Method for improving images applicable to fingerprint images

Method for processing a finger image acquired by a fingerprint sensor of direct view type and comprising at least one fingerprint in order to implement an authentication or identification of an individual by comparison of fingerprints, said image comprising a set of pixels, each pixel being associated with a grey level, the method comprising a step of segmentation of the image to generate a modified image only containing regions of the image having an alternation of bright zones and dark zones at a frequency greater than a minimum frequency, said step of segmentation comprising:

• the allocation, to each pixel of the image, of a frequency response level, corresponding to a frequency of alternations of bright zones and dark zones in the vicinity of the pixel, by evaluating the variabilities of the grey levels of the pixels contained in a window of determined size positioned around each pixel,
• the definition of regions of the image by grouping together neighbouring pixels of same frequency response level previously allocated to each pixel,
• the determination of a threshold frequency response level,
• selection, from the regions of the image defined previously by grouping together neighbouring pixels of same frequency response level, of regions of which the pixels have a frequency response level greater than or equal to the threshold frequency response level, and
• the generation of a modified image only comprising, among the regions of the image defined previously by grouping together neighbouring pixels of same frequency response level, regions of which the pixels have a frequency response level greater than or equal to the threshold frequency response level,
• a step of authentication or identification of an individual by comparison of fingerprints on the basis of the modified image.