find the circularity of diamond, inverted triangle and octagon shape
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hi,currently I working with road sign sign detection, based on the observations from regionprops of matlab value, to detect circular shape, the circularities should be < 1.2, for square shape, circularities <1.6 and triangle shape should be <1.8
Can I know what is the circularities values for diamond , inverted triangle and octagon shapes respectively?
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Image Analyst
2012-10-15
Circularity is obtained by solving for the radius in terms of both the perimeter and area for a circle:
P = 2*pi*r
r = P/(2*pi)
A = pi*r^2
r = sqrt(A/pi) = P/(2*pi)
A/pi = P^2 / (4*pi^2)
1 = p^2 / (4*pi*A) = circularity
circularity = Perimeter^2 / (4 * pi * Area)
To find out what it is for those shapes, just create those shapes, and measure the perimeter and area.
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