US 6,728,401 B1Granted

Red-eye removal using color image processing

AssigneeViewAhead Technology, Inc.

InventorJon Y. Hardeberg

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Abstract

A color processing system is provided that corrects color artifacts such as red eye typically formed in images from a camera flash. An image is captured or processed by inputting the image into the system. To correct red eye artifacts, a “redness” mask is computed by calculating the colorimetric distance, in an approximately perceptually linear color space, between a prototypical reference “red eye” color and each pixel of the image, or a selected portion thereof, containing the red eye. Each pixel of the redness mask is then reduced to one of two values by comparing the calculated colorimetric distance recorded by each mask pixel to a threshold value. Various filtering, morphological, and blob analysis techniques may be applied to the mask to eliminate noise, reduce errors, and facilitate a more natural look. The mask serves to identify pixels in the color image needing correction, and further serves to identify the amount of correction needed. Pixels identified as having red-eye artifacts are modified to a substantially monochrome color. The bright, substantially white, specular reflection of the eye, however, is preserved.

Claims17

Dependent claims

An artifact correction system that corrects an artifact having a plurality of color characteristics comprising:

image capture circuitry that captures a color image;
signal processing circuitry that receives the color image from the image capture circuitry, compares at least a portion of the color image to at least one reference color characteristic to identify the artifact, and modifies at least one of the plurality of color characteristics of the artifact;
memory that stores the color image in its raw and processed states;
and
wherein the signal processing circuitry compares the plurality of color difference values between at least a portion of the color image and the at least one reference color characteristic to at least one threshold value to compute a mask representing a plurality of pixels, where each pixel is represented by one of only two discrete end values, a plurality of pixel blobs are created having common values, the artifact has an expected pattern, the signal processing circuitry performs morphological, blob-detection, and pattern-recognition operations on the mask to select an artifact-identifying blob out of the plurality of pixel blobs corresponding to the expected pattern of the artifact, the artifact-identifying blob of the mask has a periphery, the signal processing circuitry performs a smoothing operation on the artifact-identifying blob to introduce a plurality of intermediate values to the mask along the periphery of the artifact-identifying blob, and the signal processing circuitry modifies the at least one of the plurality of color characteristics of the artifact in proportion to the end values and intermediate values that represent the pixels of the mask.

2 more elements

An image processing system that corrects an artifact having a plurality of color characteristics, in a color image, comprising:

signal processing circuitry that compares at least a portion of the color image to at least one reference color characteristic to identify the artifact, and modifies at least one of the plurality of color characteristics of the artifact to correct the artifact;
and
wherein the signal processing circuitry compares a plurality of color difference values between at least a portion of the color image and the at least one reference color characteristic to at least one threshold value to compute a mask representing a plurality of pixels, where each pixel is represented by one of only two discrete end values, a plurality of pixel blobs are created having common values, the artifact has an expected pattern, the signal processing circuitry performs morphological, blob-detection, and pattern-recognition operations on the mask to select an artifact-identifying blob out of the plurality of pixel blobs corresponding to the expected pattern of the artifact, the artifact-identifying blob of the mask has a periphery, the signal processing circuitry performs a smoothing operation on the artifact-identifying blob to introduce a plurality of intermediate values to the mask along the periphery of the artifact-identifying blob, and the signal processing circuitry modifies the at least one of the plurality of color characteristics of the artifact in proportion to the end values and intermediate values that represent the pixels of the mask.

A method for correcting an artifact, having a plurality of color characteristics in a color image comprising:

comparing at least a portion of the color image to at least one reference color characteristic to identify the artifact;
modifying at least one of the plurality of color characteristics of the artifact;
comparing a plurality of color difference values between at least a portion of the color image and the at least one reference color characteristic to at least one threshold value to compute a mask representing a plurality of pixels, where each pixel is represented by one of only two discrete end values;
creating a plurality of pixel blobs having common values, where the artifact has an expected pattern;
performing morphological, blob-detection, and pattern-recognition operations on the mask to select an artifact-identifying blob out of the plurality of pixel blobs corresponding to the expected pattern of the artifact, the artifact-identifying blob of the mask has a periphery;
performing a smoothing operation on the artifact-identifying blob to introduce a plurality of intermediate values to the mask along the periphery of the artifact-identifying blob;
and
modifying the at least one of the plurality of color characteristics of the artifact in proportion to the end values and intermediate values that represent the pixels of the mask.

5 more elements

Dependencies are inferred from the claim text.