Re: how to mark single pixel in a overlay

Posted by Jeremy Adler on Jan 08, 2016; 9:36am
URL: http://imagej.273.s1.nabble.com/how-to-mark-single-pixel-in-a-overlay-tp5015334p5015344.html

Herbie and Volker,
Thanks for responding.

I appreciate that a pixel is a value in a array that makes up an image but in a zoomed image on a screen appears as a square of pixels with the same intensity.

makePoint()  only marks the top left of the zoomed pixel

My point is that there seems to be no simple way of marking the version of the single pixel  on the screen version of the image in a way that unambiguously identifies it - by outlining it. And it would be useful and plausible addition to the existing overlay options.

There are complex ways of marking a single pixel - briefly give it value different from all other pixels, threshold it and create a ROI - this does outline the whole zoomed pixel, oddly unlike makePoint(), and afterwards restore the original value and convert ROI to an overlay. Or I could increase the size of image by replicating pixels and draw lines around the pixel. But these solutions lack elegance.

Alternatively the pixel inspection tool mostly does what I want - to see pixel values in small area with the coordinates shown - is there a way within a macro to set the position and change this location of the centre of the Pixel Value window, or even to concurrently have more than one Pixel Value window running ?

So really this is mostly plea for an additional overlay drawing option.

-----Original Message-----
From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of Volker Baecker
Sent: den 7 januari 2016 14:35
To: [hidden email]
Subject: Re: how to mark single pixel in a overlay

Hello,
maybe you could use

makePoint(x, y);
Overlay.addSelection;
run("Select None");

to add a point selection to the overlay.

Volker


Jeremy Adler:

> I am want to use the overlay to mark a single pixel in an image that has been zoomed to show individual pixels - within a macro.
>
> But I cannot see how to mark a single pixel in the overlay.
> Overlay.drawRect   marks an area of 2x2 pixels centred on my target pixel but 1x1
> Overlay.drawLine  with the two positions set the same, marks a single pixel offset
>
> I can mark a single pixel using the ROI manager and then move it and convert it to an overlay, but this seems unduly cumbersome, is there a better way of marking single pixels in a overlay ?
>
>
> Dr Jeremy Adler
> Senior res engineer
> BioVis
> Dag Hammarskjölds väg 20
> Uppsala Universitet,  752 37 Uppsala ,Sweden
>
>
>
> [phone]
>
> http://www.biovis.uu.se
>
>
>
>
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> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
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