OpenCV floodfill with mask

Question

The documentation for OpenCV\'s floodfill function states:

The function uses and updates the mask, so you take responsibility of initializing the ma

Answer 1

And a python version

im = cv2.imread("seagull.jpg")
h,w,chn = im.shape
seed = (w/2,h/2)

mask = np.zeros((h+2,w+2),np.uint8)

floodflags = 4
floodflags |= cv2.FLOODFILL_MASK_ONLY
floodflags |= (255 << 8)

num,im,mask,rect = cv2.floodFill(im, mask, seed, (255,0,0), (10,)*3, (10,)*3, floodflags)

cv2.imwrite("seagull_flood.png", mask)

(Seagull image from Wikimedia: https://commons.wikimedia.org/wiki/Commons:Quality_images#/media/File:Gull_portrait_ca_usa.jpg)

Result: