Patent ID: 8565549

Claim:
A contrast enhancement method for an image having a plurality of pixels, the method comprising: extracting at least one sub-band image from the image, comprising detail information at a predetermined spatial scale; determining a first gain value for each pixel, based on pixel values of one of the image and the at least one sub-band image; determining a second gain value for each pixel; modifying the first gain value for each pixel using the respective second gain value; and generating an enhanced image by applying the modified first gain values to respective pixels of at least one sub-band image and combining the result with the image, wherein determining the first gain value for each pixel comprises: estimating a dynamic range of the pixel values in a neighbourhood of that pixel; and setting the first gain value in inverse relation to the dynamic range, and wherein determining the second gain value for each pixel comprises: estimating a probability distribution of the pixel values in the neighbourhood; and determining the second gain value based on the amplitude of the peak of the probability distribution.