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From: Brendan <brendandetracey@yahoo.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: outer perimeter binary blobs - vectorisation
Date: Tue, 8 Sep 2009 17:04:07 -0700 (PDT)
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On Sep 8, 11:03 am, ImageAnalyst <imageanal...@mailinator.com> wrote:
> Brendan:
> Your algorithm gets the enclosing perimeter - pixels that are outside
> the blob, not part of the blob.  You can erode the entire image (no
> need to loop over individual blobs), and then subtract that from the
> original image to get the perimeters.  This way the perimeters will
> actually be a part of your blob - the outermost layer of pixels that
> are still contained within your blob.  You can race that algorithm
> against the built-in bwboundaries() to see which is faster.
> Good luck,
> ImageAnalyst

Thanks for the answer.

I am trying replicate a cloud masking paper in which edge pixels are
determined by thresholding cluster shade. The paper then compares the
mean pixel value for each edge against the mean pixel value for each
interior. My starting point is a bitmap of unsorted edge pixels. I
think I am stuck with looping unless I use the inner perimeter,
however this will disqualify small blobs.