Red eye reduction technique

Abstract

A red-eye reduction technique includes converting a multi-channel image to a hue, saturation, value color space. The hue channel, the saturation channel, and the value channel are processed to identify the location of the red-eye within the image, if any.

1 . A method to identify sub-regions of a multi-channel image as containing red-eye, said method comprising the steps of:
 (a) converting said multi-channel image to a modified multi-channel image wherein at least one of said channels is an enhanced luminance channel that has more than 60% of the luminance information of said multi-channel image and at least one of said channels is a saturation channel;   (b) deriving a spatial flash mask by applying a luminance threshold operation to said enhanced luminance channel, said spatial flash mask identifying regions of said multi-channel image potentially affected by a flash;   (c) masking said saturation channel with said spatial flash mask to derive a masked saturation channel;   (d) deriving a saturation mask by applying a saturation threshold to said masked saturation channel;   (e) identifying red-eye using said saturation mask and removing the identified said red eye from said multi-channel image.   
     
     
         2 . The method of  claim 1  where said saturation mask compares the standard deviation of the saturation value of a respective pixel to a threshold. 
     
     
         3 . The method of  claim 2  wherein said standard deviation of said saturation value measured relative to the mean saturation of pixels in a neighborhood local to said respective pixel. 
     
     
         4 . The method of  claim 3  wherein said saturation channel represents the relative bandwidth of the visible output from a light source 
     
     
         5 . The method of  claim 1  where said flash mask identifies spatial boundaries around regions of said image affected by a flash. 
     
     
         6 . The method of  claim 1  where said flash mask is derived at least in part by use of a convex hull technique. 
     
     
         7 . The method of  claim 1  where said flash mask comprises a first region of said image having a first set of pixels that satisfy said threshold operation, a second region of said image having a second set of pixels that satisfy said threshold operation, and a third region of said image having a third set of pixels that does not satisfy said threshold operation. 
     
     
         8 . The method of  claim 7  where said third region is constructed so as to be contiguous with both said first and second region. 
     
     
         9 . A method to identify sub-regions of a multi-channel image stored on a computer-readable medium operably interactive with a processor, said multichannel image containing red-eye, said method comprising the steps of:
 (a) said processor converting said multi-channel image to a modified multi-channel image including a luminance channel, a saturation channel, and a hue channel;   (b) said processor masking at least one of said saturation channel and said hue channel with a flash mask, said flash mask determined by applying a threshold operation to respective pixels of said luminance channel and by computing spatial bounds around those said pixels that satisfy said threshold operation;   (c) said processor determining pixels representing red-eye from said masked at least one of said saturation channel and said hue channel; and   (d) said processor correcting said red-eye and storing the corrected said image on said computer-readable medium.   
     
     
         10 . The method of  claim 9  where said flash mask is used to mask said saturation channel, said processor determining a saturation mask from the masked said saturation channel, and using said saturation mask to mask said hue channel so as to determine said pixels representing red-eye from said masked hue channel. 
     
     
         11 . The method of  claim 10  where said saturation mask is determined by applying a second threshold operation to respective pixels of said saturation channel and by computing spatial bounds around those said pixels that satisfy said second threshold operation. 
     
     
         12 . The method of  claim 10  where said saturation mask compares the standard deviation of the saturation value of a respective pixel to a threshold. 
     
     
         13 . The method of  claim 12  wherein said standard deviation of said saturation value measured relative to the mean saturation of pixels in a neighborhood local to said respective pixel. 
     
     
         14 . The method of  claim 13  wherein said saturation channel represents the relative bandwidth of the visible output from a light source. 
     
     
         15 . The method of  claim 9  where said flash mask is derived at least in part by use of a convex hull technique. 
     
     
         16 . The method of  claim 9  where said flash mask comprises a first region of said image having a first set of pixels that satisfy said threshold operation, a second region of said image having a second set of pixels that satisfy said threshold operation, and a third region of said image having a third set of pixels that does not satisfy said threshold operation. 
     
     
         17 . The method of  claim 16  where said third region is constructed so as to be contiguous with both said first and second region. 
     
     
         18 . A method to identify sub-regions of a multi-channel image stored on a computer-readable medium operably interactive with a processor, said multichannel image containing red-eye, said method comprising the steps of:
 (a) said processor converting said multi-channel image to a modified multi-channel image including a luminance channel, a saturation channel, and a hue channel;   (b) said processor masking at least one of said saturation channel and said hue channel with a flash mask, said flash mask comprising identified spatial boundaries around regions of said image potentially affected by a flash;   (c) said processor determining pixels representing red-eye from said masked at least one of said saturation channel and said hue channel; and   (d) said processor correcting said red-eye and storing the corrected said image on said computer-readable medium.   
     
     
         19 . The method of  claim 18  where said spatial boundaries are identified using a connected component technique. 
     
     
         20 . The method of  claim 19  where said connected component technique is a convex hull technique.