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Editorial Team
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Asked: 2026-05-29T12:30:11+00:00

I am trying to use the Python opencv function Moments() on a grayscale image,

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I am trying to use the Python opencv function Moments() on a grayscale image, but I receive the following TypeError:

>>> img = cv.LoadImage('example_image.jpg', cv.CV_LOAD_IMAGE_GRAYSCALE)
>>> moments = cv.Moments(img)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Argument '' must be CvSeq, CvArr, or a sequence of numbers
>>>

I am confident this usage is correct as it is demonstrated in the opencv docs here, where GetHuMoments() uses the results from Moments().

I believe I have opencv and numpy installed correctly, as I have been successfully using them for many other things, and I encounter this on both OS X 10.6 and Red Hat 6.

The same question is posed in the opencv user group, but I don’t want to convert the image to a contour first as the reply instructs.

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1 Answer

  1. Editorial Team

    Looks like you need to force conversion from IplImage to cvMat

    There was a previous question “Capture Image as Array with Python OpenCV”

    Capture Image as Array with Python OpenCV

    e.g for me

    >>> mm=cv.Moments(img)
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: Argument '' must be CvSeq, CvArr, or a sequence of numbers
>>> mat=cv.GetMat(img)
>>> mm=cv.Moments(mat)
>>> mm.m00
181428.0
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