I admit it.

I yam a GIMP oddista. I use the GIMP to create black-and-white heightmaps/depthmaps which ultimately end up as models to be cut out in 3D on a CNC machine.

Wacky stuff.

Don't disagree.

But--wow--what a tool GIMP is for me! Even if from sophisticates's point-of-view all I do is grab it on its wrong end and whack-whack-whack. You maybe can't tell by looking at my posts, but I use GIMP in tres mucho sofisticated ways too.

"So I was wondering" [here it comes...] "how hard it would be" (that is, if someone could coach me through it) "to create a script or plug-in that could update the display of the min and max values of the pixels enclosed by an arbitrary selection, as it (the selection) was changed dynamically."

It may be that this is already known to aficianadoes in these parts as a Wicked Problem. If so, I will be glad to know it, because I just came here to let you, my friends, know that, if you do not help me, I am going to set off into the Land of Scripts and Plug-ins--without a decent flashlight--and you may never hear from me ever again, ever, and well, I just wanted to thank you for all your help you have gaven me and tell you how much you all have meant to me over the years and well, I hope somebody can think of an easy way to do it here because well, I really don't want to go back in There!

So long.

ur freind.

You can't really do that with a script. That would be an extension of the current selection tools (rectangle/ellipse/freehand) but even then these currently only compute the true selection when you tell them you are finished...

(Whoops, I replied to a reply that morphed! ;^) )

I followed up on the new information (for me) that Histogram supplied that info already--and it altmost does.

I open the Color->Info->Histogram window and draw a selection, and the histogram is updated every time I stop adjusting the selection.

I see that it gives me the Mean, Std. dev., Median, #Pixels, Count, and Percentile.

However, it only shows min and max as "positions" along a line (which has bothered me before). I have to adjust the sliders Left-Right and keep my eye on the percentile change to see, exactly, where the min and max are. Histogram knows what they are--it draws lines at those locations: I wish it would write them out too.

(Maybe I could calcalate it from the Mean, Median, and Std. dev... [Checks calendar] Nope. Not enough decades left.)

Thanks, ofnuts!

gramp, have a look at, ImageJ or GNU Octave.

There is a gimp-histogram function in the PDB that returns this information.

So you can use a dichotomic search in min and max to find those values that make count<>pixels.

Edit: quick hack, see attachment. Values can be off by one but I have to deal with other code right now.

If you decide to visit the land of scripting, the following two functions might be of use. The channel passed to the function is the same as used by the 'gimp-histogram' procedure (i.e., HISTOGRAM-VALUE, HISTOGRAM-RED, HISTOGRAM-GREEN, HISTOGRAM-BLUE, HISTOGRAM-ALPHA, or HISTOGRAM-RGB).

Thank you friends for rallying round.

@Odinbc "Right tool for the job." I fired up imagej (strangely, I didn't have it on this my main machine, but use it somewhat regularly on the others). Analyze->Histogram brings up the window with a promising-looking "Live" button.

I can draw a selection of my desired size and aspect, and drag it around with the "Live" button activated, ImageJ shows me a real-time histogram and identifies the min and max at the same time. (Just like in my dream.) Thank you.

Edit: BTW, I discovered that holding the Shift key will maintain the aspect ratio as the selection is resized with the mouse: important feature for me.

@Ofnuts Bringing it to GIMP. [For the sake of archive-ness] I installed the script (after making it executable and looking into it to see its registered location) in plug-ins/, ran Filters->Script-fu->RefreshScripts, but didn't see it (because I think I didn't scroll down far enough), but found it right away after restarting GIMP: Filters->Find min and max in drawable...

I create a selection initially, or move it, and then select the minmax filter, and the min/max values display for me on the bottom-most (sorry, don't know the name) line of the image window, but with a "Danger" sign (red/white triangle with '!').
Incidentally, the high value reported is off by -1 (e.g., 254 instead of 255), and the low value is off by +1 (1 instead of 0).

This is a huge improvement over the nothing that I had before, and is plenty useful as it is, but does require repeating the filter after each move instead of updating the min/max continuously during movement. [Again, just recording this for archival purposes. As you said, "quick hack", which for me demonstrates the feasibility, for which thank you.]

@SaulGoode

Whene'er I have ventured into ScriptLand, I have so far, always, headed perpendicularly away from the Great Gray Mist. ;^)

Thank you. Again, if you'll leave them here, one of my future selves is sure to come hunting them (after we get over our irrational fears).

Gimp considers all messages from plugins/scripts as "Warnings".

I think the better part of valor here is to follow Odinbc's advice and use ImageJ.

Not to push for Emacs-like expectations from GIMP, but if anyone does add ImageJ-like live-histogram capability to GIMP, please let me know.

Again, I'm thanking you, like Mrs. Nussbaum from Allen's Alley, for answering my plea already.