Posted by
Herbie on
Oct 02, 2019; 1:45pm
URL: http://imagej.273.s1.nabble.com/how-does-ImageJ-measure-circular-ROI-tp5022481p5022482.html
Good day,
this is a cross-post from the IJ-Forum:
<
https://forum.image.sc/t/how-does-imagej-measure-pixels-in-circular-roi/30041>
Please make sure that you understand what spatially discrete, i.e.
sampled images mean. The fill command acts on the samples not the ROI
circle that is a vector graphic. The number of pixels that are filled
most likely depends on the next neighbor distances.
Furthermore please not that pixels have no spatial extension, i.e. what
you see as squares of equal gray is the common attempt (most simple
interpolation scheme) to visualize the sample value. Per convention
ImageJ assumes the sample coordinate at the upper left corner of the square.
Did you consider to oversample your image using an adequate
interpolation scheme?
Regards
Herbie
::::::::::::::::::::::::::::::::::::::
Am 02.10.19 um 15:18 schrieb Charitra:
> I am trying to measure photon counts from single molecules (7*7 pixels) by
> defining a ROI around the single molecule. I localize the center of the
> emitter (this could be subpixel) from ThunderSTORM and draw the ROI around
> it which makes everything sub-pixel. If the ROI is circular, some of the
> pixels are excluded from measurement. Can someone tell me how exactly the
> pixels for measurement are selected? Is it based on the amount of area
> selected by the ROI boundaries or is it something else?
> <
http://imagej.1557.x6.nabble.com/file/t382433/IMG_20191001_172953.jpg>
> <
http://imagej.1557.x6.nabble.com/file/t382433/IMG_20191001_173241.jpg>
>
> In the above images, I specified a sub-pixel center and drew a circular ROI
> and filled it from the ROI Manager, but the fill seems to fall completely at
> a different location than the ROI specified. I am not able to understand how
> this works! Please help.
>
>
>
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