cv2.error: OpenCV(4.7.0) /io/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'

This error occurs when the input image to the cvtColor() function is empty or null. This means that the image you are trying to convert is not being properly loaded or is not being passed correctly to the function.

To resolve this issue, you can try the following steps:

1. Check the file path or image source to ensure that the image is being loaded correctly.
2. Make sure that the image is not empty or null before passing it to the cvtColor() function.
3. Try using a different image to see if the issue is specific to the current image.
4. Update your OpenCV version to the latest version to ensure that the issue is not related to a bug in an older version.

If none of these steps resolve the issue, you may need to provide more information about your code and the environment you are working in to receive more specific guidance.