10/11 Notes¶
A fingerprint is an Oriented texture pattern
Oriendted Texture (FFT Method)¶
Orientation (range = [0,pi))
Frequency = frequency of ridges
w(x,y) = Amplitude x cos(2pi x frequency x (xcos(theta) + ysin(theta)))
- Example
- A = 150
- freq = 1/8 (approx)
- theta = pi / 4
for i = 1 : 11 for j = 1 : 11
w(i, j)
What is Amplitude, freq, and theta? (FFT Method)¶
image (spatial domain) – fast fourier transform –> frequency domain == W(u,v)
frequency = distance between center of W and bright spot (impulse) = sqrt((u^)^2 + (v^)^2)
theta = angle of frequency line and x axis = arctan(v^ / u^)
W(u^, v^) = brightest pixel location
Amplitude = color value of W(u^, v^) = abs(W(u^, v^))