skimage's rgb2gray in python: AttributeError: Nonetype object has no attribute ndim
Question: I was using this code (with skimage version 0.10.0) as far as I can remember
without issues:

    
    
    from scipy import misc
    import scipy.io as sio
    from skimage.color import rgb2gray
    
    img = cv2.imread(myfile)
    img = rgb2gray(img)
    

But now I'm getting this error:

    
    
    Traceback (most recent call last):
      File "C:\work_asaaki\code\generateProposals.py", line 48, in <module>
        img = rgb2gray(img)
      File "C:\Anaconda\lib\site-packages\skimage\color\colorconv.py", line 635, in rgb2gray
        if rgb.ndim == 2:
    AttributeError: 'NoneType' object has no attribute 'ndim'
    

What could the problem possibly be? How can I fix it to be able to convert the
image to grayscale?


Answer: Given the error message your problem is that the `imread` call fails, which
means `img`is `None`.

Reason for why the `imread` call fails is usually that the path to the file is
wrong.

