Lena,
The discrepancy isn't really a discrepancy, but the explanation is hidden
in the type of selections the two tools create. The Freehand Selection
tool, when you draw a line, automatically connects the two endpoints and
creates an *area* selection. The Freehand Line tool creates a *line*
selection that follows your tracing, but does not connect the endpoints.
The easiest way I can think of to illustrate this is to create an
uncalibrated image (do a Set Scale..., and click the "click to remove
scale" button if necessary), then draw a Freehand Selection and measure
Area and Length. You'll see an area in number of "square pixels" (roughly
equal to the number of pixels enclosed by the selection), and a length of 0
(zero). Then use the Freehand Line tool and measure the same way. Now the
selection has a length (again, roughly the number of pixels) and it now has
an area that is very close to the length--it's the area of the selection,
length x 1 pixel wide.
The same thing applies with a length-calibrated image, but the numbers make
it more difficult to observe. Hope this makes sense.
On Wed, May 6, 2015 at 3:04 PM, Lena-Christin Conradi <
[hidden email]
> wrote:
> Dear all,
>
> maybe someone can help me to answer the following question:
>
> I am wondering about the difference between the "freehand selection"-tool
> and the "freehand line"-tool! With both you can measure and quantify areas
> of an image. The area count gives you different values, which is okay,
> since you can also choose between 'pixel' and e.g. 'micrometers'.
>
> However the problem that I encountered:
> If you select an area and then another area which as approximately 50% of
> the size of the first one it gives you with the "freehand selection"-tool
> about 50% of the first value. However with the "freehand line"-tool I am
> getting values of far more than 50%.
>
> I would be very grateful for some explanation/advice.
> Thanks,
> Lena
>
>
>
>
>
>
> --
> _______________________
>
> Lena-Christin Conradi, MD
> VIB3 - Vesalius Research Center
> KULeuven Campus Gasthuisberg
> O&N4 Herestraat 49
> B-3000 Leuven
>
>
http://www.forschungskolleg-crc.med.uni-goettingen.de>
http://www.vrc-lab.be>
> --
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Research Associate
Sealed Air Corporation
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