I'm getting an error error: C:\builds\master_PackSlaveAddon-win32-vc12-static\opencv\modules\core\src\stat.cpp:1297: error: (-215) cn == 1 in function cv::countNonZero

Hi, This is my first post in this forum. I've written a color detection program for detecting Magenta color(only). But now I want to print a text when the magenta color is not present.Which means I want to detect a perfect black image for that.How can I do that?

import cv2 import numpy as np cap = cv2.VideoCapture(0) while(1):

Take each frame

_, frame = cap.read()

# Convert BGR to HSV
hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

# define range of blue color in HSV
lower_blue = np.array([140,100, 140], dtype=np.uint8)
upper_blue = np.array([150,255,255], dtype=np.uint8)

# Threshold the HSV image to get only blue colors
mask = cv2.inRange(hsv, lower_blue, upper_blue)

# Bitwise-AND mask and original image
res = cv2.bitwise_and(frame,frame, mask= mask)

cv2.imshow('frame',frame)
cv2.imshow('mask',mask)
cv2.imshow('res',res)
k = cv2.waitKey(5) & 0xFF
if k == 27:
    break

cv2.destroyAllWindows()