OpenCV TypeError: Expected cv::UMat for argument 'src' - What is this?

问题

Disclaimer: huge openCV noob

Traceback (most recent call last):

File "lanes2.py", line 22, in
canny = canny(lane_image)
File "lanes2.py", line 5, in canny
gray = cv2.cvtColor(imgUMat, cv2.COLOR_RGB2GRAY)
TypeError: Expected cv::UMat for argument 'src'

What exactly is 'src' referring to?

回答1:

src is the first argument to cv2.cvtColor.

The error you are getting is because it is not the right form. cv2.Umat() is functionally equivalent to np.float32(), so your last line of code should read:

gray = (np.float32(imgUMat), cv2.COLOR_RGB2GRAY)

回答2:

gray = cv2.cvtColor(cv2.UMat(imgUMat), cv2.COLOR_RGB2GRAY)

UMat is a part of the Transparent API (TAPI) than help to write one code for the CPU and OpenCL implementations.

回答3:

Not your code is the problem this is perfectly fine:

gray = cv2.cvtColor(imgUMat, cv2.COLOR_RGB2GRAY)

The problem is that imgUMat is None so you probably made a mistake when loading your image:

imgUMat = cv2.imread("your_image.jpg")

I suspect you just entered the wrong image path.

回答4:

The following can be used from numpy:

import numpy as np 
image = np.array(image)

回答5:

Is canny your own function? Do you use Canny from OpenCV inside it? If yes check if you feed suitable argument for Canny - first Canny argument should meet following criteria:

type: <type 'numpy.ndarray'>
dtype: dtype('uint8')
being single channel or simplyfing: grayscale, that is 2D array, i.e. its shape should be 2-tuple of ints (tuple containing exactly 2 integers)

You can check it by printing respectively

type(variable_name)
variable_name.dtype
variable_name.shape

Replace variable_name with name of variable you feed as first argument to Canny.

回答6:

This is a general error, which throws sometimes, when you have mismatch between the types of the data you use. E.g I tried to resize the image with opencv, it gave the same error. Here is a discussion about it.

回答7:

Sometimes I have this error when videostream from imutils package doesn't recognize frame or give an empty frame. In that case, solution will be figuring out why you have such a bad frame or use a standard VideoCapture(0) method from opencv2

回答8:

Just add this at start: image = cv2.imread(image)

来源：https://stackoverflow.com/questions/54249728/opencv-typeerror-expected-cvumat-for-argument-src-what-is-this

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typeerror

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