc.x_1==lc.x_2 && lc.y_1==lc.y_2)
return 0; }
return 1;}
void calculate_intersecting_points(const WindowCoordinates wc,LineCoordinates
&lc){
LineCoordinates lc1(lc.x_1,lc.y_1,lc.x_2,lc.y_2);
LineCoordinates lc2(lc.x_2,lc.y_2,lc.x_1,lc.y_1);
float x_mid;
float y_mid;
if(lc1.y_1>wc.y_max) {
while(lc1.y_1!=wc.y_max){
x_mid=((lc1.x_1+lc1.x_2)/2);
y_mid=((lc1.y_1+lc1.y_2)/2);
if(y_mid>=wc.y_max){
lc1.x_1=x_mid;
lc1.y_1=y_mid; }
else{
lc1.x_2=x_mid;
lc1.y_2=y_mid; }
if((int)(lc1.x_1+0.5)==(int)(lc1.x_2+0.5) &&
(int)(lc1.y_1+0.5)==(int)(lc1.y_2+0.5))
break;} }
else if(lc1.y_1<wc.y_min) {
while(lc1.y_1!=wc.y_min){
x_mid=((lc1.x_1+lc1.x_2)/2);
y_mid=((lc1.y_1+lc1.y_2)/2);
if(y_mid<=wc.y_min){
lc1.x_1=x_mid;
lc1.y_1=y_mid;}
else{
lc1.x_2=x_mid;
lc1.y_2=y_mid;}
if((int)(lc1.x_1+0.5)==(int)(lc1.x_2+0.5) &&
(int)(lc1.y_1+0.5)==(int)(lc1.y_2+0.5))
break;
} }
if(lc1.x_1>wc.x_max) {
while(lc1.x_1!=wc.x_max){
x_mid=((lc1.x_1+lc1.x_2)/2);
y_mid=((lc1.y_1+lc1.y_2)/2);
if(x_mid>=wc.x_max){
lc1.x_1=x_mid;
lc1.y_1=y_mid; }
else{
lc1.x_2=x_mid;
lc1.y_2=y_mid;}
if((int)(lc1.x_1+0.5)==(int)(lc1.x_2+0.5) &&
(int)(lc1.y_1+0.5)==(int)(lc1.y_2+0.5))
break;} }
else if(lc1.x_1<wc.x_min) {
while(lc1.x_1!=wc.x_min){
x_mid=((lc1.x_1+lc1.x_2)/2);
y_mid=((lc1.y_1+lc1.y_2)/2);
if(x_mid<=wc.x_min){
lc1.x_1=x_mid;
lc1.y_1=y_mid;}
else {
lc1.x_2=x_mid;
lc1.y_2=y_mid;}
if((int)(lc1.x_1+0.5)==(int)(lc1.x_2+0.5) &&
(int)(lc1.y_1+0.5)==(int)(lc1.y_2+0.5))
break;
} }
lc2.x_2=lc1.x_1;
lc2.y_2=lc1.y_1;
if(lc2.y_1>wc.y_max) {
while(lc2.y_1!=wc.y_max){
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);
if(y_mid>=wc.y_max){
lc2.x_1=x_mid;
lc2.y_1=y_mid;}
else{
lc2.x_2=x_mid;
lc2.y_2=y_mid;}
if((int)(lc2.x_1+0.5)==(int)(lc2.x_2+0.5) &&
(int)(lc2.y_1+0.5)==(int)(lc2.y_2+0.5))
break;
} }
else if(lc2.y_1<wc.y_min) {
while(lc2.y_1!=wc.y_min){
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);
if(y_mid<=wc.y_min){
lc2.x_1=x_mid;
lc2.y_1=y_mid; }
else{
lc2.x_2=x_mid;
lc2.y_2=y_mid; }
if((int)(lc2.x_1+0.5)==(int)(lc2.x_2+0.5) &&
(int)(lc2.y_1+0.5)==(int)(lc2.y_2+0.5))
break;} }
if(lc2.x_1>wc.x_max) {
while(lc2.x_1!=wc.x_max){
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);
if(x_mid>=wc.x_max) {
lc2.x_1=x_mid;
lc2.y_1=y_mid; }
else{
lc2.x_2=x_mid;
lc2.y_2=y_mid; }
if((int)(lc2.x_1+0.5)==(int)(lc2.x_2+0.5) &&
(int)(lc2.y_1+0.5)==(int)(lc2.y_2+0.5))
break;
} }
else if(lc2.x_1<wc.x_min) {
while(lc2.x_1!=wc.x_min){
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);
if(x_mid<=wc.x_min){
lc2.x_1=x_mid;
lc2.y_1=y_mid;}
else{
lc2.x_2=x_mid;
lc2.y_2=y_mid;}
if((int)(lc2.x_1+0.5)==(int)(lc2.x_2+0.5) &&
(int)(lc2.y_1+0.5)==(int)(lc2.y_2+0.5))
break;
} }
lc.x_1=lc1.x_1;
lc.y_1=lc1.y_1;
lc.x_2=lc2.x_1;
lc.y_2=lc2.y_1; }
//————————— 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);
} } }``````

## Final Words

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