[Gimp-user] how to obtain the same adjustment in GIMP like this one in Photoshop Express

[Cristian Secară <liste secarica ro>]

I played a bit with Adobe Photoshop Express in Windows phone and found
a useful adjustment that increases the gain in deep shadow portions,
while at the same time keeps *untouched* the already bright areas
(above a certain predefined level).

Here is a sample:
(original image)
http://www.secarica.ro/temp/test_808_original.jpg
(shadow increase to 100%)
http://www.secarica.ro/temp/test_808_photoshop_express_shadow_100.jpg
For the above image, the processing time when saving is about 11
seconds (on a 1.2GHz quad core Windows phone).

The application's adjustment looks like this
http://www.secarica.ro/temp/wp_ss_20170407_0003.png

I tried in GIMP various filters, effects, scripts, curves, fake HDR
etc. but with either I played with, there was always a slight change
also in the bright portions of the image.

What adjustment can be used to obtain the exact same result by using
GIMP ?

Here is another sample:
(original image - filename nokia_lumia_1020_10.jpg on this page
http://www.photographyblog.com/previews/nokia_lumia_1020_photos/ )
(shadow increase to 100%)
http://www.secarica.ro/temp/test_1020_photoshop_express_shadow_100.jpg

Thank you,
Cristi

-- 
Cristian Secară
http://www.secărică.ro