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

Hi,

may be it is better to you to use ImageJ for this work (http://rsbweb.nih.gov/ij/).

Best, Alexander

Sun, 22 Jan 2012 20:10:21 +0100 Dutch-User

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!

-- Dutch-User (via gimpusers.com)
_______________________________________________ gimp-user-list mailing list
gimp-user-list@gnome.org
http://mail.gnome.org/mailman/listinfo/gimp-user-list

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.

:o)

Steve

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