Abstract: Brightness and color tone shift distortion of captured images by a non-ideal lens can be compensated by applying an inverse transfer function to the captured image. An estimate of the lens transfer function can be measured based on a radius from a center of the lens. The lens transfer function can be measured by capturing a flat field image. The center of the lens can be determined based on a relative brightness maximum. The relative brightness of the captured flat field image can then be measured as a function of radius to generate a lens response curve. Separate response curves can be measured for each color component. A correction curve can be determined as the inverse of the response curve. The correction curve can be applied to subsequent captured images to compensate for lens degradation.

Abstract: Automatic white balance of captured images can be performed based on a gray world assumption. Initially, a flat field gray image is captured for one or more reference illuminations. The statistics of the captured gray image are determined and stored for each reference illumination during a calibration process. For each subsequent captured image, the image is filtered to determine a subset of gray pixels. The gray pixels are further divided into a one or more gray clusters. The average weight of the one or more gray clusters is determined and a distance from the average weights to the reference illuminants is determined. An estimate of the illuminant is determined depending on the distances. White balance gains are applied to the image based on the estimated illuminant.

Abstract: A method of processing an image includes selecting, for each of a plurality of picture element values in at least a portion of the image, one among a plurality of offset values. For each of the plurality of picture element values, an index value is obtained based on (A) the selected offset value and (B) a portion of the picture element value. For each of the plurality of picture element values, an entry is retrieved from a lookup table according to the corresponding index value.