Posted by
Adrian Daerr-2 on
Jul 26, 2015; 11:40am
URL: http://imagej.273.s1.nabble.com/distinct-curve-positions-ascending-descending-tp5013739p5013764.html
Hello Rainer,
If pixel-precision is enough, this is what you can do:
- Image->Stacks->Reslice to get an image of your line profile
- Convolve with a kernel differentiating along your line (something like
-1 0 1 or its transpose, depending on how the result of Reslice is oriented)
- Threshold to isolate loci exceeding desired jump amplitude (positive
or negative)
- Save x,y coordinates of the thresholded pixels
If you use this to process a whole stack at once, be sure to rotate/flip
your thresholded picture so that points are saved grouped by frame
number (which after reslice becomes one of the screen coordinates).
If you need sub-pixel precision you can either scale the picture and use
a bigger differentiating kernel, or you have to write your own
correlation code (I can look for and send you some code I wrote a while
back if that helps).
cheers,
Adrian
On 2015-07-25 14:23, Rainer M. Engel wrote:
> Hello everybody..
>
> I'm working on a selection based on a plot profile (pixel values of a
> line), where I want to detect luminance jumps and differentiate between
> ascending and descending.
>
> Here is an example..
>
https://dl.dropboxusercontent.com/u/414433/imagej/plots.png>
> Green: ascending marked
> Red: descending marked
>
> Is there anything I can start from directly available in imagej/fiji to
> get these positions?
>
> Thanks in advance..
> Rainer
>
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