Patent ID: 7106913

Claim:
A method of processing n digital source images that represent one and the same real scene and have been acquired with different exposure levels, the said images being made up of pixel matrices, each of which is represented by k components that are each associated with a digital value, for obtaining a final digital image with an ample exposure latitude, the method comprising the following sequence of operations: aligning the source images, constructing a weighted average of the pixels corresponding to all the source images to obtain the corresponding pixels of the final image in accordance with the formula: p f _ ⁡ ( x , y ) = ∑ i = 1 n ⁢ ⁢ w i ⁡ ( x , y ) ⁢ p i _ ⁡ ( x , y ) ∑ i = 1 n ⁢ ⁢ w i ⁡ ( x , y ) where {overscore (p f )}(x,y) is the pixel having the coordinates (x, y) in the final image, {overscore (p 1 )}(x,y), . . . , {overscore (p n )}(x,y) are the corresponding pixels forming part, respectively, of the source images 1, . . . , n, and w 1 (x,y), . . . , w n (x,y) are the weighting coefficients associated, respectively, with the said pixels, wherein the weighting coefficients are scalar values and are chosen in an interval of values comprised between a maximum coefficient and a minimum coefficient by carrying out the following sequence of operations: selecting one and the same component for all the pixels of the source images, the said component being either chosen from among the k possible components or obtained from any linear combination of the said k components, assigning to each pixel of the source images an initial weighting coefficient based on the digital value of the selected component, by using for each image a weighting function that attributes weighting coefficients close to the minimum coefficient to digital values close or equal to the extremes of the range of possible digital values and gradually larger weighting coefficients to digital values forming part of the central regions of the range of possible digital values, selecting in each of the source images a grid that identifies a subset of pixels distributed in a substantially uniform manner over the pixel matrix, subjecting the initial weighting coefficients of the pixels forming part of each selected grid to at least one filtering operation capable of attenuating sudden variations among the initial weighting coefficients of pixels forming part of regions of an image situated close to each other, expanding the filtered weighting coefficients by means of interpolation to obtain estimated filtered weighting coefficients also for the pixels not forming part of the subset identified by the grid, constructing for each pixel a linear combination of the initial weighting coefficient and the filtered weighting coefficient and using the said linear combination as final weighting coefficient for the corresponding pixel of the final image.