Using cv2.imread: “<built-in function imread> returned NULL without setting an error”, as if it can't open the picture or get the data

问题

This is the part of my code that gives the problem. It is supposed to count the amount of green pixels in a picture:

img = Image.open('path.tif')

BLACK_MIN = np.array([0, 20, 20], np.uint8)

BLACK_MAX = np.array([120, 255, 255], np.uint8)

imgg = cv2.imread(img, 1)

dst = cv2.inRange(imgg, BLACK_MIN, BLACK_MAX)

no_black = cv2.countNonZero(dst)

print('The number of black pixels is: ' + str(no_black))

回答1:

You are passing a PIL image to imread but it expects a filepath (https://docs.opencv.org/2.4/modules/highgui/doc/reading_and_writing_images_and_video.html?highlight=imread#Mat%20imread(const%20string&%20filename,%20int%20flags)

You should use:

imgg = cv2.imread('path.tif', 1)

回答2:

Image is already readed using PIL.Now the img is in array format so you cannot able to read it again.Read your file in any one kind of format either pil or cv2

BLACK_MIN = np.array([0, 20, 20], np.uint8)

BLACK_MAX = np.array([120, 255, 255], np.uint8)

imgg = cv2.imread('path.tif', 1)

dst = cv2.inRange(imgg, BLACK_MIN, BLACK_MAX)

no_black = cv2.countNonZero(dst)

print('The number of black pixels is: ' + str(no_black))

来源：https://stackoverflow.com/questions/58123915/using-cv2-imread-built-in-function-imread-returned-null-without-setting-an-e