>Apologies, I am new to GIMP - I am trying to figure out if there is a
>way to scale the image in GIMP using a ruler that is in the image. I
>have taken photos of a number of different fungi in the field and now
>I need to measure their size. In each photo there is a ruler (that
>goes both horizontally & vertically) in cm - so basically what I want
>is a way to tell GIMP that this part of the image is 1cm in size. Is
>this possible to do?
You need to adjust the Image -> Print Size resolution values to match the
captured ruler scale.
First set the canvas units to whatever you are using - cms The example I used is
millimetres. That is the drop down units menu (7) shown here:
Then use the Gimp measure tool to show the on canvas size. screenshot 1
measures 10 mm as 74.2 mm Use some guides if they help, the measure tool can
snap to intersections.
Then it is a matter of simple proportions to get a scaling factor in my case
74.2 / 10 = 7.42
Open up Image -> Print Size and multiply whatever resolution is there (mine is
180 ppi - comes from the photo) by the scaling factor. Do by hand or Gimp can do
simple arithmetic * multiplies / divides.
With that changed the measure tool should now show dimensions corresponding to
the image. screenshot 2
rich404 (via www.gimpusers.com/forums)
gimp-user-list mailing list
List address: firstname.lastname@example.org
List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list
List archives: https://mail.gnome.org/archives/gimp-user-list