Task: Bitmap_Flood fill
C: 
#define _CRT_SECURE_NO_WARNINGS 
#include <stdio.h>
#include <stdlib.h>

#define MAXSIZE 2048
#define BYTE unsigned char

static int width, height;
static BYTE bitmap[MAXSIZE][MAXSIZE];
static BYTE oldColor;
static BYTE newColor;

void floodFill(int i, int j)
{   
    if ( 0 <= i && i < height 
    &&   0 <= j && j < width 
    &&   bitmap[i][j] == oldColor )
    {
        bitmap[i][j] = newColor;
        floodFill(i-1,j);
        floodFill(i+1,j);
        floodFill(i,j-1);
        floodFill(i,j+1);
    }
}



void skipLine(FILE* file)
{
    while(!ferror(file) && !feof(file) && fgetc(file) != '\n')
        ;
}

void skipCommentLines(FILE* file)
{
    int c;
    int comment = '#';

    while ((c = fgetc(file)) == comment) 
        skipLine(file);
    ungetc(c,file);
}

readPortableBitMap(FILE* file)
{
    int i,j;

    skipLine(file);
    skipCommentLines(file);  fscanf(file,"%d",&width);
    skipCommentLines(file);  fscanf(file,"%d",&height);
    skipCommentLines(file);

    if ( width <= MAXSIZE && height <= MAXSIZE )
        for ( i = 0; i < height; i++ )
            for ( j = 0; j < width; j++ )
                fscanf(file,"%1d",&(bitmap[i][j]));
    else exit(EXIT_FAILURE);
}

void writePortableBitMap(FILE* file)
{
    int i,j;
    fprintf(file,"P1\n");
    fprintf(file,"%d %d\n", width, height);
    for ( i = 0; i < height; i++ )
    {
        for ( j = 0; j < width; j++ )
            fprintf(file,"%1d", bitmap[i][j]);
        fprintf(file,"\n");
    }
}



int main(void)
{
    oldColor = 1;
    newColor = oldColor ? 0 : 1;
    readPortableBitMap(stdin);
    floodFill(height/2,width/2);
    writePortableBitMap(stdout);
    return EXIT_SUCCESS;
}

Python: from collections import deque

image_file = "image.png"
fill_color = color(250, 0, 0)
tolerance = 15
allowed = False

def setup():
    global img
    size(600, 400)
    img = loadImage(image_file)
    fill(0, 0, 100)
    textSize(18)
    show()
    
def show():
    image(img, 0, 0, width, height)
    text("Tolerance = {}    (Use mouse wheel to change)".format(tolerance),
         100, height - 30)
    text("Right click to reset", 100, height - 10)
 
def draw():
    global allowed
    if allowed:
        show()
        allowed = False

def mousePressed():
    global allowed, img
    if mouseButton == RIGHT:
        img = loadImage(image_file)
    else:
        img.loadPixels()
        flood(mouseX, mouseY)
        img.updatePixels()
    allowed = True    

def mouseWheel(event):
    global allowed, tolerance
    e = event.getCount()
    tolerance += 2 * e
    if tolerance > 128:
        tolerance = 128
    if tolerance < 0:
        tolerance = 0
    allowed = True

def flood(x, y):
    target_color = img.pixels[pixel_position(mouseX, mouseY)]
    if target_color != fill_color:
        queue = deque()
        queue.append((x, y))
        while len(queue) > 0:
            p_x, p_y = queue.popleft()
            if (check(p_x, p_y, target_color)):
                queue.append((p_x, p_y - 1))
                queue.append((p_x, p_y + 1))
                queue.append((p_x - 1, p_y))
                queue.append((p_x + 1, p_y))

def pixel_position(x, y):
    return x + (y * img.width)

def check(x, y, target_color):
    if x < 0 or y < 0 or y >= img.height or x >= img.width:
        return False
    pp = img.pixels[pixel_position(x, y)]
    test_tolerance = (abs(green(target_color) - green(pp)) < tolerance
                      and abs(red(target_color) - red(pp)) < tolerance
                      and abs(blue(target_color) - blue(pp)) < tolerance)
    if not test_tolerance:
        return False
    img.pixels[pixel_position(x, y)] = fill_color
    return True