Segmented line shifting when splining in subpixel mode

[Pierre1981]

Hello,

I observed something which is a little bit puzzling when using sub-pixel resolution:

1/ I check "true" for Sub-pixel resolution in Edit>Options>Profile Plot Options
2/ I make a segmented line selection:



3/ I apply "Spline Fit" by checking the Spline Fit check box:



The result is that segment is overall shifted in one direction by about one pixel (on the example "anchor points" are translated toward the left, which does not happen out of sub-pixel mode).
However, if I then uncheck Spline Fit, the resulting segmented line is different from the first selection I made:



4/ If now I interpolate the spline fit with one pixel interval, I again see quite some difference from the original spline, with what seems to be a global selection translation (sometimes one or two pixel distant from the original selection; this appears also without sub-pixel resolution).



In my application this is a little bit annoying, because I look at intensity along curved lines and I need to adjust the selection after splining and after interpolating.

Is all this normal, or shouldn't there be a need to be fixed?

Kind regards,
Pierre

[Michael Schmid]

Hi Pierre,

did you try to update ImageJ to 1.48g or the latest daily build?

The accuracy of line displays has improved a lot in the recent versions.
If there are still problems, please post to the list again.

Michael
________________________________________________________________


On Dec 2, 2013, at 15:58, Pierre1981 wrote:

> Hello,
>
> I observed something which is a little bit puzzling when using sub-pixel
> resolution:
>
> 1/ I check "true" for Sub-pixel resolution in Edit>Options>Profile Plot
> Options
> 2/ I make a segmented line selection:
>
> <http://imagej.1557.x6.nabble.com/file/n5005762/new_selection.jpg>
>
> 3/ I apply "Spline Fit" by checking the Spline Fit check box:
>
> <http://imagej.1557.x6.nabble.com/file/n5005762/spline_copy.jpg>
>
> The result is that segment is overall shifted in one direction by about one
> pixel (on the example "anchor points" are translated toward the left, which
> does not happen out of sub-pixel mode).
> However, if I then uncheck Spline Fit, the resulting segmented line is
> different from the first selection I made:
>
> <http://imagej.1557.x6.nabble.com/file/n5005762/after_spline.jpg>
>
> 4/ If now I interpolate the spline fit with one pixel interval, I again see
> quite some difference from the original spline, with what seems to be a
> global selection translation (sometimes one or two pixel distant from the
> original selection; this appears also without sub-pixel resolution).
>
> <http://imagej.1557.x6.nabble.com/file/n5005762/interpolate.jpg>
>
> In my application this is a little bit annoying, because I look at intensity
> along curved lines and I need to adjust the selection after splining and
> after interpolating.
>
> Is all this normal, or shouldn't there be a need to be fixed?
>
> Kind regards,
> Pierre
>
>
>
>
> --
> View this message in context: http://imagej.1557.x6.nabble.com/Segmented-line-shifting-when-splining-in-subpixel-mode-tp5005762.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

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[Pierre1981]

Hi Michael,

Thanks for your answer.
Wayne solved the issue in yesterday daily built.

Kind regards,
Pierre