Published at LXer:

Warped horizon lines and bent skyscrapers are just as disheartening to the travel photographer as the demonic "red eye" effect. Red eye correction is commonplace in software today, but you don't have to live with distortion either. Free software can correct lens- and perspective-distortion, turning the fishbowl look into the landscape as you remember it. And even if you don't have vacation pictures that need a new perspective, the same technique can come in handy elsewhere -- such as for extracting undistorted textures from a photo to use in a game or 3-D model. Here's how to do it.

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