Patent ID: 7684639

Claim:
A method for digital image contrast enhancement, said method comprising: a) performing a histogram analysis of an image; b) skipping contrast enhancement when said histogram analysis shows that said image comprises a sufficient number of bright pixels and an insufficient number of dark pixels; c) performing a first contrast enhancement comprising applying a final luminance map derived from blending a piecewise-linear luminance map with a gamma correction curve when said histogram analysis shows that said image has many very bright pixels; d) performing a second contrast enhancement comprising applying a final luminance map derived from blending a piecewise-linear luminance map with a gamma correction curve when said histogram analysis shows that said image has many very dark pixels; e) performing a third contrast enhancement comprising applying a final luminance map comprising a brightness offset when said histogram analysis shows that said image does not have many very dark pixels and said image does not have many very bright pixels; f) wherein said image has a sufficient number of bright pixels when one of the following conditions is met: i) the top three histogram bins contain more than 40% of the total pixels in the image, or ii) the top ⅛ to ½ of the histogram bins contain more than 30% to 50% of the total pixels in the image; and g) wherein said performing a first, second or third contrast enhancement is performed by a processor and a memory.