Determination of the orientation of the ridges of a fingerprint
AssigneeSTMicroelectronics S.r.l.
InventorChristel-Loïc Tisse
Life of this patent
Estimating the term…
Abstract
A method and a circuit for determining the orientation of ridges of a digital image representing a fingerprint or the like, including for each image pixel, calculating a quantity taking into account the neighboring pixels in all directions, and of bidirectionally scanning the image line by line.
Claims11
A method for determining orientations of ridges of a digital image representing a fingerprint, the digital image being stored as a matrix in a memory, and the digital image having a plurality of lines of pixels and a plurality of side edges, each of the pixels having a stored pixel grey level, the method comprising:
- bidirectionally scanning the stored digital image by scanning the lines of pixels line by line for the pixel grey levels, wherein bidirectionally scanning comprises scanning a first pixel line in a first scanning direction and scanning a second pixel line in a second, reverse scanning direction;
- for each pixel, executing an orientation calculation using operators, and assigning an orientation quantity to the pixel, by taking into account pixel grey levels of neighboring pixels lying along a plurality of directions, each direction in the plurality of directions having a first direction extending away from the pixel and a second direction extending away from the pixel, the second direction being opposite to the first direction.
A device for determining orientations of lines in a digital image, comprising:
- a plurality of bidirectional matrix shift registers configured to allow parallel loading and unloading of words for each matrix shift register, each word representing a pixel grey level;
- a first wired logic circuit that is configured to receive, as inputs, words unloaded in parallel from the matrix shift registers;
- wherein the wired logic circuit is configured to calculate the orientation of a ridge at a pixel location by using the pixel grey levels of neighboring pixels surrounding said pixel location to calculate an orientation quantity , and is further configured to assign the orientation quantity to said pixel.
A method for determining orientations of ridges of a digital image representing a fingerprint, the digital image being stored in a memory, the digital image comprising a plurality of lines of image pixels, the method comprising:
- bidirectionally scanning the image line-by-line for pixel grey levels, wherein bidirectionally scanning comprises scanning a first pixel line in a first scanning direction and scanning a second pixel line in a second, reverse scanning direction;
- and
- for each image pixel, using a wired logic circuit to calculate an orientation quantity taking into account grey levels of neighboring pixels in a plurality of directions.
Dependencies are inferred from the claim text.