opencv ： ValueError: too many values to unpack (expected 2)

基於opencv-python 執行 cv2.findContours()函數出現以下錯誤提示：

Traceback (most recent call last):

contours, hierarchy = cv2.findContours(gray_temp, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
ValueError: too many values to unpack (expected 2)

代碼如下：

# find connected domain in image
def findContours(image):
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    gray_temp = gray.copy()
    contours, hierarchy = cv2.findContours(gray_temp, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
    contoursSize = np.size(contours)
    return contours, hierarchy, contoursSize
    #print("contoursSize is ", contoursSize)

原因： 

基於opncv4.1.0的  findContours 是可以接受兩個返回值的

但是基於opencv3.4.15的 findContours是需要接受三個返回值的

修改爲：binary, contours, hierarchy = cv2.findContours(gray_temp, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)