src_depth != CV_32S in function 'convertToShow'

Traceback (most recent call last):
  File "D:/Python/測試專用文件夾/opencv測試.py", line 17, in <module>
    cv2.imshow('saf', img)
cv2.error: OpenCV(4.1.0) C:/projects/opencv-python/opencv/modules/highgui/src/precomp.hpp:131: error: (-215:Assertion failed) src_depth != CV_16F && src_depth != CV_32S in function 'convertToShow'

錯誤代碼

import cv2
import numpy as np
from scipy import ndimage
import time

l=10
a=[]
for i in range(10):
    a.append([250, 10, 50])
b=[]
for i in range(10):
    b.append(a)
print(b)

img = np.array(b)

img *= 250

cv2.imshow('saf', img)
cv2.waitKey(0)

報錯內容

cv2.error: OpenCV(4.1.0) C:/projects/opencv-python/opencv/modules/highgui/src/precomp.hpp:131: error: (-215:Assertion failed) src_depth != CV_16F && src_depth != CV_32S in function 'convertToShow'

錯誤緣由

次像素的數據格式有要求，能夠指定dtype=np.uint8或者dtype=np.float32

完整代碼

import cv2
import numpy as np


l = 10
a = []
for i in range(500):
    a.append([120, 10, 50])
b = []
for i in range(500):
    b.append(a)
print(b)

img = np.array(b, dtype=np.uint8)

cv2.imshow('saf', img)
cv2.waitKey(0)