[SciPy-User] ndimage/morphology - binary dilation and erosion?

klo uo klonuo@gmail....
Sat Mar 31 12:09:41 CDT 2012


On Sat, Mar 31, 2012 at 6:48 PM, Tony Yu <tsyu80@gmail.com> wrote:

>
>> 1. Is this result correct? From what I read today seems like what
>> dilation does is erosion and vice versa, but I probably overlooked something
>>
>
> This result looks correct to me. I think it depends on what you consider
> "object" and "background": Typically (I think), image-processing operators
> consider light regions to be objects and dark objects to be background. So
> dilation grows right regions and erosion shrinks bright regions. Obviously,
> in your images, definitions of object and background are reversed (black is
> object; white is background).
>

You are right. I thought on first it couldn't be flip logic, but thinking
more about it and then backing with result from abs(img-1) shows it's just
like that.



> 2. Does someone maybe know of better approach for enhancing original
>> sample for OCR (except thresholding, for which I'm aware)?
>>
>
> Have you tried the `open` and `close` operators? A morphological opening
> is just an erosion followed by a dilation and the closing is just the
> reverse (see e.g., the scikits-image docstrings<http://scikits-image.org/docs/dev/api/skimage.morphology.html#greyscale-open>).
> For an opening, the erosion would remove some of "salt" (white pixels) in
> the letters, and the dilation would (more-or-less) restore the letters to
> their original thickness. The closing would do the same for black pixels on
> the background.
>

Thanks for suggestion. Is morphology module in skimage reflection of
ndimage, or it's separate implementation?
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