Better results with Canny/Hough for circular particles
Adam Hughes
hughesadam87 at gmail.com
Fri Dec 13 15:25:53 EST 2013
Hi Dan,
Thanks for the quick reply.
I think that I can get better results if I tweak the parameters. The
threshold parameter intuitively makes sense, but I'll have to read a bit to
get familiar with sigma and the algorithm in general. Thanks for the
explanation; it really helped. I will try out the erosion as well.
PS, do you have any feelings towards the applicability of circular hough to
my image?
On Friday, December 13, 2013 3:03:30 PM UTC-5, Dan Farmer wrote:
>
> Hi Adam,
>
> This can be the worst part of image processing, but I'm curious how
> much you played with the parameters to Canny? You probably know this,
> but canny already tries to close gaps (hysteresis thresholding). What
> you want to do is try to lower the low_threshold parameter (values
> above the high threshold value get initially labeled as edges, then it
> looks for pixels that are connected to edge pixels and whose value is
> > low_threshold to link the edges).
>
> An easy/basic way to get rid of small fragments would be to start with
> morphological erosion.
>
> -Dan
>
> On Fri, Dec 13, 2013 at 11:47 AM, Adam Hughes <hughes... at gmail.com<javascript:>>
> wrote:
> > Hi,
> >
> > I have several images of circular particles (see attached for an
> example)
> > and I've been experimenting with automatic routines to find edges.
> >
> > I've found that with Canny, I can get really nice edges, but the edges
> are
> > not always connected. Thus, when I do fill-binary, many of my particles
> are
> > not painted in due to slight breaks in the border returned by canny. Is
> > there an ideal way to fix this, either by connecting "almost" connected
> > canny edges? Additionally, what is the best way to filter out small
> > fragments and/or non-circular edges?
> >
> > I've attached an image of the canny outlines; you can see that I
> obviously
> > want to get rid some of the regions that aren't associated with any
> > particles. PS, the coloring of the outlines are based on the brightness
> of
> > the image at that point underneath it, which has been hidden. (Would be
> > happy to share the function if anyone wants it).
> >
> > Lastly, I tried adapting the circular hough transform example:
> >
> >
> http://scikit-image.org/docs/dev/auto_examples/plot_circular_elliptical_hough_transform.html
> >
> > But struggled with setting it up, due to a naive understanding of the
> > algorithm. Given that my image has thousands of particles, but I know
> > roughly the size distribution, would the circular hough transform be
> useful
> > to me?
> >
> > Thanks
> >
> >
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