How to get a region chain code?

[Valeriy Sokolov]

On Tue, Jul 16, 2013 at 9:03 AM, Chintak Sheth <chintaksheth at gmail.com>wrote:

> Hi Valeriy,
>
> Wow a compression technique! That would surely be a great addition.
>

Compression is cool no doubt, but I need it to turn the labeled shape into
a polygon =)


> > I am studying a shape descriptors and would like to compute a chain code
> description of a labeled shape. I was trying to look into docs but have not
> find a direct way to get this region property with skimage. Is there any
> way to do it in a few calls which I missed?
> >
>
> - Extract the boundary. `skimage.morphology.erosion` using
> `skimage.morphology.disk` structuring element with radius 1. Then subtract
> this from the original image.
>
I suppose `skimage.morphology.dilation` would work better. It will work in
case we computing chain code for the line of 1-pixel width.

> - Label the boundaries. If you already have a labeled image, then that
> saves you a function call else there is `label` function in
> `skimage.morphology`.
>
> - Use `np.transpose(np.where(label == 1))` to generate the indices of
> pixels marked as label 1. This will return a `list` of indices. You can
> simply use the first as the starting point.
>
> This should help set up the stage for the traversal. Hope this helps a bit.
>
The traverse is the most interesting part in this question =) The other
things do not introduce order on the pixels and could be made with current
skimage easily.


> Chintak.
>
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-- 
Best regards,
Valeriy Sokolov.
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