Patent ID: 7646931

Claim:
A method performed by a computer configured as a digital image adjustment computer of processing a digital image, the method comprising: with the computer configured as the digital image adjustment computer, adjusting exposure data for the digital image, wherein the exposure data comprises luminance values represented in a luminance value histogram for pixels in the digital image, and wherein adjusting the exposure data comprises: selecting between performing an adjustment for distribution of histogram values, an adjustment for underexposure, and an adjustment for overexposure; and performing the selected adjustment; with the computer configured as the digital image adjustment computer, producing exposure adjustment data for the digital image based on the adjusting; with the computer configured as the digital image adjustment computer, storing the exposure adjustment data in a look-up table; and with the computer configured as the digital image adjustment computer, storing the look-up table in a digital image file, wherein the storing the look-up table in the digital image file facilitates archiving an original version of the digital image wherein performing the adjustment for distribution of histogram values comprises: determining a MaxLevel parameter as a maximum luminance value in the histogram; determining a Scale parameter associated with the histogram; determining a Center parameter associated with the histogram; and performing a histogram stretch on the histogram, wherein the histogram stretch comprises mapping the luminance value Y of each pixel in the digital image to a new luminance value Y′ according to the following equation: Y ′ = Scale * ( Y - Center ) + MaxLevel 2 ; wherein performing the adjustment for underexposure comprises: determining the MaxLevel parameter; and applying a positive gamma curve with a Gamma parameter to the histogram to increase luminance values, wherein the applying the positive gamma curve comprises mapping the luminance value Y of each pixel in the digital image to a new luminance value Y′ according to the following equation: Y ′ = MaxLevel * ( 1 - ( MaxLevel - Y MaxLevel ) Gamma ) ; and wherein performing the adjustment for overexposure comprises: determining the MaxLevel parameter; and applying a negative gamma curve with a Gamma parameter used to decrease luminance values to the histogram, wherein the applying the negative gamma curve comprises mapping the luminance value Y of each pixel in the digital image to a new luminance value Y′ according to the following equation: Y ′ = MaxLevel * ( Y MaxLevel ) 1 Gamma .