how to get the number of channels from an image, in OpenCV 2?

Question

The answers at Can I determine the number of channels in cv::Mat Opencv answer this question for OpenCV 1: you use the Mat.channels() method of the image.

Answer 1

I'm kind of late but there is another simple way out there:

Use image.ndim Source, will give your right number of channels as below:

if image.ndim == 2:

    channels = 1 #single (grayscale)

if image.ndim == 3:

    channels = image.shape[-1]

Since a image is a nothing but a numpy array. Checkout OpenCV docs here: docs

Answer 2

As i know, u should use image.shape[2] to determine number of channels, not len(img.shape), the latter gives the dimensions of the array.

Answer 3

Use img.shape

It provides you the shape of img in all directions. ie number of rows, number of columns for a 2D array (grayscale image). For 3D array, it gives you number of channels also.

So if len(img.shape) gives you two, it has a single channel.

If len(img.shape) gives you three, third element gives you number of channels.

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