Posted by
Julian Cooper on
Jul 18, 2009; 11:03am
URL: http://imagej.273.s1.nabble.com/longest-inscribed-lines-tp3690610p3690611.html
Dear Michael,
I am not sure whether this method will help but it seemed to reliably
isolate the grains when I tried it on your image.
1. Obtain two new images, one with horizontal edges detected and the other
vertical, from the original by Process>Filters>Convolve with kernels as
follows:
1 2 1 1 0 -1
0 0 0 2 0 -2
-1 -2 -1 1 0 -1
2. Invert the images
3. Use Analyze Particles on each image with default size, and circularity
0.0-0.5 (other values may be better but this seemed OK with your image so
that individual "dots" were excluded and grains remained. The Feret's
diameter appears to work then, as far as I can tell.
As a check I added the two masks, from the vertical and horizontal edge
images, together and this appeared very similar to the skeletonized version
of the original image but with thicker lines. I am not sure what happens if
the grains are aligned near to 45 degrees to the image boundaries, but that
didn't seem to be often the case in your image.
Kind regards,
Julian
> -----Original Message-----
> From: ImageJ Interest Group [mailto:
[hidden email]] On
> Behalf Of Michael Schmid
> Sent: 17 July 2009 11:50
> To:
[hidden email]
> Subject: longest inscribed lines?
>
>
> Hi everyone,
>
> maybe someone of you has a solution for the following problem:
> I have images of elongated martensitic grains, e.g.:
>
http://www.iap.tuwien.ac.at/~schmid/MartensiticGrains.png>
> I want to get some indication of the lengths of the grains to
> compare
> it with other images.
> The Fourier transform is dominated by the grain widths, so it does
> not help.
> Often, the grains are not separated but touch others, so caliper
> length (Feret's diameter) won't work either.
>
> A possibility would be searching for the "longest inscribed lines",
> i.e., the longest straight lines that fit into the foreground of the
> image, or even better, the longest line with a limited curvature (to
> follow slightly curved grains). Does anyone know about a plugin or
> some other transform/method that could do this?
>
> Thank you,
>
> Michael
>