finding polygons in an image

[Sudheshna M]

Hi,

Can someone tell me how to find polygons in an image using imagej.

I have images with roughly many sided polygons, like in thermocol which is
closely packed polygons touching each other.
 I need to find
  - the sides of the polygons and
  - the angles at all vertices.

I want to do this in a macro, as there are many images.
Are there any plugins/ protocols in imagej for this?

thanks
Sudheshna

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html

[ctrueden]

Hi Sudheshna,

> I have images with roughly many sided polygons, like in thermocol
> which is closely packed polygons touching each other. I need to find
> - the sides of the polygons and
> - the angles at all vertices.

If the polygons are at a different intensity from the background (or you
can perform image preprocessing to coerce them somehow to a different
intensity), then you can:

- Threshold the image with Shift+T
- Create a selection (L, create selection)
- Press T to add the selection to the ROI Manager
- Click the ROI in the ROI manager, then press More > Split
- Delete the original ROI in favor of the split ones
- And then loop over the ROIs in the Manager to interrogate their
characteristics

You can determine the macro commands for doing this by using the Macro
Recorder (L, Record...)

Regards,
Curtis

On Mon, Oct 20, 2014 at 5:38 AM, Sudheshna Moka Muttana <
[hidden email]> wrote:

> Hi,
>
> Can someone tell me how to find polygons in an image using imagej.
>
> I have images with roughly many sided polygons, like in thermocol which is
> closely packed polygons touching each other.
>  I need to find
>   - the sides of the polygons and
>   - the angles at all vertices.
>
> I want to do this in a macro, as there are many images.
> Are there any plugins/ protocols in imagej for this?
>
> thanks
> Sudheshna
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
>

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html

[Gabriel Landini]

On Mon, Oct 20, 2014 at 5:38 AM, Sudheshna Moka Muttana wrote:

> Can someone tell me how to find polygons in an image using imagej.
> I have images with roughly many sided polygons, like in thermocol which is
> closely packed polygons touching each other.
>  I need to find
>  
>   - the sides of the polygons and
>   - the angles at all vertices.
>
> I want to do this in a macro, as there are many images.
> Are there any plugins/ protocols in imagej for this?

I want to be proved wrong here, but I think that you will struggle to find a
way of doing this from bitmaps unless you can find a way of extract the
polygon sides as straight lines from the image  (perhaps with a Hough
transform or similar?). If you can do that, then  finding intersections and
then the polygons and their sides and angles might  be doable.

However, from polygonal blobs of abitrary size and shape, the boundary is most
often not made of straight lines, but a chain of pixels. It might be difficult
to decide when it is a single irregular line or several chained smaller lines.

Perhaps looking at the contour convexity and concavity via multi-scale
contours in "scale space" would be helpful (look the the work of F. Mokhtarian
a few years back). Here is one of his papers, so you can get the idea:
http://www.cipprs.org/papers/VI/VI1997/pp008-015-Mokhtarian-1997.pdf

Please report here if you find a good procedure to do this.
Cheers

Gabriel

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html