[scikit-image] GLCM for non-rectangular image

NASAHARA Kenlo 24dakenlo at gmail.com
Wed Sep 6 21:23:24 EDT 2017


Dear scikit-image community:

I am trying GLCM functions in scikit-image. 
http://scikit-image.org/docs/dev/auto_examples/features_detection/plot_glcm.html

I wonder whether they can treat images with irregular 
shapes, such as a circle, an oval, or some more complex 
forms (not only rectagle). 

In the "greycomatrix", function:

    def greycomatrix(image, distances, angles, levels=None, symmetric=False, normed=False):
    
    image : array_like
        Integer typed input image. Only positive valued images are supported.
        If type is other than uint8, the argument `levels` needs to be set.

the "image" seems to be required to be a rectangle. 

If NAN or NULL values are allowed in the "image", and the function skips 
treating those "no-data" pixels assigned with NAN or NULL, then we 
may be able to treat any shapes of image, by filling the pixels outside the
boudary with NAN or NULL.

However, in the source code of "_glcm_loop" function
(https://searchcode.com/codesearch/view/83509141/),  all the pixels 
within the rectangular image are scanned, without permitting "no-data".

My questions:
1. Do you know how to treat GLCM in non-rectangular image with
scikit-image?
2. If not, do you know any other ways to do that instead of scikit-image?
3. Do you think it is a reasonable idea to change GLCM functions in 
  scikit-image so that they can treat no-data (allowing NAN or NULL)?

-- 
Kenlo Nishida Nasahara
Faculty of Life and Environmental Sciences
University of Tsukuba, Japan 305-8572
24dakenlo at gmail.com


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