Re: Threshold bug

Posted by Gabriel Landini on Mar 11, 2016; 3:42pm
URL: http://imagej.273.s1.nabble.com/Threshold-bug-tp5015854p5015855.html

On Friday 11 Mar 2016 15:35:56 Ed White wrote:

> I have a 32bit image on which I perform a threshold using the Huang
> algorithm. For my particular example using Huang applies a threshold to
> pixel values between -3586.43 and 260.45. While previewing the threshold
> (looking at the red overlay of thresheld pixels), I zoom in on the image
> and check individual pixel values. To my surprise, I find that some pixels
> slightly above the 260.45 threshold are red in the preview, as well as all
> those below 260.45 (by slightly above, I've seen values up to 266
> included). When I actually apply the threshold it seems to be done
> properly; in other words, those pixels displayed in red that were above
> 260.45 are not included when the operation is preformed. To summarize, on
> single images the bug appears to 'make red' some incorrect pixels while
> previewing the threshold.

Hi,
The display of the 32 bit image histogram is done on 8-bit space. That is not
a bug, but a way of displaying a binned histogram.

Cheers
Gabriel

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