Hack 9. Remove Red Eye from Photos
Follow a few basic steps with the GIMP to remove red eye from photos.
Red eye happens to the best of us. Nowadays many cameras have red-eye reduction features, but whether you are dealing with older scanned-in photos, or you just forgot to turn on that feature, sometimes you get digital photos that have red eye in them. Since red eye seemingly turns even the sweetest child into demon spawn, you generally want to remove it from your photos before you send them out to relatives. Although it might seem as if you need extensive experience and expensive tools to edit your photos, with the GIMP you can take out red eye in a few simple steps.
The basic steps in this procedure are to select the red area of the eye and then open the channel mixer and change the red, green, and blue values until the red eye looks like a normal pupil. The specifics of these steps are a bit more involved, but as you'll see, they mostly require a bit of time and tinkering.
1.10.1. Select the Red Eye
First you need to select the red eye. Zoom in your image (hit the + key) until the part of the picture with the red eye is mostly filling the window. There are a number of ways to select the red part of the eye, but the fuzzy selection tool is the easiest to use.
The simplest way to select the red part of the eye is to go into the different color channels and disable all but either the green or the blue color channel. Click File Dialogues Channels, and click both the red and blue channels so that only the green channel is selected (alternatively, you can select only the blue channel). Now click the eye icon next to the red channel so that you see only the blue and green channels in the image.
Change to the fuzzy selection tool (hit the Z key or select the tool from the toolbar) and click on a red portion of the eye. The first time you do this, you probably won't select all the red, so cancel the selection with Ctrl-Shift-A. Then go to the fuzzy selection tool settings window, make sure feather edges is turned on, increase the threshold, and try again. This part of the process probably requires the most tinkering, so just try different threshold values until you select all of the red. Once you have it right, hold down the shift key and click on a red section of the other eye to select it, too. Now you can go back to your channels and turn on visibility for the red channel and make sure that all three color channels are on. With both eyes selected, you can move on to taking out the red.
1.10.2. Take the Red Out
To take the red out of the selected area, right click on the image and select Filters Colors Channel Mixer. The channel mixer lets you adjust the levels of red, green, and blue in the image. Youll definitely want to move the red levels down, and then move the green and blue levels up. Turn on the preview and experiment with the settings until the eye in the preview looks normal. You'll likely want to turn up green the most, then blue, then red. When the eye looks right, click OK to see the changes applied to the image. If it isn't quite how you want, hit Ctrl-Z to undo the change, go back, and try again until it's right. Once you are satisfied with the change, click File Save.