How to detect a full black color image in OpenCV Python?

Question

I want to write code in python to print a text when the input image is perfectly black and no other colors are present in it. Which are the functions to be used?

Answer 1

Try this:

# open the file with opencv
image = cv2.imread("image.jpg", 0)
if cv2.countNonZero(image) == 0:
    print "Image is black"
else:
    print "Colored image"

You basically check if all pixel values are 0 (black).