Hi Stein,
you can use the Wand Tool to select an area with the initial pixel value
(where the click was) plus/minus some tolerance. Double-click the Wand
Tool to set the tolerance.
Then fill the selected area by Edit>Fill (simply type 'f' or ctrl-f) or
Process>Math>Set.
In contrast to the changeValues macro function mentioned by Wayne, this
only affects connected pixels (the Wand options allow you to select
4-connected or 8-connected).
For 3D, there is a 3D Wand with adaptive (automatic) tolerance at
http://yawi3d.sourceforge.net/but I have no experience with it, and I don't know whether it is
possible to create stack slice selections with it.
Michael
________________________________________________________________
On 2017-02-17 10:53, Stein Rørvik wrote:
> The flood fill tool fills any connected regions having the exact same
> greyscale pixel value as the source pixel.
>
> Is there any plugin or tool that does the same, but instead fills
> adjacent pixels having values within a certain threshold?
> That is, if the source pixel has value say 50, any connected regions
> with a value between say 45 and 55 would be filled.
> I need this both for 2D and 3D; but 2D is most important.
>
> In the old NIH Image for Mac classic OS, you could do this quite
> easily by setting an upper and lower threshold, and then flood filling
> from a point within the thresholded region while the threshold is
> active. Then all connected pixels within the threshold would be flood
> filled.
>
> Stein
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