from PIL import Image

BORDER_WIDTH = 5
TARGET_COLOR = (255,0,0)

#using both of these as globals because I'm too lazy to pass them to every function
img = Image.open("sample.png")
pix = img.load()

def neighbor_coords(x,y):
    for dx,dy in ((0,1), (0,-1), (1,0), (-1,0)):
        if 0 <= x+dx < img.size[0] and 0 <= y+dy <= img.size[1]:
            yield x+dx, y+dy

def flood_fill(x,y):
    color = pix[x,y]
    seen = set()
    to_visit = {(x,y)}
    while to_visit:
        x,y = to_visit.pop()
        #print(len(to_visit), len(seen), x,y, pix[x,y])
        seen.add((x,y))
        for nx, ny in neighbor_coords(x,y):
            if pix[nx,ny] == color and (nx,ny) not in seen:
                to_visit.add((nx,ny))
    return seen

def get_features():
    features = []
    seen = set()
    for i in range(img.size[0]):
        for j in range(img.size[1]):
            if pix[i,j] == TARGET_COLOR and (i,j) not in seen:
                feature = flood_fill(i,j)
                seen.update(feature)
                features.append(feature)
    return features

def is_rectangle(feature):
    left = min(p[0] for p in feature)
    right = max(p[0] for p in feature)
    top = min(p[1] for p in feature)
    bottom = max(p[1] for p in feature)
    for delta in range(BORDER_WIDTH):
        for i in range(left+delta, right+1-delta):
            if (i, top+delta) not in feature: return False
            if (i, bottom-delta) not in feature: return False
        for j in range(top+delta, bottom+1-delta):
            if (left+delta, j) not in feature: return False
            if (right-delta, j) not in feature: return False
    return True

features = get_features()
print("Found {} feature(s).".format(len(features)))
rects = list(filter(is_rectangle, features))
print("Found {} rectangle(s).".format(len(rects)))