Re: [Gimp-user] Calculate area and diameter

[Stefan Maerz <stefanmaerz gmail com>]

On 01/22/2012 04:32 PM, Steve Kinney wrote:
> On 01/22/2012 03:59 PM, Stefan Maerz wrote:
> > A while ago I calculated area by creating a transparent layer and
> > painting with a brush the locations that I wanted to include in
> > the area. Then using GIMP's histogram (color>Info>histogram), I
> > got a pixel count for that new layer. (Side note, make sure you
> > have the right layer selected in the layers dialog)
> >
> > Then I used a proportion ( Pixels:Inches ) that I got from a scale
> > in the image to calculated area.
> WOW, I thought I knew some clever tricks but this one wins the
> prize!  In the case at hand, Select By Color with suitable threshold
> adjustments in the Tool Options tab, followed by Colors>  Info>
> Histogram should do the trick.  I just checked and if there is a
> selection, the Histogram tool only looks at that.
That is even simpler than my suggestion. In my case it wouldn't have 
worked because the colors did not contrast.

An (perhaps simpler) alternative would be to use the "Ellipse Select 
Tool" in the Toolbox to get a selection.

-Stefan Maerz