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Marco Realacci 2025-01-14 01:30:56 +01:00
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.obsidian/workspace.json vendored
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@ -45,7 +45,7 @@
"file": "Biometric Systems/slides/LEZIONE11_Fingerprints.pdf", "file": "Biometric Systems/slides/LEZIONE11_Fingerprints.pdf",
"page": 35, "page": 35,
"left": -14, "left": -14,
"top": 341, "top": 491,
"zoom": 1.0875 "zoom": 1.0875
}, },
"icon": "lucide-file-text", "icon": "lucide-file-text",

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Biometric Systems/notes/11. Fingerprints.md
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@ -100,7 +100,7 @@ Once a fingerprint has been segmentated we can start extracting **macro-features
![[Pasted image 20241127135348.png]] ![[Pasted image 20241127135348.png]]
##### Directional map ##### Directional map
The local orientation of the ridge line in the position [i, j] is defined as the angle $\theta(i,j)$ formed by considering the horizontal line at that point, and a point on the ridge line sufficiently closer to [i, j]. ~~The local orientation of the ridge line in the position [i, j] is defined as the angle $\theta(i,j)$ formed by considering the horizontal line at that point, and a point on the ridge line sufficiently closer to [i, j].~~
![[Pasted image 20241127224325.png]] ![[Pasted image 20241127224325.png]]
- most approaches use a grid measure (instead of measuring at each point) - most approaches use a grid measure (instead of measuring at each point)
- the directional image D is a matrix in which each element denotes the average orientation of the ridge (of the tangent to the ridge) in a neighborhood of $[x_{i}, y_{i}]$ - the directional image D is a matrix in which each element denotes the average orientation of the ridge (of the tangent to the ridge) in a neighborhood of $[x_{i}, y_{i}]$