8000 DT (Determine Threshold) not clearly defined · Issue #394 · usnistgov/NFIQ2 · GitHub
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DT (Determine Threshold) not clearly defined #394

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utcke opened this issue Mar 6, 2025 · 0 comments
Open

DT (Determine Threshold) not clearly defined #394

utcke opened this issue Mar 6, 2025 · 0 comments

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@utcke
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utcke commented Mar 6, 2025 •
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6.2.3.1 describes DT as

which is a line positioned at the centre of the local region V used to segment the local region into the ridge and valley regions. Regions with grey levels
lower than DT are classified as ridges. Otherwise, they are classified as valleys

6.2.5.2 uses DT in f) as

x\times DT(1)+DT(0)

So while DT(n) suggest a function of sorts, it is reasonable to assume that DT is a line of the form

y = DT(1)\times x + DT(0)

which is very unusual. Maybe introduce DT, possibly using the standard notation for lines:

DT: y=mx+b

and use m and b? Or, at the very least, introduce it as

DT: y = DT(1) x + DT(0)

or, slightly better

DT: y = DT_1 x + DT_0

BTW, the exact same calculation is performed in 6.2.3.6.e), but there no Formula is given at all (which, personally, I find easier to follow - although it might be a good idea to move Fig. 6 a-c there.
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