Edit: original title "convert numpy array to cvmat" was a mistake - OpenCV's less than useful error message and my not reading the docs!
cvimage = cv2.imread("image.png") #using OpenCV 2 type(cvimage) Out: numpy.ndarray #dtype is uint8 pltimage = plt.imread("image.png") #using Matplotlib type(pltimage) Out: numpy.ndarray #dtype is float plt.imshow(cvimage) # works great cv2.imshow(cvimage) TypeError: Required argument 'mat' (pos 2) not found
cv2 uses NumPy arrays by default, there is no longer any cv::Mat constructor and NumPy has no functions to convert to a
The function has the following docstring:
imshow(winname, mat) -> None.
You can see the doc string by typing
cv2.imshow.__doc__ in the interpreter.
tl;dr : In original question, first argument of "window name" was missing. "imshow" takes two parameters and only one was supplied.
The question technically asks how to convert a NumPy Array (analogous to CV2 array) into a Mat object (CV). For anyone who is interested, this can be done by:
mat_array = cv.fromarray(numpy_array)
where mat_array is a Mat object, and numpy_array is a NumPy array or image. I would suggest staying away from older CV structures where possible. Numpy arrays offer much better performance than implemenations in native Python