Patent Document ID: 5581370
Application ID: 08461913
Patent Status: 1

Claim One:
1. A method of improving the contrast in a natural scene image recorded as a set of electronic signals, including the steps of: assuring that at least one component of the original electronic signal forming the natural scene image is defined with a signal describing intensity of the image; from the intensity component of the electronic signals, deriving a set of local histograms signals, each describing the population of signals at possible intensity levels within the image for a region of the image; selecting a subset of the local histogram signals as representing a maximum dynamic range of the natural scene image; determining locations, by region, of the black point and white point within the electronic signals of the image; assuring that the histograms representing regions in which the black point and white point occur are members of the subset of local histogram signals, and if not, adding them thereto; combining the subset of local histograms with a selected weighting function to generate a relevant histogram; operating on the relevant histogram signal with a filter that has the characteristics of reducing strong peaks and valleys in the signal; using the filtered histogram signal, deriving a tonal mapping of input signals to output driver signals; for each electronic signal forming the natural scene image, mapping the electronic signal to an output driver signal, using the tonal mapping derived.