Flood fill algorithm in c++

Flood Fill Algorithm-

Flood fill algorithm is used to color the polygon.This comes under seed fill algorithm.To color a polygon we use either 4-connected method or 8-connected method.

 

4-connected method-

In this method, we choose a seed pixel and color it with new color after this we color the neighbourhood pixels and so on.

8-connected method-

In this method, we choose a seed pixel and color it with new color after this we color all eight neighbourhood pixels and so on.

we can see this by this picture-

Source-https://www.cs.auckland.ac.nz/courses/compsci773s1c/lectures/ImageProcessing-html/neighbourhoods.gif

Here is the c++ program for flood fill algorithm-

#include<bits/stdc++.h>
#include<graphics.h>
using namespace std;
//function to implement floodfill algorithm
void floodfill(int x,int y,int old,int newcol)
{
 //getpixel() gives the color of pixel (x,y)
 int curr=getpixel(x,y);
 //if the color of current pixel is same as the old color then color this to new color
 if(curr==old)
 {
  delay(10);
  //color the current pixel with new color
  putpixel(x,y,newcol);
  //repeat the process for 8 neighbouring pixels
  floodfill(x-1,y,old,newcol);
  floodfill(x+1,y,old,newcol);
  floodfill(x,y-1,old,newcol);
  floodfill(x,y+1,old,newcol);
  floodfill(x+1,y+1,old,newcol);
  floodfill(x-1,y+1,old,newcol);
  floodfill(x-1,y-1,old,newcol);
  floodfill(x+1,y-1,old,newcol);
 }
}
int main ()
{
 int gd,gm;
 detectgraph(&gd,&gm);
 initgraph(&gd,&gm," ");
 //function to draw rectangle
 rectangle(100,100,200,200);
 //call the function with the points that exist inside the polygon we are going to color
 floodfill(110,110,0,2);
 getch();
return 0;
}

OUTPUT-

To execute this program-

• Save the above-given code with .cpp extension i.e.(file.cpp).
•  open the terminal and write the command         

  g++ file.cpp -lgraph

• After this execute ./a.out file and you will see the output shown below-