img = cv2.imread('test.png', 0)
contours, hierarchy = cv2.findContours(img, cv2.RETR_CCOMP, cv2.CHAIN_APPROX_TC89_L1)
area = []
topk_contours =[]
for i in range(len(contours)):
    a = cv2.contourArea(contours[i], True)
    area.append(abs(a))
topk = 2 #取最大面積的個(gè)數(shù)
for i in range(2):
    top = area.index(max(area))
    area.pop(top)
    topk_contours.append(contours[top])
x, y = img.shape
mask = np.zeros((x, y, 3))
mask_img = cv2.drawContours(mask, topk_contours, -1, (255, 255, 255), 1)
cv2.imwrite('mask_img.png', mask_img, [int(cv2.IMWRITE_JPEG_QUALITY), 100])
cv2.imshow('mask_img:', mask_img)
cv2.waitKey(0)
cv2.destroyAllWindows()

img = cv2.imread('test.png', 0)
contours, hierarchy = cv2.findContours(img, cv2.RETR_CCOMP, cv2.CHAIN_APPROX_TC89_L1)
area = []
topk_contours =[]
x, y = img.shape
for i in range(len(contours)):
    # 對(duì)每一個(gè)連通域使用一個(gè)掩碼模板計(jì)算非0像素(即連通域像素個(gè)數(shù))
    single_masks = np.zeros((x, y)) 
    fill_image = cv2.fillConvexPoly(single_masks, contours[i], 255)
    pixels = cv2.countNonZero(fill_image)
    area.append(pixels)
topk = 2 #取最大面積的個(gè)數(shù)
for i in range(2):
    top = area.index(max(area))
    area.pop(top)
    topk_contours.append(contours[top])
mask = np.zeros((x,y,3))
mask_img = cv2.drawContours(mask, topk_contours, -1, (255, 255, 255), 1)
cv2.imwrite('mask_img.png', mask_img, [int(cv2.IMWRITE_JPEG_QUALITY), 100])
cv2.imshow('mask_img:', mask_img)
cv2.waitKey(0)
cv2.destroyAllWindows()