# Flood fill algorithm using C graphics

## Concept

With respect of a given rectangle, our task is to fill this rectangle applying flood fill algorithm.

Input

rectangle(left = 50, top = 50, right= 100, bottom = 100)
floodFill( a = 55, b = 55, NewColor = 12, OldColor = 0)

Output

## Method

// A recursive function to replace previous color 'OldColor' at '(a, b)' and all surrounding pixels of (a, b) with new color 'NewColor' and floodFill(a, b, NewColor, OldColor)

• If a or b is outside the screen, thenreturn.

• If color of getpixel(a, b) is same asOldColor, then

• Recur for top, bottom, right and left.

floodFill(a+1, b, NewColor, OldColor);<

floodFill(a-1, b, NewColor, OldColor);

floodFill(a, b+1, NewColor, OldColor);

floodFill(a, b-1, NewColor, OldColor);

## Example

// Shows program to fill polygon using floodfill
// algorithm
#include <graphics.h>
#include <stdio.h>
// Describes flood fill algorithm
void flood(int x1, int y1, int new_col, int old_col){
// Checking current pixel is old_color or not
if (getpixel(x1, y1) == old_col) {
// Putting new pixel with new color
putpixel(x1, y1, new_col);
// Shows recursive call for bottom pixel fill
flood(x1 + 1, y1, new_col, old_col);
//Shows recursive call for top pixel fill
flood(x1 - 1, y1, new_col, old_col);
// Shows recursive call for right pixel fill
flood(x1, y1 + 1, new_col, old_col);
// Shows recursive call for left pixel fill
flood(x1, y1 - 1, new_col, old_col);
}
}
int main(){
int gd1, gm1 = DETECT;
// Initializing graph
initgraph(&gd1, &gm1, "");
//Shows rectangle coordinate
int top1, left1, bottom1, right1;
top1 = left1 = 50;
bottom1 = right1 = 300;
// Shows rectangle for print rectangle
rectangle(left1, top1, right1, bottom1);
// Fills start cordinate
int x1 = 51;
int y1 = 51;
// Shows new color to fill
int newcolor = 12;
// Shows old color which you want to replace
int oldcolor = 0;
// Calling for fill rectangle
flood(x1, y1, newcolor, oldcolor);
getch();
return 0;
}