Is it possible to select a tonal area in histogramm in a filter?


#1

Out of curiosity. Would it be possible in Gmic to have a filter where you can chosea a tonal area by selecting a left and right point in a histogram?
How the left and right points are selected is irrelevant. Could be by clicking in the histogramm or by slideres…


(Jean Pierre “Xaos52” De Schacht) #2

Filters > GMIC > Lights and shadows > Slice Luminosity

already allows you to do this, be it by specifying numerical ranges…


#3

Ok thanks, that’s interesting.
And could a histogramm be displayed?
To choose tonal areas I often find a histogramm to be very useful.


(Kevin Payne) #4

Isn’t that what the Threshold tool effectively does?


(Using GIMP)


(Jean Pierre “Xaos52” De Schacht) #5

I presumed all tonal differences within the range had to be preserved.


#6

Basically yes I’d like to select a left and a right limit. This could be done with the threshold tool.

I see I need to be more specific.
I’d like to use select a tonal range. The histogram I want because I find it easy to see the edge of a tonal region in a histogram. Imagine a bright sky with a dark foreground, you can easily discern the two peaks in a histogram.
Then I want to use the selected values to do some computation using overlay layers and masks.

This is a procedure I’m experimenting with so I was wondering if this could be automated using Gmic.


(Kevin Payne) #7

How about -

create the layer mask from a Greyscale copy of the layer.
Use the threshold tool on the layermask

You may find it’s better to use the curves tool instead of the threshold tool to give you gradual transitions


#8

Yes.

I think I will work my idea out a little better and do a thorough post here later. So it will be easier understand what I’m trying to accomplish.