Connected-component-labeling | First step | Data Labeling library

image = cv2.imread('image.png', cv2.IMREAD_UNCHANGED);
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
binary = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY | cv2.THRESH_OTSU)[1]

# getting mask with connectComponents
ret, labels = cv2.connectedComponents(binary)
for label in range(1,ret):
    mask = np.array(labels, dtype=np.uint8)
    mask[labels == label] = 255
    cv2.imshow('component',mask)
    cv2.waitKey(0)

# getting ROIs with findContours
contours = cv2.findContours(binary, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)[1]
for cnt in contours:
    (x,y,w,h) = cv2.boundingRect(cnt)
    ROI = image[y:y+h,x:x+w]
    cv2.imshow('ROI', ROI)
    cv2.waitKey(0)

cv2.destroyAllWindows()