Is there an easy way to select by histogram range in GIMP?

Question

The other day I was wondering if there is an easy way in GIMP to choose the pixels that are part of a selected range on the histogram.

Answer 1

Yes, it's possible to select by pixels' intensity range.

Step-by-step

1. Make a copy of the layer (Layer → Duplicate Layer)
2. Select the duplicate layer, apply threshold (Colors → Threshold) to select the range of intensities.
3. In Layer → Mask → Add Layer Mask (or right click in the list of layers). Select “Grayscale copy of layer” and “Invert mask”.
4. idem: Mask to selection.
5. Hide or remove the layer with mask.

An example:

Original image. I want to select the circle:

Make a copy of the layer:

Apply threshold. Note that the area to be selected is black:

Add Layer Mask using the grayscale value of the image:

Now you've obtained an image with the mask. Everything except the black circle is transparent (we can see the bottom layer through it):

Convert the mask to selection. Switch to the original layer. The circle is selected.

Answer 2

There is a plugin called Adagio Range Selection that does pretty much what you want. You can't select from the histogram directly, but you can select the upper and lower boundaries.