When flash illumination is used for the capture of an image sometimes the pupils of people in the image appear red. This is caused by light from the flash unit entering the pupil, multiply reflecting off the retina, and finally exiting back through the pupil. Because light is partially absorbed by capillaries in the retina the pupil appears red in the image. This phenomena is referred to as "redeye." The probability of redeye being observed increases the closer the flash unit is to the optical axis of the lens. Therefore, redeye is commonly observed in images captured by a small camera with an integral flash unit.
Commonly assigned U.S. Pat. No. 5,432,863 describes a user-interactive method for the detection of objects in an image that have the color characteristic of redeye. This method automatically detects candidate redeye pixels based on shape coloration and brightness.
Although the presently known method of detecting redeye is satisfactory, it is not without drawbacks. The method of U.S. Pat. No. 5,432,863 does not determine whether the candidate pixels are located in a face or are part of a human eye.
Consequently, a need exists for detecting redeye that overcomes the above-described drawbacks.