A C++ program to fill polygon using Boundary fill algorithm


#include<graphics.h>
#include<iostream>
#include<conio.h>
#include<math.h>
using namespace std;
void line1(const int,const int,const int,const int);
void polygon1(const int,const int []);
void boundry_fill2(const int , const int, const int , const int);
int main(){
int gd=DETECT,gm;
initgraph(&gd,&gm,” “);
int polygon_points[14]={365,325, 400,290, 450,290, 485,325, 450,360,
400,360, 365,325};
setcolor(15);
polygon1(7,polygon_points);
boundry_fill2(425,325,14,15);
setcolor(15);
settextstyle(0,0,1);
outtextxy(395,370,”polygon”);
getch();
return 0;}
//boundryfill
void boundry_fill2(const int x, const int y, const int fill_color, const int border_color){
int interior_color;
interior_color=getpixel(x,y);
if((interior_color!=border_color) && (interior_color!=fill_color)){
putpixel(x,y,fill_color);
boundry_fill2(x+1,y,fill_color,border_color);
boundry_fill2(x-1,y,fill_color,border_color);
boundry_fill2(x,y-1,fill_color,border_color);
boundry_fill2(x,y+1,fill_color,border_color);
} }
//polygon//
void polygon1(const int n,const int coordinates[]){
if(n>=2){
line1(coordinates[0],coordinates[1],coordinates[2],coordinates[3]);
for(int count=1;count<(n-1);count++)
line1(coordinates[(count*2)],coordinates[((count*2)+1)],coordinates[((count
+1)*2)],coordinates[(((count+1)*2)+1)]); } }
//line
void line1(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);
}}}