Patent ID: 7227991

Claim:
A method for improving the quality of a digital image, the digital image comprising a matrix P of digital values P(x,y), or pixels, each of which is associated on the basis of the position (x,y) with a chromatic component of the red, green or blue type, each of said digital values forming part of a range of possible digital values comprised between a maximum and a minimum number, said method comprising the following operations: establishing a response function f that expresses a relationship between the digital values P(x,y) of the image P and a measure q(x,y) of the quantity of light that produced said digital values, extracting from the image P the matrix G of the pixels associated with the green chromatic component obtained from P by discarding the pixels associated with the red and the blue component, subdividing P into a plurality of adjacent and not overlapping regions, selecting the visually important regions of G, establishing a digital value Mean v substantially at the center of the range of the possible digital values, modifying the image P to obtain a corrected image P T by performing a translation of the digital values of P by means of the inverting the response function f in such a manner as to make the mean of the digital values of G forming part of the important regions coincide with Mean v , characterized in that the important regions of G are selected by performing the following sequence of operations: establishing a digital value Mean v substantially at the center of the range of the possible digital values, obtaining from the plane G a plane G T by performing a translation of the digital values of G by inverting the response function f in such a manner as to make the mean of the pixels of G substantially coincide with Mean, subdividing the plane G T into regions corresponding to the regions of G, assigning to every region of G an index of visual importance V calculated on the basis of at least one contrast measure D and at least one focus measure F of the pixels of the corresponding region G T , establishing a threshold value V t , and selecting the regions of G whose index of visual importance V is greater than V t .