Method of improving a digital image

A method of improving a digital image, comprising the steps of:

• providing digital data indexed to represent the positions of a plurality of pixels of a J-row by K-column display, said digital data being indicative of an intensity value I(x,y) for each of said plurality of pixels where x is an index of a position in the J-th row of said display and y is an index of a position in the K-th column of said display;
• convolving said digital data associated with each of said plurality of pixels with a function ##EQU14## to form a discrete convolution value for each of said plurality of pixels, said function satisfying the relationship ##EQU15## where ##EQU16## k is a normalization constant and c is a constant;
• converting, for each of said plurality of pixels, said discrete convolution value into the logarithm domain;
• converting, for each of said plurality of pixels, said intensity value into the logarithm domain;
• subtracting, for each of said plurality of pixels, said discrete convolution value so-converted into the logarithm domain from said intensity value so-converted into the logarithm domain, wherein an adjusted intensity value is generated for each of said plurality of pixels;
• filtering said adjusted intensity value for each of said plurality of pixels with a function that is identical for said plurality of pixels;
• and
• displaying an improved digital image based on said adjusted intensity value so-filtered for each of said plurality of pixels.

A method of improving a digital image, comprising the steps of:

• providing digital data indexed to represent the positions of a plurality of pixels of an J-row by K-column display, said digital data being indicative of an intensity value I.sub.i (x,y) for each i-th spectral band for each of said plurality of pixels where x is an index of a position in the J-th row of said display and y is an index of a position in the K-th column of said display;
• convolving said digital data associated with each of said plurality of pixels in each i-th spectral band with a function ##EQU17## for n=2 to N to form N convolution values for each of said plurality of pixels in each said i-th spectral band, said function satisfying the relationship ##EQU18## where ##EQU19## and, for each n, k.sub.n is a normalization constant and c.sub.n is a unique constant;
• converting, for each of said plurality of pixels in each said i-th spectral band, each of said N convolution values into the logarithm domain;
• converting, for each of said plurality of pixels in each said i-th spectral band, said intensity value into the logarithm domain;
• subtracting, for each of said plurality of pixels in each said i-th spectral band, each of said N convolution values so-converted into the logarithm domain from said intensity value so-converted into the logarithm domain, wherein an adjusted intensity value is generated for each of said plurality of pixels in each said i-th spectral band based on each of said N convolution values;
• forming a weighted sum for each of said plurality of pixels in each said i-th spectral band using said adjusted intensity values;
• filtering said weighted sum for each of said plurality of pixels in each said i-th spectral band with a function that is identical for said plurality of pixels in each said i-th spectral band;
• and
• displaying an improved digital image based on said weighted sum so-filtered for each of said plurality of pixels in each said i-th spectral band.

A method of improving a digital image, comprising the steps of:

• providing digital data indexed to represent positions on a display, said digital data being indicative of an intensity value I.sub.i (x,y) for each position (x,y) in each i-th spectral band;
• adjusting said intensity value for said each position in each i-th spectral band to generate an adjusted intensity value for said each position in each i-th spectral band in accordance with ##EQU21## where S is a whole number greater than or equal to 2 and defines the total number of spectral bands included in said digital data and, for each n, W.sub.n is a weighting factor and F.sub.n (x,y) is a unique surround function of the form ##EQU22## satisfying the relationship ##EQU23## where ##EQU24## and, for each n, k.sub.n is a normalization constant and c.sub.n is a unique constant where N is the total number of unique surround functions;
• filtering said adjusted intensity value for said each position in each i-th spectral band with a common function;
• multiplying said adjusted intensity value for said each position in each i-th spectral band by ##EQU25## where B is a constant;
• and displaying an improved digital image based on said adjusted intensity value for each i-th spectral band so-filtered and so-multiplied for said each position.