Re: [Gimp-user] Calculate area and diameter

[Stefan Maerz <stefanmaerz gmail com>]

On 01/22/2012 01:10 PM, Dutch-User wrote:
> Hi everyone. In my collection of pictures, I found GIMP useful and easy to measure the diameter of a 
> near-round coloured object. However, since the objects are not exactly round, I have to measure a few times 
> and than guess for the average diameter. Now I've seen there's a way to select these objects by the colour 
> they have. Does anybody know if there's an easy way to have GIMP tell me the overall area of the object, and 
> the mean diameter?
>
> Thanks!
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.

There might be a easier way to calculate area since you have simple 
shapes, but this worked perfectly for me, because my shapes were highly 
irregular and needed human interaction to determine what should be 
measured and what shouldn't be.

HTH,
-Stefan Maerz