ValueError: Image is not numeric, but ndarray

Question

I'm trying to save a sci-kit image, but I'm getting the error:

ValueError: Image is not numeric, but ndarray.

Code:

from skimage import *
import skimage.io
import skimage.morphology as morphology

def loadImage(f):
    return skimage.img_as_float(skimage.io.imread(f))

img = img_as_bool(loadImage("images/metric_map_processed.PNG"))

imgSk = morphology.medial_axis(img)
skimage.io.imsave("medial.png", imgSk)

According to the docs, the passed in array should be a ndarray, so why am I getting an error?

Could you put that error against the code where you are getting the error? We can't see line numbers here. — Divakar
– Divakar, Commented Aug 2, 2019 at 6:39
@Divakar Hi, just realised the issue was due to the image being converted to binary. — Alex
– Alex, Commented Aug 2, 2019 at 6:45

Alex · Accepted Answer · 2019-08-02 06:40:43Z

3

Just realised that my image was being converted to binary

Replacing

skimage.io.imsave("medial.png", imgSk)

with

skimage.io.imsave("medial.png", img_as_uint(imgSk))

worked for me

answered Aug 2, 2019 at 6:40

Alex

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Comments

Grzegorz Bokota · Accepted Answer · 2019-08-02 06:59:52Z

1

The problem is that pixel type in png is uint8. And when you apply img_as_bool you get boolean array. And this mismatch of type generate error.

You need to convert it to uint8. As suggest Alex use img_as_uint function.

answered Aug 2, 2019 at 6:59

Grzegorz Bokota

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