When the Area is Completely White
If you have no image information, and the highlights are pure white, then you need to create a channel mask. Create a copy of the first image by pressing Ctrl + D.
Now, go to Image, Colors and Threshold. Select the extreme highlights of the histogram. Your white colors will turn completely white, and the rest of the pixels will be black.
Next, select the original image again, and hit Ctrl + L to open up the Layers and Channel dialog box. Select the Channels tab, and create a new channel. Click back on the threshold image, and hit Ctrl + A and then Ctrl + C.
Edit/Paste this image onto the first image. Click on the Layers tab, and then anchor the floating image. Close the threshold image since you won’t be needing it anymore.
Go back into Channels tab, and right-click on the new channel. Press Ctrl + S, and then go to Select and Feather. Generally, you want the feather value to be around 15. You may want to adjust this further, but 15 should be fine for most selections.
You should now go back into the Layers tab. Click on the Background layer. You can now start grafting back in the pixels that you lost in the previous processes.
Click on the clone tool. Clone a section of the image that most closely matches the mixing pixels, and zoom in to make sure that you fill the entire area. The new section will standout a bit from the background. Use the smudge and airbrush tools to adjust the edges of the selection.
As you can see, GIMP is very effective at correcting overexposed photos. The program has a lot of features, and it really doesn’t take up a lot of room on your computer, unlike traditional Photoshop. Plus, you can’t beat the price of the program – free. While you may get frustrated by some lack of capabilities in GIMP, the program is really effective with a lot of different edits, including fixing photos that are too bright.