US 4,910,694 AGranted

Method for approximating a value which is a nonlinear function of the linear average of pixel data

OwnerLawrence E. Waltherinventor

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Abstract

A system for weighting nonlinear, e.g. logarithmic, pixel data as part of a missing pixel interpolation. This is accomplished to generate a weighted average of the logarithmic intensity values for those pixels which surround the missing pixel in order to approximate the logarithm of the linear average of these pixel values. Two weighting coefficients of unequal value are selected so that their sum equals the quantity one. The larger of the logarithmic values is weighted by multiplying the larger logarithmic pixel value by the larger weighting coefficient, and then by adding to this quantity the smaller logarithmic pixel value which has been multiplied by the smaller weighting coefficient. The result is a weighted logarithmic average which approximates the log of the linear average.

Claims14

Dependent claims

In an imaging system having image signal inputs and image signal outputs, a method of averaging first and second image signal outputs corresponding to first and second different pixels of an image in order to approximate a third image signal output corresponding to a third different pixel of the image, the method comprising the steps of:

a. receiving the first and second image signal outputs wherein said first and second image signal outputs vary from their respective first and second image signal inputs in a nonlinear manner so that at lower levels of the image signal inputs a change in the levels of the image signal inputs generates a first change in the levels of the image signal outputs, and at higher levels of the image signal inputs, a corresponding change in the levels of the image signal inputs generates a second change in the levels of the image signal outputs which is difference from the first change;
b. determining a difference between the level of the first image signal output and the level of the second image signal output;
and
c. generating a weighted average of the nonlinear first and second image signal outputs in order to approximate said third image signal output from an average of the first and second image signal inputs by changing an unweighted average of the first and second image signal outputs by an amount which is a function of the difference between the levels of the first and second image signal outputs.

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