: How do I brighten a part of a picture with Gimp? Say I wanted to bring out the colors in the shadowy bottom right hand part of the attached image, how would I go about it? I assume I

@Sent7350415

One year later:)

In fact on such image you want to use "Luminosity masks" that are progressive selections that cover the parts of the image within a given luminosity range. The good things about them is that the effect of the color tools apply in proportion to the lightness or the darkness of pixels so you never have visible transitions. There are scripts around that can generate the 5 canonical masks, but here is a quick demo with only two.


Duplicate the image
Colors>Desaturate and use Luminosity
Open the Channels list, and copy any of the RGB channels by dragging it to the main list. Rename the Channel "Highlights"
Duplicate the channel, and rename the copy "Shadows"
Colors>Invert to invest that channel.


Once this is done, you can work on the Highlights parts of the image by going to Channels, right-clicking "Hilights" and doing Channel to selection (and then reselecting the layer otherwise you'll be working on the selection channel). For instance, using this technique, I just dimmed a bit the highlights and lightened the shadows. No other adjustments necessary:



There is a more complete tutorial on the matter.

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@Lengel450

I use Magic Wand to highlight areas proposed to be changed and then use Curves

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@Dunderdale640

To restrict the processing to a part of the image you use a selection (Freehand selector, here). Once there is a selection most tools apply only to the selection. If you use that 'raw' selection there will be a very visible edge between the parts that were changed and those that were not, so to smooth the transition you usually feather the selection (this is an option ("Feather edges") in most selection tools, but it can also be done afterwards (menu Select>Feather)).

The simplest tool to use afterwards is Brightness/Contrast, but don't overdo it.

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@Vandalay110

For a smooth brightening (or darkening) of shadows (resp. highlights) I prefer the color curves tool (Shift+C) where you can define a non-linear curve for all channels, or a single RGB color channel.

In the example image I used a positive S-shaped curve for all values and a negative S-shaped curve to remove blue from the shadow parts of the image:

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