Yenya's World

Fri, 07 Apr 2006

Red eye reduction

A friend of mine asked me how to remove red eyes from photos. I use Gimp, and a plug-in that "just works". In order to show him which plug-in to install, I had to search where-T-F I've got the plug-in from. It seems that most web tutorials point to the same Script-Fu plug-in, which is based on a Linux Journal article.

This plug-in works the following way: you select a subset of the red eye, and the plug-in tries to expand it (using the fuzzy select tool), and then desaturate it. However, this results in a light-grey eye, instead of the dark eye. Not to mention that it is difficult to set the parameters correctly in order to find the whole red eye, but nothing more. There are images like the following one, where there is a wide variety of red eyes.

Red eye sample image

So I definitely cannot recommend the above plug-in. Instead, I use Robert Merkel's red-eye removal Gimp plug-in (which is based on an older plug-in for Gimp 1.x, written in Perl by Geoff Kuenning). See the source file for the installation instructions. This plug-in works in an opposite way - you select the superset of the red eye, and it tries to guess which part the red eye is. It results in a naturally-looking dark eyes, while it keeps the highlights intact. The only drawback is that its selection is not fuzzy, so in a full zoom the borderline between the pixels this plugin has changed and those which it didn't touch is clearly visible. However, for common resolutions it simply does not matter:

Red eyes removed

So I hope that the next time I can find this plug-in by greping my own blog instead of wasting my time with Google which points to the other plug-in almost exclusively :-)

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