[R] shapes of woodpeckers' cavities

PIKAL Petr petr.pikal at precheza.cz
Fri Mar 7 13:10:57 CET 2014


Hi

Another option can be to use e.g. ImageJ and compute fractal dimensions of the outline.

Petr

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Jim Lemon
> Sent: Friday, March 07, 2014 12:04 PM
> To: Violette BERTRAND
> Cc: r-help at r-project.org
> Subject: Re: [R] shapes of woodpeckers' cavities
>
> On 03/07/2014 08:51 AM, Violette BERTRAND wrote:
> > Hi,
> >
> > I have pictures (.png) of the shape of many entrances of woodpeckers’
> cavities, coloured in black. I want that R takes these pictures and
> stacks (superimposes) all the shapes to determine the tendency of the
> shape of cavities for each species of woodpecker.
> >
> > I currently use the package EBImage which determine the mean radius
> of the shape of entrances (the shape is divided in 8 parts, and the
> package measure the mean radius for each part). So this package uses
> only the mean radius for each part of the shape.
> >
> > But, I would like that R use the real shape of cavities. Is another
> package exists, which will use the real shape of my pictures ?
> >
> Hi Violette,
> I think that this is more of a graphics manipulation. You can get the
> outline of the woodpecker hole by:
>
> 1) loading your image into the GIMP
> 2) duplicating it
> 3) scaling the duplicate down by about 2.5%
> 4) select the area using "similar colors"
> 5) bucket fill the selected area with white
> 6) copy the selected area
> 7) paste it onto the original image
>
> You will then have the outline as in the image attached. I don't know
> whether the GIMP will do it, but there are image compositing functions
> that will produce an average of many images. There you have your
> average woodpecker hole.
>
> Jim

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